Latest News

Latest News

19 600 Farmers Receive Command Agric Inputs


 More than 19 600 farmers have so far received adequate inputs from Government’s specialised import substitution maize (Command Agriculture), the Zanu-PF Politburo heard yesterday.


Most farmers have started planting while others are intensifying land preparations.



Compiled By:

Robson Chihumba

AGRITEX: Agronomist

Alfios Mayoyo-MAMID Economist


Edited by:

Godfrey Tore: AGRITEX: Principal Agricultural Extension Specialist

Rutendo Nhongonhema: AGRITEX: Acting Chief Agricultural Extension Officer





Date of Publication:April 2014

Place of Publication:Agritex Harare


The Ministry of Agriculture, Mechanisation and Irrigation Development would like to thank Mercy Corps for the support in the production of this book. Many thanks also go to all resource persons who worked tirelessly in the production of this Resource Manual. Such collaboration between the government and non-governmental organizations need to be commended as it has proved over the years that it is an effective way to reach out to farmers with a full package of information.



Acknowledgement:. 2

Contents. 3


1.1        Introduction. 5

1.2        Maize Growth and Development 5

1.3        Land selection. 12


2.1        Water Requirements. 14

2.2        Temperature. 16

2.3        Heat Units. 16

2.4        Rotations. 17

2.5        Intercropping. 17

2.6        Land Preparation. 17

2.6.1          Conventional Tillage. 17

2.6.2          Conservation tillage. 18

2.7        Seed selection. 19

2.8        Planting Date. 19

2.9        Planting Techniques. 20

2.10     Spacing. 21

2.11     Plant Population. 21

2.12     Fertilization. 22

2.13     Soil sampling. 22

2.14     Lime. 23

2.15     Major Nutrients. 24

2.16     Compound fertilizers. 26

2.17     Top dressing. 27

2.18     Fertilizers Application Methods. 28

2.19     Factors having a negative effect on a good crop stand. 29

2.20     Maturity. 29

2.21     Grain yield. 30


3.1        Weed management 31

3.2        Weed control methods. 31

3.2.1          Manual method (Hand). 31

3.2.2          Mechanical weed control 31

3.2.3          Cultural control 31

3.2.4          Chemical control 31

3.3        Pests Management 33

3.4        Diseases Control 39

3.5        Storage Pests. 41

3.6        Control of storage pests. 42

3.7        Grain treatment method. 42


4.1        Timing for harvesting. 44

4.2        Harvesting methods. 44

4.2.1          Manual harvesting. 44

4.2.2          Direct Dehusking. 45

4.2.3          Dehusking on Stacks or Windrows. 45

4.3        Management Practices to Minimize Losses. 45

4.4        Combine Harvesting. 46

4.5        Storage. 46

4.6        Marketing. 46

4.7        Exports and imports. 47









1.1      Introduction

Maize (Zea mays L.) is the most important grain crop in Zimbabwe and is produced throughout the country under diverse environments. Successful maize production depends on good production practices such as proper variety selection, effective pests, disease and weed control, good water and nutrition management as well as early planting. Maize is grown mainly in summer where there are favourable conditions such as water and temperature for good growth and yields. Maize can also be grown in winter under irrigation where frost is not a challenge. Maize is Zimbabwe’s staple for human consumption and can also be used in formulation of stock feeds for cattle, poultry, and pigs. Maize is grown across all farming sectors as well as in Peri-urban areas for both household consumption and for sale. Maize can be marketed anywhere within Zimbabwe.

1.2      Maize Growth and Development

To produce high maize yields it is important to have an understanding of how maize grows and develops for timely manage­ment decisions. The table below gives a summary of development for maize However it is important to note that this is an indication and growth rates vary among hybrids and with growing conditions.

Maize growth stages can be grouped into four major stages which are:

  • Germination, Emergence and Early Growth
  • Spikelet Initiation and Vegetative Growth
  • Flowering and Pollination
  • Grain-fill and Maturation




Table1: Developmental stages of maize

Days after Planting

Development Status of Corn Plant

Management Hints


Seed germination.

This process will take place in 7 - 10 days under warm (20 - 30°C), moist conditions, but can take 14 days or longer under dry, cool temperatures. Depth of planting will also affect emergence

  • Early planting must be as shallow as possible within certain limits. Deep planting means lower soil temperatures with slower germination and an uneven stand.
  • Place fertilizer in bands at least 5cm deeper as well as 5cm away from the seed to prevent chemical burn. This is crucial especially on sandy soils.
  • Do not apply more than 60 - 70 kg nitrogen (N) plus potassium (K) in the band, as this can lead to chemical burn.
  • Prevent the soil from forming a crust, or rectify the problem immediately. Treat with registered insecticides to reduce soil insect damage.


Seedling emergence. Primary roots developing.


Two leaves expanded. Primary roots functioning. Nodal (permanent) roots forming. Plant making food.

  • A weed free seedbed after emergence gives the seedling the best chance for good establishment.
  • Thinning of weaker plants can be necessary in cases where there are two or more plants per planting station.
  • Gap filling can also be done at least within two weeks after emerge.
  • Any nutritional deficiencies must be corrected immediately at this stage.
  • Weed control is very important to ensure that the small slow-growing plant can establish itself well



Four to six leaves expanded and a new leaf will unfurl every third day thereafter. Remaining leaves and nodal roots developing. Growing point near soil surface. Although the total number of leaves and lateral branches are determined at this time, the growing point is still below the soil surface. Initiation of the tassel also takes place at this stage.



Six to eight leaves expanded. Tassel developing. Growing point 5-7cm above ground.

Up to this stage, and to 6 weeks after emergence, the plants can withstand moderate moisture stress without a later significant loss of yield.

  • The ideal time to apply a nitrogen top dressing is before the eight leaf stage.
  • All nutritional deficiencies must now be rectified to ensure that the final yield potential determined, during the twelve leaf stage, is not influenced negatively.
  • Where the surface of the soil has compacted alight tillage cultivation can be done to aerate the soil. Cultivation must be very shallow and away from the roots to avoid any root damage.



Ten to 12 leaves expanded (bottom 4 lost). Ear shoots developing (maximum number of potential kernels on primary ear determined). Stalk growing fast. Brace roots developing. And the plant will be solely dependent on photosynthesis for its organic nutrients. The growing point will now be about 50 - 75 mm above the soil surface. Tillers will form from nodes below the surface.



