Feeding your crop properly
You can own all the machinery in the world, but if each planted seed does not receive adequate nutrition to ensure the highest possible yield, you’re on a hiding to nothing. Dr Benard Ngwene, agricultural advisory manager for AGCO Africa, explains how to achieve optimal nutrient levels.
Neglect to apply the required nutrient providing fertiliser in any kind of crop production, and you will have weak growth and yield, as well as heightened susceptibility to pests and disease. The following offers some pointers on how to ensure that your plants absorb enough minerals to thrive.
Lay down the basics
For a good harvest, two categories of plant nutrients, namely macronutrients and micronutrients, are required. The former, which are needed in relatively large amounts, are further divided into primary and secondary groups based on their importance. Nitrogen (N), phosphorus (P) and potassium (K) are some of the main primary nutrients readily available in mineral fertiliser. The most commonly used secondary nutrients are magnesium (Mg), calcium (Ca) and sulphur (S). One of the reasons that smallholder farmers generally fail to achieve the yields obtained by commercial farmers is that they do not have access to these secondary macronutrients.
Micronutrients are required in only small amounts, and are less likely to result in crops displaying deficiencies if they are unavailable in the soil. They include iron (Fe), manganese (Mn), boron (B), copper (Cu), zinc (Zn) and molybdenum (Mb). All of these are absorbed through the roots as dissolved ions in the soil solution. Therefore, soil moisture is a crucial aspect of plant nutrition.
Assess crop requirements for nutrients
Nutrient requirements are influenced mainly by crop type and yield expectation. For example, to obtain a maize yield of about 6t/ha, a farmer will need to apply about 140kg/ ha of N. This can be provided via mineral fertiliser, manure and the soil. The application rate should be based on a soil test, which an agricultural extension officer should be able to facilitate. Soil testing also provides a full analysis of the soil type so that a farmer can manage nutrients optimally. For example, the more sandy the soil, the poorer its retention of water and nutrients; as a result, smaller, more frequent applications of water and fertiliser work best. The analysis will also reveal the soil’s pH level. The ideal pH for most arable soils is between 6 and 7,5. If a land has acidic soil, it can be corrected through liming. This is the application of calcium- and magnesium-rich materials, such as chalk or limestone, which react as a base and neutralise soil acidity. Liming also promotes earthworm activity and the breakdown of organic material.
Soil nutrition products can be supplied in the form of mineral fertiliser and manure.
A farmer should also conduct a soil test to evaluate which nutrients are already available in the soil and in what quantity, and then determine the application rate based on these results.
Get the timing right
Rate, timing and application are all very important in nutrient management. Plants require various nutrient rates and ratios at different growth stages. The optimal timing for fertiliser application is therefore determined by the nutrient uptake pattern of the crop and has a significant effect on yield.
Usually P and K are applied prior to crop establishment as they are less prone to leaching. Nitrogen, on the other hand, should be split into several applications. These vary from one crop to another, and should match the period of optimal crop uptake during each of these stages: planting, the high vegetative growth phase, and flowering.
Liming Promotes The Breakdown Of Organic Material
Legumes, for example, need only small amounts of basal N to boost growth prior to N-fixation. And after a legume crop has been harvested, more soil N is available due to N-fixation by the legume crop. Soil type also affects the timing and frequency of fertiliser application. Most smallholder farmers use the broadcast application method, but this might not be as efficient as banding. Broadcasting refers to the spreading of fertilisers uniformly all over the land. Banding, either in rows or hill placement, ensures that the fertiliser is placed close to where it is needed and where the plant can access the fertiliser. It therefore reduces waste.
To sum up
- If you take care of the nutrition of your soil, the soil will take care of your yield.
- For proper fertiliser management, start with calculating fertiliser application rates according to crop type and yield expectation.
- Get to know the nutrient levels in the soil by performing a soil test, then apply mineral fertiliser and manure accordingly and at the appropriate time to limit waste.
Dr Benard Ngwene
Training Manager, Africa