Agri Kultuur December / Desember 2018 - Page 16

Photo 1: Soil with surface crusts and signs of severe erosion At the stage when the cover crop was fully developed, photo 2 was taken on the 14 April 2016; the crop yielded an average biomass production of 12t DM/ha. Photo 2: Fully developed mixed summer cover crop system in on-going research in Grain SA’s on-farm CA trials across the country. The establishment of perennial pastures is another possible solution, as part of the crop diversity within integrated crop-livestock systems, to facilitate the restoration process. From a degraded soil to commercial maize production colonization of mycorrhizal fungi. It has been shown in the past that only 20% P fertiliser is taken up during the first year after application, while soil microbes provide plants with the amounts of nutrients required. 12 kg of K/ha - since there is sufficient amounts of K in the soil, this application was just to establish strong vigorous seedlings; additional Sulphur and Zinc were also applied. No further inputs as far as soil fertility management were deemed necessary. This was due to a great supply of nutrients in the cover crop residues that will be made available as the CC biomass decomposes through microbial activity. In order to put this field back into maize production (as was aimed for), the following fertilizer application rates (side dress) was used to establish the maize crop aiming for a 5 t/ha yield in the 2016/2017 season: 33 kg of N/ha – this amount of N will cover a yield target of only 2 ton/ha; the remaining N required will be provided through nutrient cycling and C decomposition of the CC mix’s DM and roots. Depending on the production of the CC, a saving of 70-80 kg/ha of N can quite easily be attained during the first year (see Table 1, Part 1). 18 kg of P/ha – this amount of P will cover a yield target of 5 ton/ha; from the Haney soil analysis it is clear that C content and microbial biomass activity is not yet sufficiently restored to recycle and/or release sufficient soil P to support plant P requirements for a yield target of 5 ton/ha. It is expected that more P will be released from the soil in the next couple of years through biological processes and AgriKultuur |AgriCulture Photo 1 shows the soil surface before cover crops was planted. Low levels of cover with a soil surface crust and erosion can be seen. The photo was taken on 27 January 2016, just before the cover crops were planted. Photo 3 shows the CC residues (left standing) killed by the winter frost, taken on 2 September 2016. A decision was made not to flatten it because of the positive effect the standing residues would have had on wind and water erosion. The cooler soil under the residue cover will also benefit the water cycle due to the lower evaporation from the soil surface. 16