Fourteenth leaf expanded. Rapid stalk growth continuing. Tassel not visible but nearly full size. Top two earsshoot developing rapidly. Silks forming at base of top ear shoot.

This is a critical stage as the potential of the ear(s) is determined. Moisture and nutrient deficiencies will greatly reduce the size of the cobs and kernels.

Any leaf area loss will also markedly reduce the yield potential.

  • With maize under irrigation it is of vital importance to prevent any moisture stress two weeks before and two weeks after tasseling.
  • Hail damage at this stage, especially during tasseling can mean a total crop failure. The factory of the plant, which is the leaves, is now fully developed. The plant cannot recover from any form of damage.
  •  In unfavourable conditions (for example, very high temperatures or cold, rainy weather), there may be no pollen-shed.
  • In maize lands especially lands planted late in the growing season, second generation stalk borer can appear. This is normally a severe infestation and leads to big yield losses and poor grain quality due to Fusarium cob-rots. An aerial application of the correct chemical will be needed to solve this problem.
  • The moisture as well as fertilizer requirement of the plant is very high at this stage. Strong root development will assist the plant to withstand very wet conditions.
  • Deep tilling operations must be avoided as this will enhance stem and root rot infection.


Sixteenth leaf expanded. Five to six bottom leaves lost. Tassel emerging. Top ear shoot and silks elongating (second ear normally does not fully develop).


All leaves expanded. Tassel emerged. Silks emerging. Pollination beginning. This is for early planted maize. Maize planted late may have emerged silks and tassels in 45–50 days. Nutrients and water are rapidly used as the stem begins to thicken and elongate between the ninth and twelfth internodes. Prop (anchor) roots begin to emerge, and general root growth is rapid. At this stage, the roots can extend downwards to a depth of 1.0 m and extend sideways to 0.8 m.



Pollen shed complete. Kernels in blister stage. The maize plant is monoecious, bearing male flowers in the tassel and female flowers on the lateral ear shoots of the same plant. . Most tassels shed pollen for 5–8 days, with pollen production reaching a peak around the third day


Kernels in dough stage and rapidly increasing in weight. Carbohydrates and nutrients rapidly accumulate in the developing kernels in the form of clear fluid.



Kernels at 50% milk stage. The milk stage begins 3 weeks after silking. The kernels are filled with a white, milky fluid. The fluid has high sugar content and the kernels are most suitable for consumption as fresh maize. Following the milk stage, the sugar content decreases and the starch content increases. Also, water content decreases as dry matter content increases.




Kernels in early dent stage.

The moisture requirement of the plants now very low, but drought will still influence the yield and grain quality.  With an irrigated crop, irrigation can cease when 80% of the husk leaves have turned brown.   The final yield has been established when the maize plant has reached physiological maturity.


Kernels fully dented. Physiological maturity is the last stage of the grain filling period and takes 15to 20 days while the moisture content of the grain decreases from 50% to below 40%. There are no soft portions of grain at the tip of the kernel (this is where the kernels are joined to the cob) and the hard starch line, also known as the milk line, has moved through

the kernel from the crown of the kernel to the attachment on the cob


Ear mature (black layer formed on 75% of kernels in middle of ear). The colour of the husk leaves that cover the cob are 70% to 80% light brown. In contrast to grain filling, the kernels at the tip of the cob will mature before the kernels at the base.


The moisture content of the grain is now about 35%.The mature grain needs to dry down before it can be harvested and stored.

Kernels ready for harvesting at 12-14% moisture.

Depending on hectares and expected yield decisions on whether mechanical or manual harvesting are made.

Storage by now should have been prepared.


1.3      Land selection

 Maize can be grown on a wide range of soils with varying success.

  • The heavy-textured soils (sandy clay loams and heavier soils), which are inherently high in fertility, are considered to be the most suitable.
  • Good maize yields can also be achieved on the lighter-textured soils by applying the correct levels of fertilizer and under reasonable climatic conditions.
  • Heavier soils have a higher water-holding capacity than lighter soils; although they need more water to reach field capacity. They conserve more moisture hence they can sustain growth for a long period during drought or at the season-end than sandy soils.
  • The soil type must be taken into account when planning production. Heavy soils tend to extend the end of the growing season while sandy soils can often be planted earlier, particularly when 'water-planting' is used.
  • Maize is sensitive to water-logging and poorly-drained or badly-aerated soils therefore such soils should be avoided.



2.1      Water Requirements

  • Maize needs 450 to 600 mm of water per season, which is mainly acquired from the soil moisture reserves. About 10-16 kg of grain is produced for each millimetre of water consumed. . A yield of 3 152 kg/ha requires between 350 and 450 mm of rain per annum. At maturity, each plant will have consumed 250 l of water of water in the absence of moisture stress. The total leaf area at maturity may exceed one square metre per plant. Variations in rainfall are the main cause of differences in maize yield. Farmers should have a good understanding of the rainfall pattern that occurs in their locality.
  • The total amount of rainfall that falls during the season is only one aspect that should be considered. Rainfall distribution, season length and quality must also be taken into account.

Initially the moisture requirement is low and builds up to a maximum during the flowering period of the maize plant. Thereafter the moisture requirement progressively decreases until the plants are physiologically mature. In practice it is important to remember that the moisture requirement is at its highest approximately two weeks before and two weeks after pollination.



The graph shows that the most sensitive stage is during pollination. Pollen is pure protein and thus requires a lot of energy for its production.  During this period, moisture requirements are at peak and under high population the requirements can be as high as 10mm/day or more


2.2      Temperature

Maize is a warm weather crop and is not grown in areas where the mean daily temperature is less than 19 ºC or where the mean of the summer months is less than 23 ºC. Although the minimum temperature for germination is 10 ºC, germination will be faster and less variable at soil temperatures of 16 to 18 ºC. At 20 ºC, maize should emerge within five to six days. The critical temperature detrimentally affecting yield is approximately 32 ºC. At temperatures below 6 ºC and above 45 ºC, photosynthesis stops. Frost can damage maize at all growth stages and a frost-free period of 120 to 140 days is required to prevent damage. While the growth point is below the soil surface, new leaves will form and frost damage will not be too serious. Leaves of mature plants are easily damaged by frost and grain filling can be adversely affected. Under adverse heat stress conditions, the leaves may redden and become scorched. The optimum temperature for maize is between 20-30oC for germination and growth.


