Agri Kultuur December / Desember 2018 - Page 15

Table 1: Available organic and inorganic nutrients (kg/ha) and value (R/ha) in a soil under warm season cover crops Cost R / Kg Nutrient Nutrient value (kg/ha) Total Organic Inorganic 17 Nitrogen 23.3 R 396 R 133 R 263 40 Phosphorous 42.5 R 1 700 R 72 R 1 628 15 Potassium 209.7 R 3 146 R 0 R 3 146 R 5 242 R 205 R 5 037   Saving Table 2: Available organic and inorganic nutrients (kg/ha) and value (R/ha) in soils under cool season crops Price R / Kg Nutrient Nutrient value (kg/ha) Total Organic Inorganic 17 Nitrogen 19.9 R 339 R 156 R 183 40 Phospho- rous 54.6 R 2 185 R 84 R 2 101 15 Potassium 285.6 R 4 284 R 0 R 4 284 R 6 808 R 240 R 6 568   Saving Table 3: Salient analytical data for the degraded soil taken during the growing season of a summer cover crop mix Soil pH (H2O)   7,3 Soluble Salts mmho / cm 0,3 Excess lime rating   1 Soil Organic Matter (SOM), LOI %    0,8 Calcium ppm 187 Aluminium extractable ppm 651,6 Phosphorous Saturation % 4,6 Iron extractable  ppm 378 Table 3 shows that phosphorous saturation is below 5% which indicate that additional inorganic phosphorous fertiliser is needed. With less than 1% SOM the soil can be seen as highly degraded due to a long period of continuous tillage practices. The establishment of a multi-specie CC system are seen and applied as the start of a process to build-up the degraded soil, which could take up to 7 years or more, depending on the situation and the quality of CA application, the soil type and the climate. However, it is anticipated that this type of CC system, rotated every second year by a cash crop producing high amounts of residues (such as maize), could quickly restore soil ecosystem functions and decrease the rehabilitation or transformation period to 3 or 4 years. AgriKultuur |AgriCulture In a high temperature, low rainfall environment such as Ottosdal, the high amounts of CC residue would almost immediately have had a positive effect on the soil water content with much higher infiltration rates and much less water loss through evaporation. During the following few years, the presence of a diversity of plant roots in the soil will most probably have a positive impact on soil microbial diversity and activity, including mycorrhizas, which are highly dependent on a host and living roots. These effects are currently being measured 15