Independent Soil & Crop Consultant, Thomas Strydom, answers a few questions about the current state of the soil in various regions of South Africa.
Droughts can have certain positive as well as negative impacts, as they affect the soil’s chemical, physical and biological environment in various ways. A positive may be that it is one of nature’s ways of replenishing the soil, because of less chemical degradation of nutrients due to smaller crop yields and less nutrient extraction, as well as physical protection of soil with less natural water compaction in sandy soils and lower compaction by tractors and implements, in effect, putting the soil in “a resting period”. During these periods there is also less leaching of important elements such as nitrogen, potassium and sulphur. It is almost impossible for a farmer to see or experience any drought as a positive; unfortunately, they remain part of nature’s cycle. With excessive heat, organic materials on top of the soil can burn to “ash” rather than create humus in the top 200mm. In such cases, nitrogen in the soil will also be used by organisms at the expense of plants. Damage after hard rain, which occurs sporadically, followed by strong winds, is another major problem. Wind erosion is common in times of drought. Certain types of sandy soils in the Western parts also tend to harden in drier years, when fine sand particles become firmly pressed into each other. Natural soil compaction occurs that has a negative impact on root development and distribution of roots through the soil profile. It is also essential to look at the chemical composition of the soil through lab analysis and make the necessary corrections. Soils do not always have effective depth for root development and for this reason, chemical balances must be optimal to ensure better plant growth. By utilising grid sampling, chemical variations can be corrected and eventually eliminated.
Due to various problematic cultivation practices there are unfortunately big areas that show compacted layers at depths from 250 to 400mm. This has a huge impact on root development and also the ability of the soil to utilise the nutritional elements that are available. Farmers should focus on detailed grid soil analysis to ensure that the soils are managed efficiently as they can become very difficult to fix. Soils only have the capacity to handle a certain amount of lime and if the need is higher, due to acidity, pH and calcium/magnesium levels, it can be very difficult to overcome the problems in a short period of time. Inclusion of other elements can also be adversely affected, as the ability of plants to capture nutrients decreases drastically at lower pH levels. Adequate calcium levels and more alkaline soil gives plants the ability to handle stress and dry periods better, and up to 2 weeks longer.
There are many variations and problems with regard to soil; producers do not always know and understand the variations and characteristics, and generally deal with them in the same way as their neighbours or predecessors. In many cases, they fail to make sure what is best for their specific farming and environmental conditions. By gathering good information and judiciously respecting nature, the correct steps can be taken, with less mistakes and not so many school fees to be paid.
Read another blog from Arthur: Developing a precision farming system in South Africa
It is important that a holistic approach be followed when it comes to field management.
If possible, producers should collect good information and then decide what corrective action is needed and what should be planted. Information such as soil analysis, profile soil inspections, moisture availability in the soil, crop rotation planning as well as input product prices, should be taken into account before deciding the way forward. Only once all the information has been obtained is it possible to decide which way to go. It is essential to determine what the most important factors are and where the greatest risks lie and save where you can without directly harming profits. Plants growing on a healthy fertile medium can handle stress conditions better and present the opportunity to realise above normal returns in good circumstances.