Agriculture in Zimbabwe contributes 15 to 18 percent of the Gross Domestic Product (GDP), with over 70 percent of households dependent on it for their livelihoods (Mhlanga, 2018).
It is therefore prudent that farmers be educated on the concept of increasing productivity at farm or household level. This can be achieved through embracing the “climate proofed” productivity enhancement initiatives that are part of the Agriculture recovery plan spear-headed by the Ministry of Lands, Agriculture and Rural Resettlement in Zimbabwe.
Conservation agriculture in its broad sense falls under this plan and will help mitigate against the effects of climate change. Conservation agriculture techniques for commercial/resource endowed farmers involves the use of specialised implements which include no-till planters while the resource constrained communal/small scale farmers are implored on to embrace the “Pfumvudza/Intwasa” concept.
This will have a net positive effect on increasing productivity at the grassroots and 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 thereby creating a positive ripple effect resulting in food self-sufficiency, improved nutrition and profitability.
Agriculture in Zimbabwe is hinged upon three main pillars, Access to Genetics, Access to Finance, and Access to Extension and Agronomy services to unlock the genetic potential of crops. In effect, there are a thousand reasons for low yields but only two for high yields which are: Selecting the best germ-plasm or seed for a given crop and Employing Good Agronomic practices (GAP’s).
The selection of the best germ-plasm is guided by the knowledge of a wide range of factors as well as the desired crop and variety traits and crop management (Good Agronomic Practices) that will unlock the genetic potential of the established crop (maximum attainable yield). Increasing crop productivity is best achieved by understanding the following five factors:
Seed factor (Right Seed)
(a). Yield potential, (b). Drought escape/ tolerance (c). Disease tolerance (d). Crop Standability
Climatic factors (Abiotic/ non-living factors)
Altitude and air temperature (b). Rainfall amount and distribution (seasonal forecast)
Planting dates and (b). Irrigation scheduling (c). Scouting and effective pest management (d). Rotation plan
Soil (biotic & abiotic) factors
Soil fertility (b). Soil pH (c). Soil structure
Biotic factors (living)
Diseases (b). Insects (c). Weeds
Selecting the right seed is hinged on a farmer’s desired outcome and knowledge of the end use of the produce. Some farmers may want to produce for silage, green mealie or grain and variety choice should be guided as such.
Maize which is the staple crop, traditional grains, legumes and vegetables are amongst the crops that farmers can produce during the rainy season. However, farmers should be conscious of the fact that disease and insect pressure tends to be high during the rainy season as a result, farmers should prepare accordingly to avoid incurring economic yield losses.
Farmers are implored to embrace the “climate smart”, modern innovative seed technologies which are aimed at mitigating against the effects of climate change. In maize production these include ultra-early maturing maize varieties like SC 301 (90-120 days to reach physiological maturity), drought tolerant maize varieties like the very early maturing SC 419 and early maturing SC 529 and SC 555, medium maturing SC 649, 657, SC 659 and the late maturing SC 719 and SC 727.
In addition to this, farmers are encouraged to be health conscious and adopt bio-fortified crops. These include the bio-fortified orange maize, ZS 242 with vitamin A.
The choice of crop or variety to grow should always be guided by market analysis and seasonal suitability. Crop and variety choice is the cornerstone to profitable farming hence farmers should seek advice from agronomists.
Climatic factors such as humidity, cloud cover, wind, altitude, air temperature and the rainfall pattern are important elements in farming because they act as the enablers for the crop to grow.
Crops established in areas of high altitude tend to take a longer time to reach physiological maturity due to the cool weather conditions associated with the low heat units while crops established in areas of low altitude tend to grow much faster because of the higher heat units experienced.
The rainfall amount and distribution is an important yield determinant especially under rain fed agriculture. Farmers should always align their cropping plans with the nature of the season to enable informed crop and variety choices to be made.
The 2020/21 cropping season has been said to have a normal to above normal rainfall pattern for most parts of the country. The onset of the rains has brought with it hope and prospects of a productive season.
As the 2020-21 farming season progresses, farmers should never under estimate the secret ingredient in farming (a farmers’ foot print) in the field. This is one of the most important management aspects of any profitable farming venture). Timeliness of farm operations such as planting dates (irrigated or dryland crops) and fertiliser application type, time and rates (basal versus top dressing) are all hinged on the farmers level of commitment to the farming enterprise.