2.3      Heat Units

These are one of the most important environmental factors affecting the growth of the maize plant. Maize cannot develop from one stage to the next advanced stage without receiving the necessary heat units. Maize is a short day crop which means that as the days shorten (as we approach winter) the less heat units available per day and the quicker grain filling comes to an end.  This results in low yields and poor grain quality. Symptoms seen in late planted crop are purpling of leaves indicating the reduced rate of sugar translocation from the leaves to the cob. This is why the late planted maize mostly gives poor yields.


2.4      Rotations

Maize can be grown successfully in a number of rotations. It fits in well with Soybean, cotton, tobacco and vegetable crop rotations. The maize will benefit from the residual nitrogen left in the soil by the legume crop or as excess nitrogen from the preceding crop. This nitrogen is available to the crop in its early stages.

2.5      Intercropping

Maize can be intercropped with legume crops such as cowpeas or Bambara nuts. These crops can be grown between rows or in rows between crops. The maize crop will benefit from nitrogen fixed by the legume crops. However intercropping may make it difficult to weed control using chemicals and cultivation methods.


2.6      Land Preparation

Land can be prepared under conventional and conservation methods. Conventional methods involve turning and inverting the soil by the use of disc harrows, mouldboard ploughs or rippers. Conservation methods involve different practices which have minimum soil disturbance. Conservation agriculture may use ripper tines, sub soiler or hoes.

2.6.1   Conventional Tillage


Ploughing is done using a tractor or cattle drawn plough.  This implement is used to turn soil up to 25cm depth and is particularly useful on heavier well-structured soils. Mould board ploughs are not recommended on sandy soils, because poorly-structured units which may exist, can be destroyed and wind erosion be promoted. Ploughing inverts and turns the soil leaving large clods which may make it difficult for planting


Discing is done using a disc harrow. This equipment has a slicing effect and does not cut deep into the soil. Disking is done for purposes of creating a seedbed for planting. Large clods created by the mouldboard are broken down. Stalks of the previous crop are also cut. Disking can be done in winter or towards planting. 

Advantages of conventional tillage

  • There is good soil inversion and this improves grass and weeds decomposition as well as roots penetration.
  • Conventional tillage equipment/implements are designed such that they can be adjusted to achieve different effects on the soil depth and tilth.
  • Winter ploughing is the best time to perform primary tillage. The soil will be moist giving enough time for crop residue decomposition.


  • It is expensive as it calls for more than one land operation.

Soil texture and structure is destroyed resulting in reduced water and root penetration


2.6.2    Conservation tillage

This is also referred to as minimum or reduced tillage. Of recent the term Conservation Agriculture (CA) has been introduced. The aim is to disturb the soil only at the planting station or row. Crop residues from the previous crop are left on the soil surface as mulch. Implements for conservation tillage are the ripper or sub-soilerand simple hoes for small holder farmers.


  • This results in improved water and soil conservation.
  • Reduces costs on tear and wear of machinery hence low total cost of land preparation.
  • Produces a significant improvement in soil fertility, structure and the final crop yield.
  • Planting can also be achieved by direct seeding.


  • With the coming in of Conservation Agriculture (CA), there is high initial cost of acquiring specialized planting equipment.
  • The techniques of minimum tillage require high management skills during the initial years of implementing.
  • Weed pressure is high during the initial year practicing CA.


2.7      Seed selection

Growers have only one chance to make the right decision on the maize seed to use each year. There are differences among hybrids in yield potential, maturity, standability, disease resistance, grain quality, and adaptability. Farmers should seek information on these from their local extension worker or the particular seed company.

Primary selection criteria when selecting a hybrid include the following:


2.8      Planting Date

In Zimbabwe maize yield is mainly a function of planting date. Maize growth and development are primarily dependent on temperature rather than day length. Successful germination requires a morning soil temperature of above10° Celsius at a 5cm depth for three consecutive days.

Planting dates for maize begin in late October and proceed to late December.

Advantages to early planting include the following:

• The length of the growing season is increased.

  • More stored soil moisture

• Higher yield potential

• Lower temperatures during pollination the pollination period occurs earlier, and may be complete before the mid-season drought which occurs in most areas.

• Longer day lengths at pollination

The greatest number of heat units fall during October, November and December hence, early-planting will allow greater dry matter accumulation in the plants, provided moisture is not limiting

• Less insect and disease damage

Plants will have a more vigorous root system if planted before the on-set of the effective rain.When moisture is adequate, plant the seeds 3-5cm deep. When soil moisture is deeper than 6cm, waiting for a rain may improve stands. In cold sandy soil, the depth may need to be closer to 3-4cm. Germina­tion time and emergence will vary with moisture and temperature from 5 to 30 days. Maize can be hand planted or machine planted. In hand planting 2 to 3 seeds can be dropped per planting station and then covered. If using a maize planter it is important to calibrate it correctly.


2.9      Planting Techniques

a) Rain planting

This involves planting with the first effective rains. Farmers should be well prepared with all the inputs so as to plant as soon as the soil has field moisture capacity.

b) Dry planting

The land should be fully-prepared and planted at least 2-3 weeks prior to receiving the first effective rainfall. This ensures that the crop is established early.

c) Water planting

Irrigation is used to put the soil to field moisture capacity and then establish a crop early before the effective rains. Long season varieties are ideal under this method. Effective rainfall and subsequent rains will help bring the crop to maturity.


2.10    Spacing

Farmers are advised to adopt a spacing which is compatible with other mechanical operations e.g. weeding, fertilization and harvesting. Inter-row spacing commonly used in Zimbabwe ranges from 75- 90cmwith an in-row spacing of 20-30cm. Spacing will depend on the variety grown and agro-ecological conditions.


