Physical effects of direct drilling equipment on undisturbed soils

摘要

Abstract A method of measuring soil relative humidity at the seed-soil zone in direct drilled grooves is described. Grooves were formed by several combinations of three selected coulter types and seed covering methods. In-groove soil relative humidity was measured at the same time when seeds were growing under controlled constant climatic conditions in a soil initially under severe moisture stress. A negative correlation coefficient of r = 0.75 was found between the in-groove relative humidity and combined counts of seedling emergence and sub-surface unemerged seedling survival. The ability of seed grooves to retain moisture vapour was described in terms of'moisture vapour potential captivity' (MVPC). A minimum value of MVPC = 0.4 was suggested for the dry soil of this experiment. A mathematical model relating in-groove relative humidity and seedling emergence plus sub-surface seedling survival was developed. Specifications of coulter design and seed covering methods were suggested which might create bett...