During planting, farmers are encouraged to use the recommended seed rates and spacing to achieve the optimum plant population for a given crop and variety. This is because yield is a function of two things, yield per plant and yield per unit area.
For maize, farmers can use 25kg’s of seed to plant 1hectare (2,5acres) or seed packs that come with specified number of kernels (20 000 kernels or 50 000 kernels).
The recommended inter-row spacing for maize is 75cm to 90cm while the in-row spacing is 18 to 25cm. Farmers should aim to achieve a plant population of 50 000 to 60 000 plants per hectare in high potential areas or under irrigation while low rainfall potential areas are recommended to achieve a plant population of 36 000 to 44 000 plants per hectare. If germination is poor, gap filling or re planting should be done in the 1st two weeks after crop emergence.
The soil is the main growing media in which crops grow and as such, is a key ingredient in increasing crop productivity. Soil pH, fertility status and structure determine the crop’s ability to utilise available nutrients to achieve an intended yield level. The pH level describes the soils acidity or alkalinity on a calcium chloride scale or potassium chloride scale. In Zimbabwe 70 percent of the soils are acidic and as a result farmers are not reaping the full benefits of organic or inorganic fertiliser applications because acidic soils reduce availability of macro and micro-nutrients for crop growth thereby reducing the fertiliser use efficiency.
The best way to address soil pH and understand the nutrient requirements of crops is through soil analysis. Basal fertiliser should be applied before or at planting in the form of compounds or specialised blends depending on the crop. For maize farmers can use compound D with a Nitrogen: Phosphorous: Potassium (N:P:K) ratio of 7:14:7 or blends (6:23;23 or 14:28:14. For top dressing fertilisers, (AN or Urea) should be applied at the vegetative stage of a crop to promote vigorous growth which ultimately gives high yields. Split application is encouraged for top dressing fertilisers to reduce leaching and volatilisation of AN and Urea respectively.
The soil structure affects root growth, water infiltration and beneficial microbial activity thereby impacting on crop production. Soils with poor drainage (plough pan or heavy clays) tend to reduce water infiltration and promote runoff. Improving the soil structure is one way of ensuring that we preserve the abundant growing media in a way that allows for effective crop growth without compromising the environment for future generations (sustainable agriculture).
The adoption of conservation agriculture is hinged upon three pillars: i) minimum soil disturbance; ii) permanent ground cover ; iii) rotations is one way in which the soil structure and water can be conserved. Farmers are also encouraged to use manure (organic matter) that is fully decomposed to avoid the introduction of insect pests and diseases.
The choice of land preparation should aim to achieve a fine tilth which will ensure good seed to soil contact and effective germination resulting in a healthy crop stand in increased productivity. In addition to this, water harvesting techniques such as pot holing, tied ridges and mulching are greatly encouraged to mitigate against the unforeseen weather vagaries of climate change which include prolonged dry spells and droughts.
Biotic factors are amongst the major yield reducing factors therefore farmers should always be on high alert. Before establishing any crop farmers, should understand the problematic insect pests and diseases that might affect the crop and prepare for them. Some varieties may be resistant or tolerant to problematic diseases like Maize Streak Virus (MSV) and Grey Leaf Spot (GLS) in maize, leaf rust in soya bean and a selection of such varieties may have a cost saving effect thereby increasing profitability in farming.
Effective insect pest control depends on the identification and timeous control of the insect pest. In maize production, problematic insect pests include Fall army worm, African army worm, stalk borer chillo worm. Regular scouting is encouraged to determine insect pest pressure before economic threshold levels are reached for effective control. This is achieved through the rotation of insecticides with different active ingredients and modes of action. It also reduces over application of agrochemicals which can promote the development of insect resistance.
It is also pivotal for farmers to effectively manage weeds using an integrated approach of cultural/ mechanical and chemical methods of weed control. Weeds compete with crops for nutrients, water and growing space resulting in low yields. Weed control for the 1st 10 to 12 weeks after crop emergence is encouraged and maintain a weed free field until harvesting.
Farmers should integrate the above factors to obtain optimum yield levels for increased productivity and profitability. Farming is a business, it starts with the right seed coupled with Good Agronomic Practices (GAP’s).
Wendy Madzura is the head of Agronomy at Seed Co Zimbabwe Ltd.