2.11    Plant Population

Choosing and achieving optimum plant populations are two of the most important factors in maize production. The optimum plant population at which to grow a particular hybrid will depend on:

  • The type and stature of the plant,
  • Climatic conditions,
  • Soil type
  • Rainfall and rainfall pattern
  • Variety

Higher plant populations may be used when in high rainfall areas and lower plant populations in drier areas. As plant population increases, so does the incidence of lodging; thus optimum populations are limited by lodging even under favourable conditions. In high rainfall areas, plant populations of between 40 000 - 55000 plants/ha are recommended. In marginal areas, plant populations of 32 000 - 40 000 plants/ha are recommended.


Research has shown that increased yields can be obtained with more narrow rows at high plant populations. This allows plants to exploit more moisture, nutrients, and light due to greater space between plants. It also helps weed control by shading the ground more quickly. Row widths of 75–90cm are adequate for high yields. In some studies, twin rows yields have shown to be 5–10% higher than single rows; however, water and other factors usually limit yield more than plant population.


For farmers using direct seeders whether in conventional or conservation farming calibration of the seeder is important to achieve the desired plant population. To check the plant population using a seeder the number of kernels in one row for the indicated distance (Table 6) and multiply this number by 1,000 to get population/acre. Check several rows to be certain each planter unit is working properly. It is always best to double-check the planter to ensure seed drop is providing the desired populations.


2.12    Fertilization

A good fertility program should be based on the soil fertility level as determined by soil tests and yield goal. Fertilization programs not based on soil tests may result in excessive and/or sub-optimum rates of nutrients being applied. Soil samples should be taken around May / June each year to monitor the fertility level. It is advisable for farmers to take their soils for soil analysis. In the absence of soil analysis general fertilizer recommendations are made. High rainfall areas require more fertilizer than low rainfall areas.


2.13    Soil sampling

There are a number of factors to consider when collecting a representative soil sample.

  1. Soil sample prior to cultivation. The normal cultivation depth for a maize crop is approximately 150 mm therefore the soil sample should be taken to this depth. Soil pH and nutrient levels decrease as soil depth increases. The decrease can be especially large in low fertility environments or where soil fertiliser application has been limited. Ensure that the person making the fertiliser recommendation is informed if the cultivation depth will be greater than the sampling depth as additional lime and fertiliser may be required.
  2. Choose soil sampling sites carefully. If the area has recently been in maize, ensure that the samples are collected representatively across the field and from the central area between the rows of stubble. The main reason for this is that if the sample is inadvertently taken from an area where the starter fertiliser was banded, any residual product will give elevated readings. This can be significant since 250 kg/ha of banded starter fertiliser could be equivalent to as much as 3.75 tonnes of the same product broadcast per hectare.
  3. Ensure that the soil sample is free of plant or crop debris and large root pieces. Plant material can distort nutrient levels and the physical characteristics of the soil as expressed in the laboratory report.
  4. Deep N soil test after planting and before applying additional nitrogen. Take a deep N (60 cm) soil sample 2 - 4 weeks after planting to determine whether your crop requires any side dress nitrogen.

 The local extension worker can help in interpretation of the soil test.

Most soils in communal are naturally acid and infertile. There­fore, substantial quantities of lime and fertilizer are required for optimum yields. Maize grown for silage requires more nutrients than maize grown for grain because cutting silage removes all of the nutrients from the field in the above-ground plant parts.


2.14    Lime

Most soils in the country have not been limed for a long time. Fields that have been planted to maize continuouslyover the years or are rotated with other grass crops may become acid due to (1) use of high amounts of nitrogen that is acid forming, (2) leaching of calcium and magnesium, and (3) nutrient removal by the crops, . Maize grows well in soil with a pH of 5.5–6.5. Soil with a pH below 5.2 can fix plant nutrients, especially phosphorus, in forms unavailable to plants. Also, since most bacteria cannot live under very acid conditions, liming increases bacterial activity that breaks down soil organic matter to make soil nitrogen and other nutrients more available to the crop. Likewise, herbicide activity of triazine herbicides is most effective when the soil pH is between 5.8 and 6.5.

  • On heavy soils pH should not be allowed to drop below 5.0.
  • It is recommended that fields be limed once in three years.
  • General recommendation is 600- 1000kg/ha of limes
  • If the soil is strongly acidic comparatively large applications of lime are required, ½ to 2/3 of the recommended lime should be applied in the first season and the remainder in the following season.
  • It is important that the lime should be incorporated throughout the plough Zone (30 cm). It is recommended also that it be applied at winter ploughing to give it time to react with soils before planting. 

NB manure & ash have liming effects on soils but application rates may require chemical analysis.


2.15    Major Nutrients

The maize plant produces high dry matter yields and therefore has a high requirement for nutrients especially nitrogen (N), phosphorus (P) and potassium (K). Maize has a deep rooting structure (up to 1.8 m) and this allows it to utilise nutrients which have dropped below the root zone of shallow rooted crop and grass species.

When determining crop fertiliser requirements always obtain a recent, representative soil sample. Don't apply more fertiliser nutrients than you need. As well as being expensive, applying excess fertiliser above crop requirements can result in nutrient losses to our waterways.

Table 2. The nutrient requirement kg/ha for 15t/ha dry matter maize crop are:

Soil Fertility (P & K Index)





















The graph shows MPK uptake during the growth of a maize plant (Pannar Handbook, 2010). The uptake increases as the crop grows with highest uptake before and after flowering.


a) Nitrogen (N)

Nitrogen is the most limiting nutrient for high yields. The available N content of most soils in Zimbabwe, and of all hardly managed soils, is low because there is little organic matter present. Application of nitrogen fertilizer is therefore always necessary for good crop yields. Nitrogen is required throughout plant growth. When nitrogen is deficient from an early stage the plants are small, pale, slow-growing and have weak stems. About 20–25% of the nitrogen needs of the crop can


Table 3. Nitrogen application is mostly based on the expected yield. The table below gives an indication of nitrogen needs vs. yield

Yield potential (t/ha)










Nitrogen Application (kg/ha)










Phosphorus (P)

Virgin soils in Zimbabwe are inherently deficient in phosphate but as P accumulates in the surface layers from regular applications of fertilizer or manure, the P status of well-managed soils is normally medium to high. Large amounts of fertilizer may be required on virgin soils but thereafter only decreased applications are needed. In the early stages of growth the young plants will absorb P mainly from fertilizer placed near the seed, but during later growth most P is taken up from that distributed widely throughout the rooting zone. In some hybrids deficiency causes a purpling of the lower leaves.

