Effects of Tillage Systems and Growth Cycle of Wheat Cultivars on Soil Water Conservation and Crop Yield.

A study was started to investigate the interactions of tillage systems and growth cycle of wheat cultivars (long (LC), intermediate (IC) and short (SC)) on water consumption, water use efficiency, grain yield, yield components, and harvest index. Two tillage systems were used: no-till (NT) and conventional tillage (CT). The latter consisted of disk plough used in early fall prior to seeding.  The experiment was carried out in the semiarid temperate region of Argentina (36°46' S, 64°17' W). The soil was an Entic Haplustoll, with a sandy loam texture. At sowing, 50 kg ha^-1 of diammonium phosphate (DAP) was applied. Volumetric soil water content was measured at 20-cm-depth intervals to the depth of the petrocalcic layer.
The amount of water conserved during the fallow period was highest under NT system.  Water consumption was lowest under CT and SC cultivars and highest under NT and LC cultivars. Water use efficiency varied between 6.6 (NT-SC) and 4.0 (CT-LC) kg ha^-1mm^-1. Highest grain yield were obtained with NT and within each tillage system with SC cultivars. Yield increase was mainly due to an increase in the number of kernels per spike. Harvest index was highest in NT-SC (0.24) and lowest in CT-LC (0.14).