Nutrient uptake by crops might be limited when nutrients are stratified, especially in semi-arid or Mediterranean regions. To reduce stratification, infrequent tillage could be considered. However, there is a paucity of information on the effects of long-term infrequent tillage on the stratification of soil chemical parameters.
This study aimed to assess the effects of long-term infrequent tillage on the stratification of selected soil chemical parameters to a depth of 300 mm. The research was conducted on a long-term (42 years) research site at Langgewens Research Farm in South Africa.
Seven tillage treatments were investigated: continuous mouldboard ploughing to a depth of 200 mm, tine-tillage to 150 mm, shallow tine-tillage to 75 mm, no-tillage, shallow tine-tillage every second year in rotation with no-tillage, shallow tine-tillage every third year in rotation with no-tillage and shallow tine-tillage every fourth year in rotation with no-tillage.
Tillage treatments had differential effects on the distribution of soil chemical parameters. The mouldboard plough prevented stratification of most soil chemical parameters, such as soil acidity, soil organic carbon (SOC), extractable P, exchangeable Ca and Mg and cation exchange capacity (CEC). However, mouldboard ploughing also led to significantly lower SOC stocks and extractable P stocks.
The SOC stocks and extractable P stocks of the no-tillage treatment were not significantly different from those of the infrequent tillage treatments. Overall, the infrequent tillage treatments were no better (P > 0.05) than the no-tillage treatment as infrequent tillage could not effectively ameliorate the stratification of most soil chemical parameters and did not increase the stocks and stratification ratios of SOC and extractable P.
3 farmers share why they switched tillage practices
Pressures from population growth, changing diets and climate change are driving transformation of our global food production to ensure more efficient, reliable and sustainable production. In South Africa, arable land for crop production and permanent pastures accounts for 10–12% of the total land surface. South Africa is classified as semi-arid, with the average rainfall below the global average. Accordingly, dryland agriculture must identify and promote management systems with high water-use efficiency; this is crucial in a country with a debilitating water deficit. Climate change is expected to exacerbate climate variability in South Africa, and thus exert even more pressure on rainfed dryland production.
Conservation Agriculture (CA) is a holistic set of principles aimed as a guide to sustainable, reliable and climate-smart farming practices. Although initially established as a guide for grain farmers, its principles are also applicable to other agricultural commodities. The three principles of CA have been extensively promoted, with successful adoption and adaptation in many countries. This review highlights the results of research to date and the challenges for practising rainfed conservation agriculture in South Africa.
Nutrient uptake by roots accounts for nearly all nutrient uptake under natural and cultivated conditions, but foliar uptake is important under some circumstances, e.g., in densely populated areas where NH3 gas and other nutrients in dust are significant, in nurseries where nutrients are applied as foliar sprays, and in forest plantations where foliar sprays are used to correct some micronutrient deficiencies.
Nutrients are taken up by roots mainly as inorganic ions from soil solution. The rate of uptake depends primarily on the concentration in the soil solution immediately adjacent to the root. The rate of nutrient uptake is independent of the rate of water uptake, but the concentrations of nutrients at root surfaces depend strongly on soil water content. Soil water content is important because it affects root growth and nutrient transport to the root surface in both the water flux created by transpiration (called mass flow), and the diffusive flux towards or away from the root. The forms of ions taken up by roots differ somewhat with plant species and growing conditions, and they are regulated by a combination of soil processes, the importance of which depends on the nutrient in question. These processes include organic matter mineralization/immobilization, mineral dissolution/precipitation, solid/liquid equilibria, oxidation/reduction reactions, and solid, liquid, and gaseous inputs and outputs.
