Relationship between soil structure, soil cultivation, nitrogen uptake and crop growth. III.—Effects of cultivation on the porosity of soil and its compactness and on crop development and yields

Abstract

AbstractCultivation treatments examined consisted of deep ploughing (8 in.), shallow ploughing (4 in.) and surface treatment (2 in.) with a tine cultivator.The non‐capillary porosity of the soil was affected more than the capillary porosity by cultivation. Deep‐ploughed plots showed higher percentages of total and non‐capillary pore space than did shallow‐ploughed or tine‐cultivated plots at depths of 0–2, 2–4 and 4–8 in. At the 8–12‐in. depth no significant differences in porosity due to the different treatments were apparent.Effects of depth of cultivation on non‐capillary porosity persisted throughout the growing season, remaining longer in a dry than in a wet season.Variation in the compactness of soil with time was unaffected by the type of cultivation.As compared with tine cultivation, deep ploughing increased the numbers of branch roots in wheat, but no significant differences in this respect between deep and shallow ploughing existed.There were no apparent differences between the types of cultivation in respect of numbers or lengths of main roots or dry weights of roots and shoots in wheat, or of ‘stand’, dry weight or final yield in wheat and swedes, except that in the earlier stages of growth of swedes on unmanured plots, deep ploughing produced greater weights of crop than did either shallow ploughing or tine cultivation. The top/root ratios in wheat were higher after ploughing (deep or shallow) than after tine cultivation.Neither aggregation (based on crumbs >0.5 and 0.5–0.05 mm.) nor pore space (total, capillary or non‐capillary) was associated with numbers of roots in wheat or with any other plant characteristics examined in wheat or swedes, in the two soils used.