The Sunday Mail
Wendy Madzura
Agriculture in Zimbabwe contributes 15 to 18 percent Gross Domestic Product (GDP), with over 70 percent of households dependent on it for their livelihoods.
It is, therefore, prudent that farmers are conscientised on the concept of increasing productivity at farm or household level.
This will have a net positive effect on increasing productivity and production at national level. Once Zimbabwe attains food security at national level, we will be able to export the surplus and obtain the much-needed foreign currency to revive our industries and grow our economy (ripple effect).
The onset of the rains has seen farmers striving to establish their rainfed summer crops and get some reprieve on irrigation for the earlier planted crops, especially maize, the staple food crop of Zimbabwe.
Other major food crops that farmers are growing include groundnuts, sugar beans and small grains like sorghum, millet and cowpeas.
Farmers are also growing cash crops like tobacco, soya beans and cotton.
Planting time is one of the key factors to increasing productivity at farm and national level, with yield loss above 100 to 120kg per hectare per each delayed week after November. Timely crop establishment promotes adequate use of resources such as the length and amount of rainfall in line with the seasonal forecast.
Heat units are also a key ingredient in the rate of growth of crops, especially maize, with 40 percent of the heat units being received within the first three months of the cropping season (October, November and December).
It is imperative to establish crops early and optimise on the yields.
Profitable farming operations are hinged on the ability to select climate-smart varieties that can withstand long periods of drought in the wake of climate change.
It should be coupled with the adoption of Good Agronomic Practices (GAP’S), which include variety selection.
Factors that influence variety selection include:
Expected season quality — the length and amount of rainfall expected in a season;
the altitude of a given area ;
the desired plant population in relation to the yield target;
the fertility programme; and
the general crop management
The SADC region experienced the El Nino phenomenon in 2018/19 season, which resulted in a shift of rainfall patterns.
Farmers are encouraged to grow “climate-smart” varieties from different maturity groups to mitigate risks of crop failure or drought.
Seed Co, the pan-African seed company which has stood the test of time, has, through 80 years of research, continued to evolve in a bid to embrace new innovations and technologies that have resulted in improved, more adapted and climate-smart genetics.
Product basket
The Seed Co product basket consists of a wide array of crops from maize, sorghum, soyabean, sugar beans and wheat.
Seed Co has also embraced horticulture seed production in a bid to ensure that farmers get high-yielding, quality-guaranteed products that will add value to their farming enterprises’ “creation of a one-stop shop”.
In the maize category and in light of climate change, Seed Co has embarked on different climate-smart mitigation measures which include: ultra-early (short season) maturity varieties (SC 301), adaptation to drought (tolerance) inclusive of the medium- and late-maturity varieties which have been termed “hard-body varieties”, varieties that are adapted to high temperatures and heat stress, varieties with a high nitrogen use efficiency to manage leaching which result from the heavy downpours.
The varieties have good disease tolerance and resistance, especially to cob rots.
Seed Co breeds varieties suitable for every farmer.
Maize hybrid varieties
The ultra-early maturity variety SC 301 is the earliest maturing hybrid on the market, taking between 90-120 days to reach maturity. This variety fits well in low rainfall areas characteristic of Natural Region Four and Five.
It is also a best suit for late planting as well as for multiple cropping programmes in one season.
In the 400 category, we have the early maturity variety SC 403.
It is known for its stability across environments and early maturity period, which ranges from 115 to 127 days. This variety is a good fit in Natural Regions Four and Five, where the length of the growing season is not long, having an average rainfall volume of 450mm-650 mm.
In the 500 series category is one of the most widely grown maize variety, SC 513. This variety is known for its consistent performance across environments. It matures in 127-137 days and has a yield potential of nine to 10 tonnes per hectare.
However, in this maturity group is one of the new Seed Co flagships — SC 529 — a high-yielding improved hybrid with the ability to yield up to one tonne per hectare. SC 529 has long attractive cobs and excellent tip cover, which curbs against cob rots that can result from late rains.
In the 600 series group are medium-maturity hybrids from the well-known SC 627, 637 to Seed Co’s new flag ship, SC 649. SC 649 has been termed “desert walker” because of its ability to withstand long periods of moisture stress, especially during the vegetative stage. This variety is the highest yielding in its maturity group, with a yield potential of 14 to 16 tonnes per hectare.
SC 649 is good for silage because of its stay-green gene, which enables it to have a longer sillage-cutting window. SC 649 variety is bulky and leafy, allowing for a good grain-to-chaff ratio, which is a key component for sillage.
