Some Residual Soil Effects of the Three Years’ Grazing Trial

Both return of excrement and application of nitro-chalk in grazing trial increased the soil organic carbon significantly. Available soil phosphate was increased by superphosphate applied to ley and by the return of dung and urine, fertilizer phosphate being better in effect than the return of excrement. Return of excrement and potash applied to the ley increased the available soil potassium. Its exhaustion was prominent at the highest level of ley nitrogen and it was more severe with higher level of phosphate applied together to ley. However, when excrement was combined with higher levels of nitrogen and phosphate the available potassium was adequate. Potato yield increased due to the return of excrement and residual potassium where no fertilizer was applied. The residual N₁ and N₂ levels gave lower yields than N₀. There were no marked variations from the original treatments on potato yield where 9 cwt per acre of complete (12-12-18) fertilizer was used. Ley phosphate gave somewhat lower yield. Where no fertilizer was applied at planting of potato, a response to ley phosphate was found in the yield of wheat (grain and straw) and response to ley potassium was noticed on both sections for wheat. Response to return of excrement was similar to ley potassium.