Potassium (K)

Most virgin soils have sufficient K for maize crops. Deficiencies will only occur after prolonged cropping with insufficient fertilizer, or where soil reserves are depleted by stover being taken from the land or by crop removal in high-demand drops such as forage or soya. Thus maintenance applications of K are all that is normally required.  Potassium is very important in the water balance of the crop. It affects the uptake of water and the maintenance of turgor in the tissues. Deficiency of K is shown by yellowing and drying of the tips and margins of leaves, particularly at the base of the plant

 Zinc (Zn)

The microelement, zinc, is mostly applied, as it is included in many fertiliser mixtures. A deficiency is characterised by light streaks or bands between the veins from the leaf base to the tip. Under cool overcast conditions, these symptoms suddenly appear but disappear just as quickly once the sun appears


2.16    Compound fertilizers

In Zimbabwe fertilizer application is region specific and mostly in the form of compound blends. For maize Compound D or “maize fert” as is now commonly called is used. It has an NPK content of 7:14:7. There is a new blend commonly referred to as “Double D” with double the elements (14:28:14). This has a transportation advantage. Recommendations made in the table below are based on basal fertilisers with NPK content 7:14:7. Actual rates can be obtained after soil analysis. Basal fertilizers should be applied at planting so that roots can fully utilize the fertilizer at early growth. Fertilizer is banded into the planting station and covered lightly with soil to prohibit seed fertilizer contact. Seed is then dropped into the planting station and then fully covered by soil.

Table 4. Compound fertilizer recommended application rates

Region 1

Region 2

Region 3

Region 4

Compound/maize fertilizer (kg/ha)

300 to 350

(6-7 bags

Compound/maize fertilizer (kg/ha)

300 to 350

(6-7 bags)

Compound/maize fertilizer (kg/ha)

200 to 300

(4-6 bags)


Compound/maize fertilizer (kg/ha)


(3-4 bags)


2.17    Top dressing

Top dressing fertilizer can be applied at once at 5-6 weeks after emergence or split applied by applying half of the quantities at 4-6 weeks and the other half at 7-8 weeks. Top dressing fertilizer is applied approximately 5cm away from the crop to avoid fertilizer burns on the crop. Top dressing should be applied when the soil is moist or when light rains or irrigation follows application.





Table 5. Ammonium nitrate/top dressing recommended application rates

Region 1

Region 2

Region 3

Region 4

Ammonium nitrate (AN)/top dressing (kg/ha)

250 to 300

(5-6 bags)

Ammonium nitrate (AN)/top dressing (kg/ha)

250 to 300

(5-6 bags)

Ammonium nitrate (AN)/ top dressing (kg/ha)

150 to 200

(3-4 bags)


Ammonium nitrate (AN) top dressing (kg/ha)


(2-3 bags)

Other soil nutrient replenishing methods to supplement inorganic fertilizers:

  • Use of cattle manure, cured in pits or heaped.
  • Rotation mainly with grain legumes such as groundnut, Bambara groundnut (Nyimo /indhlubu) and soyabean.
  • Maize intercropping with legumes such as cowpea (Nyemba / indumba)
  • Green manuring using legumes such as velvet bean and sun hemp
  • Use of agro forestry species such as e.g. Sesbaniasesban for improving fallows before planting maize.
  • Use of termitaria  (termite mound) soils


2.18    Fertilizers Application Methods

a)      Drilling using seed drills or planters.

b)      Broadcasting using vicon spreaders or manually by hand

c)      Banding by hand


2.19    Factors having a negative effect on a good crop stand

There are many factors which may affect farmers to achieving a good and even crop stand. These include:

  • Poor soil texture and structure may result in capping hence crop emergence will be retarded.
  • Poor final soil tilth. Leaving land with so many clods will affect crop emergence. The land should have a fine tilth and it should be even.
  • Using poor quality of seed used. Seed sourced from none reputable sources or retained seed have poor germination potential hence the crop stand will be affected.
  • Poor planting methods which leaves planted seed in poor contact with the soil will leave more air spaces in the soil around the seed thereby encouraging fungal disease attack.
  • The efficiency of the planting operation. Seed has to be places at the correct depth. Planting machinery must be correctly calibrated to achieve a good crop stand;
  • Poor weed, pest and disease management practices result in reduced crop stand.


2.20    Maturity

Maize maturity is classified as early (short-season varieties), medium (medium season varieties) or late (long season varieties) If the farm work load normally prevents harvesting early- to medium-maturing hybrids within 30 days after physiological maturity (black layer), consider planting a later-maturing hybrid, which normally has better shuck coverage.

  •  Long season varieties are normally planted late October to beginning of November with supplementary irrigation. The varieties have an optimum yield of 10-15t/ha and are mostly suited for Natural Region 2A and 2B.
  • Medium season varieties. These varieties have an optimum yield of 8-10t/ha. The varieties are mostly suitable for Natural Region 3 where the amount and reliability of rainfall within the season tends to be lower and more erratic.
  • Short season varieties. It is important to understand the difference between short season and drought resistant varieties. Though most drought resistant varieties are short season there are some short season varieties which are not drought resistant. Drought tolerant varieties are mostly suitable for Natural Region 4 where soils and rainfall are generally marginal for crop production. These varieties have an optimum yield of 6-8t/ha. Other varieties can be grown with supplementary irrigation. Short season varieties can be grown in high rainfall areas after removing an early crop e.g. after harvesting irrigated tobacco end of December or by mid- January

• Grain quality and disease and insect resistance

Current hybrids in the market are being bred against major diseases affecting maize in Zimbabwe. However if maize is planted after maize in the same land, the maize is susceptible to leaf diseases due to the build-up of spores. Disease resistance is thus a necessary component of hybrid selection. Grain quality depends on shuck coverage to retard moisture and inhibit insect penetration into the ear and grain hardness.

Recommendations on hybrid selection can be made on the basis of knowledge of the natural regions and the relative performances of the hybrids in these regions.


2.21    Grain yield

Different maize varieties have different yields. Yields will also depend on management practices such variety selection, weed control, disease and pest management. Average yield range is 4-7 t/ha. Some varieties have optimum yields of 10-15t/ha.