To top it all up, Seed Co has the highest yielding maize hybrid not just in Zimbabwe but in Africa. The late maturity hybrids SC 727 and SC 719 have yield potentials that emanate from the three-yield components.
These are high row number 18 to 20, high shelling out percentage (over 80 percent) and long attractive cobs. These varieties are best-suited for Region One and Two under rain-fed conditions or under irrigation.
Under rain-fed conditions farmers are encouraged to establish these long season varieties early to optimise on the length of the season.
At planting, farmers are encouraged to embrace advice from Seed Co and Government agronomists/extension staff in their areas so that they “start right”.
It is important for farmers to take cognisance of planting tips that increase chances of obtaining an even crop.
Plant population is important in increasing productivity because yield is a function of two things — yield per plant and yield per unit area.
To achieve optimum plant populations, farmers are encouraged to plant at recommended plant spacing that is aligned to the variety, region and cropping plan.
In low-rainfall areas like Region Four and for farmers with no irrigation, populations of 37 000 to 44 000 plants per hectare are encouraged.
This will reduce competition amongst plants for sunlight, water and nutrients, which may result in low yields.
However, irrigated crops in those regions can benefit from higher plant densities.
In high potential areas — Region One and Two or under irrigation — farmers can increase their plant population to optimum levels depending on the variety.
The optimum plant population recommended for Seed Co varieties is 50 000 to 60 000 plants per hectare.
Farmers are encouraged to do a cost-benefit analysis of the input costs and additional costs for growth regulants versus the yield that they obtain to avoid reduction of profit margins.
As a guide, farmers can plant at an inter-row spacing of 75cm-90cm and in-row spacing of 20cm – 25cm.
In some cases, in-row spacing may reach 40cm when farmers are planting two peeps per station.
Planting depth is an important factor which affects crop stand or plant population.
It is important for farmers to consider the size of the seed, soil conditions and seasonal forecast when selecting the planting depth.
Farmers are encouraged to cover the seed with a layer of soil that is twice the size of the seed as this promotes good germination and crop establishment.
In maize, the planting depth can be in the range of 4cm to 6cm, and deeper planting is encouraged for sandy soils or when dry planting.
Fertilisers and Chemicals
Basal fertiliser application is a key ingredient in increasing yield, provided the nutrient requirements of the crop are met.
Framers should know that basal fertiliser is important in the establishment stages of the crop for root development and it must be applied before or during planting.
Caution must be taken to avoid direct contact of the fertiliser and seed as this may result in the destruction of the seed.
In a bid to attain sustainable agriculture (Green Revolution), farmers are encouraged to incorporate organic matter or manure in their cropping programmes to enrich the soil, improve drainage and soil structure.
The manure should be fully decomposed to minimise introduction of diseases or insect pests.
Regular scouting is pivotal in insect pest and disease control as they can be managed before they reach threshold levels that may result in economic yield losses.
Variety selection can also reduce the cost of disease management through the selection of disease-tolerant and resistant varieties like the Grey Leaf Spot GLS, cob diseases and leaf blights.
Seed Co has factored in varying degrees of resistance and tolerance to these diseases that have the potential to reduce yields.
During planting, farmers should make sure that the seedbed is weed-free, especially for the first 10-12 weeks of a maize crop cycle, as this is the period when more than 60 percent of the available nutrients are used or required by the crop.
Generally, failure to control weeds during the first five weeks of the crop cycle leads to a 50 percent yield reduction. When using herbicides farmers are encouraged to take into account the weed spectrum, future cropping plans and time of application for effective and efficient use of herbicides.
A good example is when using pre-emergence herbicides. It is important to note that the pre-emergence herbicides should be applied on moist soil to control weed seeds.
Contact agro-chemical companies for more information on the effective use of herbicides.
In view of climate change, farmers are encouraged to embrace water harvesting techniques that will enable them to conserve moisture for long periods and sustain their crops during periods of dry spells.
Farmers can use water or moisture conservation techniques like pot-holing, tied ridges, wet ripping and mulching to reduce the rate at which moisture is lost.
Time waits for no one, hence farmers are encouraged to plant their crops early to increase chances of obtaining high yields.
Farmers should always remember that there are a thousand reasons for low yield, but only two reasons for high yields — variety selection and good agronomic practices (GAP’s).
Wendy Madzura is an agronomist with a Zimbabwe Stock Exchange-listed company that breeds, produces, processes and markets hybrid crop seeds.
