Variation in soil strength and rooting characteristics of wheat in relation to soil management

Studies on soil strength and rooting characteristics of crops are important for water and nutrient budgeting and also for deciding the adoption of suitable soil management practice for sustainable crop production. In the present field trial, the variation of soil penetration resistance (PR) with soil water content (SWC (w/w)) and bulk density (BD) changes under bed and conventionally planted wheat was studied on a sandy loam soil of research farm of Indian Agricultural Research Institute, New Delhi. The differences in root characteristics of both systems were also compared. The results showed that, in general for all SWC, with increase in BD from 1.2 to 1.6 Mg m− 3, PR increased but the increase was more sharp in conventional than in bed planting system. It was further seen that, at all BDs, the critical soil strength of 2 MPa arrived at higher SWC in conventional as compared to bed planting. It thus indicated that root growth continued normally at relative lower SWC in bed planting as compared to conventional planting. Multiple regression analysis of soil penetration resistance as a function of BD, SWC and soil depth showed that SWC alone accounted for 59% variation and along with BD accounted for 93–96% variation in PR. Addition of depth did not improve the correlation. Sensitivity analysis of multiple regression equation predicting penetration as a function of SWC and BD indicated that PR was more sensitive to SWC changes than BD changes. Lower sensitivity indices for both SWC and BD in bed planting than in conventional planting indicated relatively lesser change in PR per unit change in SWC or BD in bed system. Computer aided root length scanning system ‘RHIZO’ was used to study rooting characteristics. Analysis showed that root characteristics including root length density, average root diameter, surface area density and volume density of roots of wheat up to 30 cm were significantly higher in bed over conventional system. In both systems, nearly 70% of root length density and 76–82% of root surface area was confined in upper 30 cm. It was further seen that more than 70% of total root length was in root diameter range below 0.3 mm. Hence, it was concluded that sowing of wheat on beds reduced mechanical impedance and increased root growth in upper 30 cm of soil, which ultimately resulted in higher crop yield.