Influence of Tillage Method and Residue Management on Yield and some Agronomic Characteristics of Wheat in Water Stress Conditions

Influence of Tillage Method and Residue Management on Yield and some Agronomic Characteristics of Wheat in Water Stress Conditions
Abstract
Conservation agriculture is based on three principles of minimum soil movement, preservation of part of crop residue and crop rotation for sustainable profit. In order to study effects of tillage method, residue retention and water stress on grain yield, yield components and water use efficiency of wheat, an experiment was conducted in Jolg-e-Rokh research station (Torbat-e-Heydarye, Razavi Khorasan Province) in 2015-16. The farm has been managed under the conservation agriculture system from 2012 (with similar treatments of this experiment and fixed plots in wheat-clover-Sugar beet-barley-forage maize crop rotation). The experiment was conducted using split split plots based on randomized complete block design with three replications. Treatments included different tillage methods (no tillage, minimum tillage and conventional tillage), residue retention rate (0, 30 and 60 percent) and water stress (irrigation with 50, 75 and 100% water requirement). The studied characteristics included grain yield and yield components, harvest index, water use efficiency, and normalized difference vegetation index. The results showed that various tillage methods were significantly effective on number of seeds per spike, grain yield and water use efficiency, while residue treatment had no significant effect on yield and its components. Water stress treatment had a significant effect on 1000 seeds weight, grain yield and water use efficiency. The yield in minimum tillage method (6551 kg ha-1) was superior to no tillage method (4626 kg ha-1) and conventional method (4857 kg ha-1), 41% and 35% respectively. The minimum tillage method had the highest rate of WUE (1.71 kg / m3), and in comparison with no tillage method (1.20 kg / m3) and conventional method (1.26 kg / m3), superiority 42 and 36 percent respectively. Grain yield under water stress of 50 and 25% of water requirement, was 4633 and 5506 kg/ha and showed a decrease of 21% and 7%, respectively, however, the levels of water stress of 25% and control treatment were similar statistically. According to the results, it seems that the minimum tillage method and maintaining 30 percent of the crop residues can be recommended to farmers.
Keywords: Conservation agriculture, Crop rotation, Reduce tillage, Water use efficiency

Introduction
The conventional agricultural system, which is a type of intensive farming, has reduced soil fertility and endangered sustainable production in agricultural systems and the environment, for this reason, it is inevitable to change the conventional methods of agricultural production in order to achieve sustainable production and food security. Since the 1980s, a new agricultural system called Conservation Agriculture has been proposed as a human policy to confront the challenges of production. According to the Food and Agriculture Organization, conservation agriculture is a way to preserve crop production resources that seeks to achieve the benefits of sustainable acceptance along with high production (FAO, 2007). Conservation agriculture system is based on three principles of minimum soil movement, retention of rational amounts of crop residue and crop rotation, for sustainable profitability (Hobbs et al.,2008). The analysis of a 14-year long period, which was conducted by Fileccia on wheat yield after a system change from conventional tillage to no tillage, showed a 28 percent improvement in this system (Fileccia, 2009).
Materials and Methods
In order to studying effects of tillage method and residue retention on yield, yield components and water use efficiency of wheat in water stress conditions, this experiment conducted in Jolg-e-Rokh research station (Torbat-e-Heydarye, Razavi Khorasan Province) in 2015-16. Used farm, has been managed under the conservation agriculture system from 2012 (with similar treatments of this experiment and fixed plots in wheat-clover-beet-barley-forage maize crop rotation). The experiment was conducted as split split plot in randomized complete block design with three replications. Treatments were Tillage method (no tillage, minimum tillage and conventional tillage), residue retention rate (0, 30 and 60 percent) and water stress (50, 75 and 100 percent of irrigation water). Use the pishgam cultivar at a rate of 250 kg/ha and a specially designed planter (made by GASPARDO Corporation) for planting without tillage was used. Each experimental plot was 40 meters long and had 24 rows with lines spaced about 20 cm. The irrigation system was T-tape.