Short-term effects of tillage and manure on some soil physical properties and maize root growth in a sandy loam soil in western Iran

Abstract

Careful soil management is the key to sustainable agricultural production. Tillage practices are critical components of soil management systems which significantly affect soil characteristics and plant development. There is little information concerning the combined impacts of tillage systems and manure application on soils and root development in the western part of Iran. A study was conducted to investigate short-term changes of soil bulk density (BD), soil cone index (CI) and maize ( Zea mays L.) root length density (RLD) under different management regimes. The study was carried out on a sandy loam soil (fine loamy, mixed, mesic Calcixerollic Xerochrepts, USDA). The effects of three tillage systems (no-till, NT; chisel plow, CP; and moldboard plow, MP) at three composted cattle manure rates: 0 (M0), 30 (M30), and 60 Mg (dry weight) ha −1 (M60), were studied on BD, CI and RLD. The experiment was carried out in a split-plot design with tillage as the main plot and manure application as the sub-plot. Three replicates of the treatments were applied in a randomized block design. The soil and root samplings were done when 100% of the tassels appeared. Tillage methods and manure applications had significant effects on RLD in the upper soil layers. Tillage affected RLD in the order of MP > CP > NP and manure effects on RLD were in the order of M60 > M30 > M0. The effects were not significant for the lower soil layers. The MP system had higher values of RLD with lower values of both CI and BD. The NT system resulted in lower RLD and higher CI and BD values. The increased BD and CI of the topsoil in the NT treatment restricted root growth. The mean BD values (average of all soil layers and manure treatments) were 1.43, 1.37 and 1.26 Mg m −3 for NT, CP and MP, respectively. Adding manure to the soil significantly increased RLD in the order: M60 > M30 > M0. There were also significant differences in CI and BD among manure treatments. The mean CI values (average of all soil layers and tillage systems) were 1.43, 1.22 and 1.06 MPa for M0, M30 and M60, respectively. The positive diminishing effects on CI and BD of manure applications may be attributable to manure incorporation and improvement of the physical quality of the soil with low organic carbon content. The significant overall relation between RLD and CI demonstrated the dominant effect of soil mechanical impedance on root growth. The manure application seems to be able to compensate to a significant degree for the increased mechanical impedance with no-till. The results indicate short-term beneficial effects of manure application on maize root length density as well as on soil physical properties when combined with the tillage systems.