Effect of Tillage Systems and Residue Management on Soil Water Conservation, Yield and Yield Components of Wheat

Soil is one of the most important components of production, food security, self-sufficiency and national economy. Soil of semi-arid regions, which most of Iran's agricultural lands are located in these areas, are poor in terms of organic matter. The soil tillage operations are carried out by means of moldboard plow and removal of plant residue in most of the agricultural systems. This operation, called conventional tillage, requires not only high energy but also damages to soil physical properties and erosion in the long-term. Conventional tillage does not provide good environmental conditions to maintain moisture in the soil due to the impossibility of managing plant residue in the soil surface. In addition this tillage increases the evaporation and losses of soil water content and reduces the soil organic carbon as a result conventional tillage reduces the physical, chemical and biological characteristics of the soil. The objective of this study was investigation of effect of conventional and reduced tillage systems and management of tomato residue on soil water content, yield and yield components of wheat.

The experiment was conducted as split plot based on randomized complete block design with three replications at the Agricultural Research Station, Ferdowsi University of Mashhad, during growth season 2017-18. Tillage system (in two levels i.e. conventional and minimum tillage) and tomato residue retention (0, 30 and 60%) were in main plots and sub plots, respectively. The sowing date was 11th November in 2017.Sampling was done at harvest time and included plant height, spike number.m-2, spike length, grain number per spike, 1000 grain weight, grain yield, biological yield and harvest index. During the growing season, soil water content in 0-20 and 20-40 cm depth was measured by the soil moisture meter (PMS-714 model) two days after irrigation. Data were analyzed with R software; obtained averages compared with Duncan’s multiple range test at the 5% probability level.

The results showed that the effect of tillage system was significant on soil water content in 0-20 cm depth two days after forth irrigation, soil water content in 20-40 cm two days after fifth, sixth and seventh irrigation, spike number.m-2, grain number per spike, grain and biological yield. Maximum of this traits were obtained in reduced tillage due to increased soil nutrition, improved physical condition of the soil and soil water status. However, the effect of management of tomato residue on any of the studied traits was not significant. This could be due to reducing microbial activity, in complete decomposition of plant residues and reducing available nitrogen.
The interaction effect between tillage system and tomato residue was significant on soil water content in 0-20 and 20-40 cm depth two days after forth and third irrigation, respectively, grain number per spike, 1000 grain weight and grain yield. Reduced tillage and 60% of tomato residue showed that maximum of soil water content and 1000 grain weight (38.4 g).Maximum of grain number per spike (61.9) and grain yield (7120. 7 kg.ha-1) were obtained in treatment of reduced tillage and 30% of tomato residue.
Conclusions  
The results of this study indicate that in order to achieve maximum grain yield and less damage to the physical and chemical properties of soil, the implementation of reduced tillage and maintenance of 30% of tomato residue is recommended in the studied area. In general, due to climate change and water resource constraints in the country, conservation tillage and residue management practices are a good way to maintain resources and sustainability.