Tillage effects on corn in sandy soils in relation to water retentivity, nutrient and water management, and seasonal evaporativity

Abstract

Low water retention, excessive permeability, high mechanical resistance to growing roots and low fertility of sandy soils causes water and nutrient stresses in crops. These can be alleviated by enhancing root development in the soil profile and/or regulating water and nutrient supplies. This study reports the results of a series of experiments on deep tillage influences on corn in relation to water retentivity of soils, nutrient and water management, and evaporativity (E 0). Tillage effects on winter (low E 0) corn were assessed in four soils differing in available water capacity (AWC), viz. 8 cm (Soil 1), 10 cm (Soil 2), 13 cm (Soil 3), and 15 cm (Soil 4) m −1 soil depth. In a given soil, yields were associated with the size of the root system (root length index (RLI)); while across soils they were also influenced by AWC. In Soil 1, 30 cm deep chiselling increased yield from 0.6 t ha −1 with no-till to 2.1 t ha −1. Deep tillage benefits were less than 20% in Soil 2 and almost absent in Soils 3 and 4. Water accessibility index (the product of RLI and AWC) accounted for large variations in yield due to soil water retentivity and tillage effects. With frequent and small irrifations and at 160 kg N ha −1, increasing the depth of tillage from 10 to 30 cm in Soil 1 increased the yield from 2.8 to 4.7 t ha −1 in the unmanured plots and from 3.8 to 5.4 t ha −1 in the manured plots. Comparable yields with 80 kg N ha −1 and 30 cm deep chiselling and with 240 kg N ha −1 and 10 cm deep tillage indicate that tillage increased the utilization of applied N. Additional benefits of the combination of deep tillage with frequent and small irrigations in Soil 1 suggest that to avoid intermittent water stress even in the winter season, tillage should be accompanied by proper irrigation management. Interestingly, tillage showed substantial benefits to simmer corn in Soil 2, in which tillage effects on winter corn were either very low or absent. In Soil 4, the benefits from deep tillage were much less, even in the intense summer. These results suggest that corn responses to deep tillage are influenced by the interplay of soil water retentivity and seasonal E 0 which together determine the frequency and extent of water stress.