Agri Kultuur December / Desember 2018 - Page 17

Photo 3: A 100% cover by the mixed summer cover crop residues Photo 4: Field with summer cover crop residues just before planting the maize crop Photo 4 was taken just before the maize was planted on 12 December 2016; note that the easy decomposable leaves containing the most nutrients were already decomposed by the microorganism. Only the woody plant material containing the less digestible tannins and lignin fragments in the residues were left. It is in decay or decomposition that this organic matter becomes useful as it becomes the fuel for ‘bacterial fires’ in the soil, which operates as a factory producing plant nutrients. Photo 5 shows the maize crop at tasselling and silking stage with no signs of any nutrient deficiencies. The lower older leaves remain green. By April 2017 the predicted maize yield on this field was 7.5 ton/ha, indicating by all standards to a successful regeneration (restoration) of a degraded soil into full maize production using the principles of CA and ISFM. A good tool to monitor soil fertility or the uptake of plant nutrients is leave analysis (at this growth stage); plant nutrient levels should match the values shown in Table 4. Table 4: Critical plant nutrient levels in maize leaves Critical plant nutrients levels in leaf opposite and below the ear at tasselling % of DM Ppm of DM N P K Mg Ca S Zn Fe Mn B 2.9 0.25 1.9 0.15 0.4 0.15 15 25 15 10 Source: Hoeft & Peck, 1991 Conclusion This case study has demonstrated that CA facilitates the successful application of ISFM, the recovery of critical soil ecosystem functions and the restoration of degraded soils. This process requires from producers a quality implementation and adaptation of AgriKultuur |AgriCulture CA practices such as crop diversity and more specifically, multi-specie cover crop systems. It also requires an understanding of soil health and a long-term vision on soil restoration or regeneration, especially under dry and sandy soil conditions. 17