Soil maintenance for successful agriculture


By Dr Tony Monda

AGRICULTURE in Zimbabwe is the backbone and fulcrum of the economy.  

It is the trigger for sustainable national development and the potential store of our sustenance.  

Given the negative impact of the global COVID-19 pandemic on all sectors of the collective economies, the necessities of success in this cardinal sector of our economy cannot be left to chance, nor can we rely on the bountiful whims of nature.

Thus, the contemporary Zimbabwean farmer must create favourable conditions in the soil and environment to reap maximum agricultural yields.  

With the end of winter soon upon us, the foremost task farmers in Zimbabwe face is to enhance the yielding capability of their soil.

Zimbabwe was divided into five agro-ecological regions (NR), in the 1960s, (Region One to Five) in accordance to differences in effective rainfall.  

Annual rainfall was usually highest in Region One which covered approximately two percent of the land area; a specialised and diversified farming region with plantation forestry, fruit and intensive livestock production. 

Natural Region Two covered 15 percent of the land area and receives lower rainfall than Region One, and is nevertheless suitable for intensive farming based on crops or livestock production.

Natural Region Three, a semi-intensive farming region covered 19 percent of Zimbabwe, with moderate rainfall with severe mid-season dry spells that make it marginal for maize, tobacco and cotton, or for enterprises based on crop production alone.

Natural Region Four is a semi-extensive farming region covering about 38 percent of Zimbabwe. 

Rainfall is low with periodic seasonal droughts and severe dry spells during the rain season are common. 

Crop production is therefore risky except in certain very favourable localities where limited drought resistant crops are grown as a sideline. 

Here farming is based on livestock and drought-resistant fodder crops.

Natural Region Five is an extensive farming region covering about 27 percent of Zimbabwe. 

Rainfall is too low and erratic for reliable crop production of even drought-resistant fodder and grain crops, and farming is based on grazing natural pasture. 

The Natural Region (NR) classification divided the country into the five agro-regions based on annual rainfall.  

Here, soils were rated with the assumption that the productivity of certain soils could be improved if certain economically feasible improvements were made. 

However, with evidence of climate change and variability, the increased variability of rainfall has affected these agro-ecological region boundaries. 

In fact, results of a study show that the number of regions remained the same although the size of the regions have changed. 

The shrinking of Natural Regions Two and Three – the main food producing areas in Zimbabwe, pointed to likely reduction in food production and a threat to food security.

Soil structure is the way in which soil is made up of its different component parts.  

The chemical and physical properties of the soil that are relevant in crop production were used to rate the productivity of the soils. These parameters included the basic soil requirements of major crops grown in Zimbabwe, which are the water holding capacity, soil structure, the nutrient status of the soil and its depth. 

Faced with this knowledge, it is incumbent for farmers to know that, besides rainfall, soil is the most important element/crucible for farming.

As we prepare for the new 2020/2021 farming season in Zimbabwe, it is important for indigenous farmers to know that the soil requires nurturing, reconditioning and rehabilitation in order for the agricultural land to yield the various cash and sustenance crops that buoy our agro-economy.

Our farming and agricultural pursuits must be well-planned and well-timed.

However, in order to achieve and maintain favourable soil conditions, farmers need to protect the soils from silting or dissolution by preserving fertile soils that are part of the ecological 

bio-cycle capable of supporting life.

Soil management is an essential component of farming in which farmers are advised to encourage the bio-synthesis of the soil through means of practising diligent and careful management of this vital natural resource and the environment that contains it.

This practice is known as ‘soil conservation’.

Water retention in the soil has to be balanced with a certain amount of drainage or absorption, depending on the soil type and friability of the land the farmer is farming on.  

Well-textured, fertile soils result in good quality crops and bountiful yields. 

The soils in Zimbabwe are extremely varied; ranging from red soil to greyish brown sands and sandy loams derived from granitic rocks, to deep Kalahari sand to brown loamy sands and loams clays.  

The light, clay sandy and loose soils the most common soil types found in most parts of Zimbabwe, are residual soils developed largely from the granite parent material.  

Many experienced Zimbabwean farmers understand that successful crop farms have been improved over the years by soil conditioning, manuring, fertilising and reconditioning.  

The light and sandy soils found in most parts of Zimbabwe are residual soils developed largely from the granite parent material.

Prior to embarking on an agricultural project, new farmers in Zimbabwe need to first of all, identify and determine the type of soil in the lay of their allotted area/plot.  

Some soils are rich in many of the essential foods required by plants, others abound in certain elements but are deficient in others.  

It is prudent for farmers to assess the pH value of their soils to ensure that they have the most favourable chemical environment suitable for the plants they are, or intend to grow.  

The pH scale of the soil is an expression of the chemical measure of hydrogen-ion concentration.  

Simply put, the pH is the indication of the alkalinity and acidity – or sweetness or sourness, of the soil.  

As a general observation, most plants prefer soil of an alkaline nature.

All soils in Zimbabwe will benefit from the addition of humus and organic matter.

Humus – is nature’s own God-given fertiliser.  

By definition, humus comprises a dark brown or black colloidal mass of partially decomposed organic matter in the soil.  Agronomists and agro-practitioners are aware of how humus is an important ingredient for soil conditioning.  

It improves the fertility and water retention capacity of the soil.

Stony soils can be moderated and reconditioned by removing larger stones. 

However, experienced farmers will know to leave smaller stones that are an essential part of fertile soil; adding to its porosity and improve moisture retention

Restricted knowledge on the use of fertilisers and soil types, often hinders maximum beneficiation of the land.  

The three basic requirements of the soils that both manure and fertilisers can supply are nitrogen, phosphates and potash that induce healthy growth and increases resistance to disease in plants while also inducing drought and cold tolerance and thus improve the quality of the crops.

Phosphate gives a good start to crops; assisting in strong root and shoot formation and encourages early maturing.  

Nitrogen on the other hand, promotes growth and increases the final yield of crops.  

A well-balanced compound fertiliser is recommended to suite farmers’ soil needs

In common with farmers, plot holders and horticultural gardeners is the development of soil conservation.  

The first and most obvious way for farmers to maintain soil is to maintain and conserve what they already have.

Farmers must never allow their soil to be washed away – it takes too long to replace.  

Therefore, soil conservation and preservation of other natural resources should be high on the agenda of indigenous and new commercial farmers in Zimbabwe. 

Dr Tony Monda is Zimbabwean socio-economic agronomist analyst and scholar.  He is currently conducting veterinary epidemiology, agronomy and food security and agro-economic research in Zimbabwe and southern Africa.  

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