Tillage and fertilizer effects on root growth of wheat and cotton on a sandy clay loam in Pakistan

Tillage methods and fertilizer application affect root development, and the yield and quality of crops. Effects of tillage and fertilizer rates on root length density (RLD) of wheat (Triticum aestivilln L.) and cotton (Gossypium hirsutum L.) and macronutrient content of wheat grain grown on a sandy clay loam (fine-loamy, mixed, hyperthermic Typic Haplargids, USDA; Luvic Yermosol, FAO) were evaluated in the semi-arid region of Pakistan. Effects of three tillage methods as main plots and three fertilizer rates as sub-plots were studied in a split plot configuration from 1996 to 1999. Tillage treatments were (1) minimum till (MT), (2) conventional till (CT) and (3) deep till (DT). Three rates of NPK fertilizer (kg ha(-1)) were 60-20-25 (low), 120-40-50 (medium) and 180-60-75 (high) for wheat; and 85-19-25 (low), 170-38-50 (medium) and 255-57-75 (high) for cotton. Tillage method had no significant effect on the RLD of either wheat or cotton at 0-0.15 m depth. However, greater RLD was obtained for DT in cotton and for NIT in wheat in the subsoil. The RLD of cotton was less for high than medium and low rates of fertilizer at 0-0.15 m depth, and the reverse was true for 0.15-0.3 m depth. A similar trend was observed for wheat. Generally, almost 50% more RLD was measured in 0 to 0.15 m than 0.15 to 0.30 depths for both crops. During 1999, the grain N concentration was higher in DT than MT and CT; the latter two were statistically similar. Grain N content increased with increasing fertilizer rates. During 1995, the grain P concentration was more in MT and CT than DT treatments; however, fertilizer rates did not affect grain P and K concentrations. The RLD of wheat was positively correlated with grain and straw yields, and uptakes of N, P and K. In contrast, the RLD was negatively correlated with K concentration of wheat grain and that of soil penetration resistance. (C) 2003 by The Haworth Press, Inc. All rights reserved.