CHAPTER 3:                      WEED AND PEST MANAGEMENT


3.1      Weed management

Weeds are unwanted plants that have a negative effect on crop growth. Weeds have many negative effects such as, competing for nutrients, sunlight, moisture, harbouring pests and diseases. Weeds may be controlled using mechanical, biological and cultural methods. Effective control is usually obtained where an integration of all these methods is used.


3.2      Weed control methods

3.2.1   Manual method (Hand)

This involves direct labour or energy from the farmer using hand hoe or hand pulling of weeds. Weeds are pulled out using hands. It works where the weeds are isolated and in moist conditions. Hand hoeing is widely practiced in Zimbabwe. Even where herbicides or tractor drawn cultivators are used, hand hoeing is usually necessary to remove all those weeds found between plants in the row and all these weeds which would have been missed by the other methods.

3.2.2   Mechanical weed control

This method involves use of tractor, ox-drawn machinery (cultivators) to remove weeds between rows. Shallow cultivation using cultivators can be done when the crop is about 10cm to minimise crop damage.

3.2.3   Cultural control

This includes any husbandry or crop management practices that enhance a crop’s ability to out-compete weeds. Methods involved include, species selection, crop spacing and canopy manipulation, mulching, timing of planting, soil amendments and crop rotations.

3.2.4   Chemical control

It involves the use of herbicides. Herbicides should be used where:

  • A suitable chemical is available for the anticipated weed pattern
  • The probable rainfall pattern is such that mechanical cultivation could prove ineffective and the herbicide to be used can work efficiently
  • The yield potential is sufficient to cover the cost of the chemical (while taking into account soil compatibility and labour availability)


Table: 6 Herbicides used in Maize production

Active ingredient

Trade name


Application details           

Application rate



Pre- and early post emergent

Controls broadleaf weeds and some grasses

3-5 litres/ha


Dual Magnum


Controls most broadleaf weeds and nutsedge

2-3 litres/ha



Post emergence

Control B/L weeds & some sedge. Apply from first 3 leaf stage. Use higher rate for sedges & add water.



Nicosulfron 4SC


Controls Shamva and some broadleaf weeds. Add 0.1% Sanawett. Spray before 7 leaf stage of crop.

0.8-1 litre/ha




An early post-emergent herbicide for the control of various broad-leaf weeds.

1.5-2 litres/ha




A non-selective foliar applied herbicide. Active on annual and perennial weeds.

4-5 litres/ha




Control most broadleaf weeds. Direct spray when crop is 7 leaf stage.

0.5-1 litre/ha


3.3      Pests Management


Table 7:          Pests and their control




Maize Stalk Borer (Busseolafusca)



  • Most important pest affecting maize.
  • Attack by the larvae on young plants may permanently stunt the crop and prevent them bearing a cob.
  • The tunneling activities of the more mature caterpillars in the main stem weaken the plants which may then lodge.
  •  Mature cobs are ruined directly by feeding on the grain and indirectly as a result of fungal damage and discoloration.
  • Maize plants of 0.3-1.0m in height are susceptible to attack by the first generation of caterpillars.
  • Characteristic feeding marks horizontal rows of holes on the leaves emerging from the funnel of the plant and frass (droppings) are the first signs of infestation.
  • In the older plants, dirty white caterpillars can be found tunnelling in the stems with frass protruding from the holes and the terminal portion of the stem bearing the tassel may collapse or break off.


  • Carbaryl 5 Dust, Carbaryl 85 WP
  • Dipterex 2.5 Gran
  • Thionex 35 EC
  • Deep ploughing and destruction of stover is the best method of destroying overwintering larvae.



Cutworms (Agrotisspp.)



  • These are sporadic, occasionally devastating pests affecting young maize.
  • They eat the plants soon after germination at ground level and in some cases, may reduce the stand considerably as they attack successive plants in the row.
  • They are greasy-looking, greyish caterpillars. They tend to curl into a 'C' -shape when disturbed, but must not be confused with subterranean white-grubs which are chafer beetle larvae.
  •  Cutworms require green plant material for feeding particularly during the early larval stages.


  • Lands should be left fallow and strictly weed-free for about 6 weeks prior to planting.
  • To ensure mature and most harmful cutworms would not be present when the crop is in the most susceptible stage.
  • Karate at 0.1 litres/ha

African Armyworm (Spodopteraexempta)



  • These are leaf-eating caterpillars which feed on members of the grass family.
  • Notorious for their sudden outbreaks of varying intensity every few years when large numbers of moths migrate into the country.
  • Warnings of imminent outbreaks are broadcast and published by the Plant Protection Research Institute and AGRITEX departments of the Ministry of Agriculture, Mechanization and Irrigation Development.
  • Light and pheromone traps, as well as regular inspections in December and January are used for early detection of out breaks.
  • At first, large numbers of minute green caterpillars can be seen feeding on the leaves. When fully grown (up to 35mm long), the armyworms are velvet--black with fine yellow lines down the body and they eat voraciously, often leaving only stems and mid-ribs of leaves.

They can be controlled by a wide range of contact insecticides and may even be prevented from 'marching' onto a land by applying a band spray along the edge of the field.

  • Carbaryl 85 WP
  • Malathion Dust
  • Malathion 50 EC


Leaf Hoppers (Cicadulinaspp.)



  • These small, mobile sap-suckers are the vectors of maize streak virus. They are about 3mm long, pale yellow and wedge-shaped.
  •  Eggs are laid singly in slits in leaf tissue and hatch into nymphs in about three weeks.
  •  As the veld grasses dry out at the end of the rainy season, the leaf hoppers invade irrigated crops from March to September.
  • The hopers are vectors of streak viruses.


  • Clear barriers of 10 - 20m
  •  Plant upwind from infested areas.
  •  Avoid too early planting.
  •  Do not plant an irrigated maize crop close to a summer crop not yet harvested. 
  • Granular soil treatments, seed dressings or systemic sprays.
  • Plant maize cultivars the maize streak and maize mottle/Chlorotic stunt viruses
  • Streak-infected plants should he pulled out after spraying to prevent spread of the disease.

 Chemical control:

  • Oncol 20 EC
  • Curater 10 G, Carbofuran10 G
  • Gaucho 70 WP
  • Rogor CE, Dimethoate 40 EC

Termites (various spp.)



