Grain Guide 2018

Conservation Agriculture and soil fertility management One of the good agricultural practices (GAPs) associated with CA is integrated soil fertility management (ISFM) , which essentially depends on locally adapted CA principles and practices to build-up soil health, allowing producers to reduce the use of fertilisers, while sustaining good and stable yields and increasing profitability. This concept of ISFM emphasises the following:  Maximisation of nutrient use efficiency.  The enhanced access of soil nutrients to plant roots.  The response of soil as a living ecosystem.  The role of sound locally adapted soil management practices enhancing ecosystem functions and services leading to improved soil fertility.  Well-adapted, disease- and pest-resistant germplasm.  Other good agricultural practices. The critical soil ecosystem processes involved are transformation of carbon (mineralisation), cycling of nutrients, maintenance of the structure and fabric of the soil, and biological regulation of soil populations. Ways to increase nutrient use efficiency (NUE) Nutrient use efficiency, which may be defined as the yield obtained per unit of available nutri­ ents in the soil (supplied by the soil + fertilisers), could be improved as follows:  Adjustment of fertiliser application rates based on (natural) soil fertility levels taking account of SOC level, organically bonded nutrients, nutrient cycling and/or previous cropping practices, especially legumes, and their residue biomass.  Apply fertiliser at the right time and place and using the right source.  Plant crops at the right planting density having enough plants to ensure optimal and efficient nutrient access and yield. In CA higher plant­ ing densities (around 30% higher than the norm) or at least above 22 000 p/ha ensures effective use of soil nutrients and water in the whole soil profile and surface area, while reducing temperature at soil surface level. CA Principles and practices enhancing Integrated Soil Fertility Management Many producers world-wide have achieved large improvements in soil health and -fertility in a relatively short time. What are these farmers doing differently? Minimum soil disturbance  Physical soil disturbance, such as tillage, isdestructive and disruptive to soil micro­ bes and creates a hostile, instead of hospitable, place for them to live and work (See Photo 1 on page 75).  The soil may also be disturbed chemically or biologically through the misuse of inputs, such as fertilisers and pesticides. This disrupts the symbiotic relationship between micro-organisms and crop roots. By strategically reducing chemical inputs, we can take advantage of these soil ecosystem services to allow plants to freely access essential nutrients. Diversify with crops and animals  Sugars made by plants, through the miracle of photosynthesis, are released from their roots into the soil as liquid carbon and traded to soil microbes for nutrients to support plant growth. 75 72 GRAIN GUIDE 2018 Fertiliser