Agri Kultuur August / Agustus 2016 | Page 10

Dr Marcellous le Roux Department of Agronomy (Faculty of AgriSciences) I t is often reflected that the only constant in life is change. Change implies that things are dynamic and therefore always in a state of transition. It would appear that agriculture, globally, also finds itself in some state of fluidity, with a radical shift urged by the demands of the day and an eye on future generations. With these dynamics at play, agricultural systems are under pressure to sustain productivity within narrow environmental confines. ‘Soil health’ has been compromised through inappropriate farming practices, including continuous mono cropping, which have led to declines in soil fertility, accelerated soil erosion, and degradation of arable lands. It is evident that soil management influences soil microorganisms and soil microbial processes through changes in the quantity and quality of plant residues enter- ing the soil, their seasonal and spatial distribution, the ratio between above- and belowground inputs, and changes in nutrient inputs. Despite this, soil ‘quality’ as it pertains to biological fertility has been neglected. There is a resurgence of interest in environmentally prudent, sustainable agricultural practices. Inherent in the concept of best management practices (BMP) is the ideal to improve resource use efficiency, to mitigate environmental impact and/ or increase farm profitability. In light of the aforementioned argument, such an approach inevitably needs to be intricately linked to the activity of soil biota, especially microbial communities that are largely responsible for the nutrient decomposition processes and the subsequent nutrient cycling that ensue. Conservation agriculture (CA) has emerged as a potential means to improve soil organic matter (SOM) and is widely endorsed to pave the way for systems change in many agrarian societies, to whom agriculture is the bloodline of their livelihoods. CA prioritises protection of soils from degradation processes and is underpinned by three major principles – (reduced) tillage, crop rotation, and residue management to advance agricultural intensification on a sustainable trajectory. Minimum soil disturbance and maintaining permanent soil cover are two of the foremost approaches that can mitigate the effects of soil degradation (see Figure 1). It does this through moderating soil surface conditions, which could translate into crop yield improvements and increase net farm benefits due to reduced production costs. In addition, permanent soil cover moderates soil temperature variations,