Termites are liable to attack the standing crop throughout the season, but damage is particularly noticeable during periods of drought and in areas of unreliable rainfall. The base of the stem and buttress roots are attacked, resulting in lodging. Once fallen, the cob itself is eaten and harvesting becomes difficult. The damage varies according to the species involved and control measures need to take this into account.


  • Termites attack crops both in the field and in storage.  Control of termites varies between these two environments.
  • When termite attack is high, it is advisable to harvest the crop early and reduce extend of crop damage
  • Good cultural practices ensure a healthy crop which has a better termite resistance than a poor and stressed crop
  • Termites can also be controlled through destruction of the mounds




3.4      Diseases Control


Table 8:Diseases and their control




Root and stalk rots(Pythium, Fusarriumstalk rot)



Caused by several different fungi, these diseases can result in corn lodging and inferior ears from lodged plants on the ground and premature ripening on diseased stalks. Stalk rots typically result in greater damage in poorly drained soils and when drying conditions are slow due to poor air movement. The soil-borne fungus Fusarrium stalk rot normally begins soon after pollination and becomes more severe as plants mature. Symptoms include whitish-pink discoloration of the pith, stalk breakage, and premature ripening.


Control practices include good cultural practices such as planting recommended varieties which are resistance to lodging, using early maturing varieties where lodging is severe and avoiding poorly drained fields.

Do not irrigate in hot, sunny conditions


Leaf blights



Caused by different species of the fungus (Helminthospo­rium). These diseases favour wet or humid field conditions. Symptoms are lesions that are tan, oval to circular and usually with concentric zones. The fungus also attacks ears causing a black, felty-mold over kernels. Tolerance among maize varieties can vary.


Plant recommended resistant or tolerant varieties.

use of rotations


Ear and kernel rots





Some of the fungi that cause silk rots or leaf blights may also infect the ear. Symptoms including; a pink, powdery mold growing over the surface of rotted grains (Fusarium) and dense to white mold growing between the rows of rotted kernels (Diplodia).


  • Some protection can be obtained by planting varieties resistant to ear-feeding insects and lodging. Some hybrids may offer slight resis­tance or tolerance. Early harvest at physiological maturity and proper storage are helpful

Maize Streak virus


40% Dimethoate at 50ml per hectare.

Boil smut


Standard seed dressing eradicates the seed borne infection

Maize rust


Breeding for resistance

Grey leaf spot


Breeding for resistance. Use score (fungicide) at 0.25 litres per hectare,

Apply in mixture with Bavistin  (300g/ha) at 14-21 days intervals.



3.5      Storage Pests

Primary storage pests such as Grain borers, Weevils and Angoumois grain moths are able to feed on whole grains. Secondary pests such as flour beetles can attack only broken grain or moist and soft grain.

Table 9. Storage pests and control



Weevils (Sitophilusspp)


The insect attacks grain both in the field and storage. The adult weevil bores some holes into the grain and lays eggs inside. The eggs hatches into larvae and begins to feed on the grain from the inside. Taints of white and dusty excreta produced by the larva are seen on grain surfaces. Respiration of the insect during high infestations results in heating which is followed by moulding and caking of grain in storage.


The Larger Grain Borer (LGB).(Prostephanustrancatus



The LGB is a pest of economic importance in maize. It causes losses of up to 34% within a period of six months. When compared to its counterpart beetles i.e. the lesser grain borer, it is larger in size, 3-5mm long and more cylindrical in shape. When viewed from the top it gives an impression of a square. Attack of grain by the LGB starts in the field and is severe in storage. The insect pest bore neat round holes on grain and produce a lot of flour.




The Lesser grain borer (Rhizopetha Dominica)



The lesser grain borer attacks cereal grains and products like the LGB. It almost looks the same as the larger grain borer, except that it is smaller in size. The head is much smaller and the back is concave in shape when viewed from above. Both the larva and the adult bore round tunnels up to 1mm diameter into the grain. Grains are hollowed out at the later stages of infestation.



3.6      Control of storage pests

  • Early harvesting (at physiological maturity if pest infestation is high)
  • Cleaning grain by removing pest infested grain before storage.
  • Treat grain with synthetic insecticides before storage.


3.7      Grain treatment method

  • Clean the storage structure and burn sweepings.
  • Clean the grain to remove all residual pests.
  • Select a suitable insecticide.
  • Carefully read the instructions on the label noting the application rate and safety precautions.
  • Dust the inside of the store (walls and floor.)
  • Treat only one or two bags (50kg) at a time.
  • Measure out the correct dose of chemical for the number of bags to be treated.
  • Sprinkle the dose of the chemical on the grain and mix thoroughly. To obtain even distribution, mix the required amount of insecticide with small amount of grain (one bucket) and then with the rest.


Table 10: Insecticides for grain treatment

Trade name

Active ingredient

Application rate

Shumba super

Deltamethrin, fenitrothion

Mix 25g per 50kg bag of grain


Piriphos-methyl, Deltamethrin

Mix 20g per 50kg bag of grain

Actellic super


Mix 25g per 50kg of grain

Chirindamatura dust


Mix 25g per 50kg of grain

Shumba 2 dust


Mix 18g per 91kg bag

Grain guard 3 dust


45g per 90kg bag of grain 





4.1      Timing for harvesting

When field losses are high, harvesting can be done when the crop reaches physiological maturity. At this point the kennels would be having high moisture content of between (35-40 %). Such moisture levels do not allow storage of the grain. Further out of field drying is recommended. Contrary, when field losses are low the crop should be allowed to dry in the field for 2-4 weeks and then harvested. This allows time for the crop to dry to safe moisture content (20-25%) for harvesting.

When the crop is mature it begins to develop the following physiological maturity characteristics.

  • Yellowing and drying up of most of the leaves and husks turning papery.
  • Maize grains acquire a glossy surface.
  • The grain is too hard and uncomfortable to chew when it is roasted.
  • Maize cobs begin to hang downwards on the stalk, (drooping).
  • The silk completely dries up and turns black in colour.


4.2      Harvesting methods

Harvesting of maize is a process whereby the cobs are removed from the stalks. Maize can be harvested manually by hand and mechanically by combine harvesters.


4.2.1   Manual harvesting

Maize cobs can be removed from stalks with or without husks depending on their intended use.  Dehusked cobs are mainly used for human consumption whilst husked cobs can be used for production of stock feeds. There are two main methods that are used in harvesting maize manually. These include, dehusking the crop on the stand (direct dehusking) and dehusking the crop after drying on stacks or windrows.


4.2.2   Direct Dehusking

The cobs are dehusked directly from the standing stalk and put straight into containers to avoid shattering. Sometimes the cobs can be heaped and then later loaded into a carrier- container, bag, and wheel barrow or scotch cart. If the field is near the homestead and the quantity of maize is small, the crop can be transported home using containers or bags. This method is highly practiced in Conservation Agriculture as it allows even distribution of stover in the field. Direct dehusking saves on labour and time required to cut the maize stalks and gather them together into stacks or windrows.


4.2.3   Dehusking on Stacks or Windrows

The maize crop is cut and gathered together in stacks or windrows. The cobs will be left to dry for a period of one to two weeks after which the maize cobs will be dehusked from the stalks. This method reduces loss due to cobs left on both standing and fallen stalks as compared to direct dehusking. It also reduces fatigue and drudgery because it ensures one operation at a time. Piling is done on an open space which reduces scattering and left-overs upon loading into carriers. However care needs to be practised to avoid shattering.

Losses of maize are encountered in this method through:

  • Restricted air movements which may lead to development of fungi and insects.
  • Slow drying rate and repeated wetting from late rains may lead to formation of moulds.
  • Termite attack on the maize plant in contact with the ground.


4.3      Management Practices to Minimize Losses

  • Use varieties that are resistant/tolerant to crop lodging, pest and disease attack at physiological maturity.
  • Application of proper crop production management practices. Healthy crops are tolerant to pest and disease attacks.
  • Stacked crops should not be compressed to allow free air circulation.
  • Dehusking should be done at optimum harvesting time to reduce exposure to agents of post-production losses in the field.
  • Cobs should not come into contact with the ground to avoid termite attack, cob rots and or soiling.
  • Pick up all scattered cobs and heap them together before loading.
  • Separate damaged and or diseased cobs from the normal ones to avoid pest attack, cross-contamination of fungal diseases (moulds).


4.4      Combine Harvesting

Combine harvesting should be done when maize grain moisture content is such that grain will not be damaged during the harvesting operations. Harvesters that take the whole plant through the drum cannot work on dump plants. Combine harvesters will not pick up cobs lying on the ground and will not work efficiently on badly lodged crops. Dense weed infestations can cause blockages. However mechanical harvesters can reap fast.


4.5      Storage

An ideal storage facility should ensure that grain does not deteriorate both in quality and quantity. The most important storage requirement is to protect grain from agents of deterioration namely temperature, moisture and pests (including rodents and insects). The grain should be cool, dry, clean, undamaged, free from initial insect infestation and healthy in order to maintain its quality

Extraneous matter harbours pests and reduces exposure of grain to chemical protectants; therefore it is necessary to make sure the grain is cleaned before being put into stores.


4.6      Marketing

Maize can be marketed anywhere in Zimbabwe. Farmers may trade with whoever they wish; therefore various marketing options are available through:

  • GMB (Grain Marketing Board)
  • Millers
  • Stock feed producers
  • Private traders
  • Farmer to farmer

The grain marketing board offers a number of services in addition to being a major buyer. These include grading, weighing, moisture testing and contract storage.


4.7      Exports and imports

Currently maize cannot be exported outside of Zimbabwe. Imports of maize are done after obtaining an import permit from the Ministry of Agriculture Mechanization and Irrigation Development.



Target Yield (T/Ha)






Blend Selling Price ($/T)


 $     350

 $     350

 $     350

 $     350



 $  1,050

 $  1,400

 $  1,750

 $  2,100

Total Variable Costs (Tvc)


 $  1,122

 $  1,311

 $  1,428

 $  1,545

Gross Margin (Gm)


-$       72

 $        90

 $     322

 $     555

Gross Margin (Gm)/$100tvc


-$         7

 $          7

 $        23

 $        36








Unit cost





1. Labour:


 $        42

 $        42

 $        42

 $        42

2. Tractor and Equipment:


 $     218

 $     218

 $     218

 $     218

3. Seed: kg - Short


 $        60

 $        60

 $        60

 $        60

               - Long






4. Fert. amd Lime:






    a. Compd D


 $     162

 $     194

 $     227

 $     227

    b. AN:


 $     130

 $     194

 $     194

 $     227

    c. Agric. Lime: .25t


 $     170

 $     170

 $     170

 $     170

    d. Transport costs:


 $        35

 $        43

 $        45

 $        48

5. Herbicides:






   a. Alachlor 43EC:


 $        14

 $        14

 $        14

 $        14

   b. Dual


 $        20

 $        20

 $        20

 $        20

   c. Gramoxone


 $        12

 $        12

 $        12

 $        12

6. Insecticide:






Endosulfan 35MO: 1.32 L


 $        12

 $        12

 $        12

 $        12

7. Insurance:


 $          6

 $          8

 $        10

 $        12



 $     880

 $     987

 $  1,024

 $  1,060

Harvesting And Marketing






1. Labour


 $        41

 $        55

 $        69

 $        82

2. Tractor and Equipment:


 $        19

 $        26

 $        32

 $        39

4. Packaging






   a. Bags


 $        30

 $        40

 $        50

 $        60

   b. T2 Twine:






5. Transport off farm:


 $     150

 $     200

 $     250

 $     300



 $     242

 $     324

 $     404

 $     485



 $  1,122

 $  1,311

 $  1,428

 $  1,545



 $     374

 $     328

 $     286

 $     258

 Fert. requirements in tonnes






    a. Compd D:






    b. AN:






    c. Agric. Lime:






    d. Transport costs:







  • Giga D. P. and Katerere, Y (1986).Rural Grain Storage in Zimbabwe: Problems loss assessment, and prevention. University of Zimbabwe: ENDA Zimbabwe
  • Odogola W.R. and Henriksson R (1991). Technical systems for agriculture: postharvest management and storage of maize. AGROTEC UNDPS/OPS Regional Programme
  • Nukenine E. N (2010). Stored product protection in Africa: Past present and future. Dept of Biological Sciences: University of Ngaoundere, Cameroon, Julius-Archiv 425.
  • Grain production handbook