اثر عمق کاشت و مالچ بر ظرفیت نگهداری رطوبت خاک درمراحل مختلف رشد نخود تحت شرایط دیم

Introduction
In dry areas, water is the limiting factor in improving agricultural production. Saving the annual precipitation in the soil is very effective in dryland farming. The amount of rainfall that infiltrates the soil depends on the amount of soil permeability and runoff. The surface remains will be able to better permeable prevent runoff and raindrops and reduce erosion. In addition, evaporation can be reduced about 40 to 70 percent and this water is available for plants. Moreover, mulch keeps sufficient moisture to increase the microbial activity, rise mobility and better food for plant growth. Therefore, various tools and techniques should be used in rain-fed conditions to reduce risk of water losing and create sustainable performance. In this work, some types of mulch and their impact on soil moisture and yield of chickpea are evaluated in dryland conditions.

Materials & Methods
This experiment was carried out on chickpea (var. ILC481) as a split plot in a randomized complete block design (RCBD) with three replications at the research farm of Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran during 2011-2012. The main plot treatments were moisture retention, including control without mulch, corn, straw mulch (1 kg/m2) wheat straw mulch (1 kg/m2), farmyard manure mulch (3 kg/m2), soil, mulch (using the sweep to cut pipes capillary) and supplemental irrigation at podding stage (to compare with the ideal condition). The sub plots were sowing depth 4, 8 and 12 cm. The annual rainfall was 305.5 mm during the studied year and soil texture was clay. Each plot consists of 6 planting lines with length of 3 meters. Sowing date was done on 16 October 2011. Plant density was 40 plants per square meter with 25 cm between row spacing and 10 cm in the rows. In this work, measured traits were included soil moisture at different growth stages (vegetative stage, flowering, pod and grain filling) at depths of 0-30 and 30-60 cm, grain yield and biomass. In order to estimate soil moisture content, sampling was conducted by auger. Data were analyzed using the SAS and MSTATC softwares and the means were compared using the Duncan test at the 5% level.

Results & Discussion
Results showed that there are significant differences at podding stage (depth 0-30 cm) between different types of mulch and between sowing depth (30-60 cm), different mulching types and also the interaction between mulch and sowing depth. Soil moisture (depth of 30-60 cm) was significant for all treatments (mulching and sowing depths) and for different growth stages, including vegetative growth, flowering, podding and maturity stages. The mulches which could preserve the highest percent of soil moisture were farmyard manure mulch, wheat straw mulch, soil mulch and corn straw mulch, respectively. The lowest soil moisture content (average depths of 0-30 and 30-60 cm) was obtained under no mulch condition and at reproductive phase, flowering, podding and grain filling (8.0, 10.6, 14.1 and 17.4 percent, respectively) and the maximum soil moisture content for farmyard manure mulch were 12.2, 15.1, 17.3 and 19.3 percent, respectively. Sowing depth of 12 cm decreased the more moisture from depth 30-60 cm. Grain yield increased under wheat straw mulch (30%), manure mulch (18%), corn straw mulch (16%), and soil mulch (12%) compared to the control (non-mulching), respectively. Grain yield reduced under wheat straw mulch (31%), manure mulch (37%), corn straw mulch (38%) and soil mulch (40%) compared to supplemental irrigation, respectively.

Conclusion
The results revealed that under mulch treatments the soil moisture trends were slower compared to treatments without mulch. Farmyard manure mulch indicated the highest ability to retain moisture and after that wheat straw and corn stubble mulch demonstrated the highest ability to retain the moisture. Thus, it seems that in areas that there is the possibility of supplementary irrigation, use of these treatments will provide more moisture for plants. Furthermore, a deeper planting seed (12 cm) causes moisture depletion from greater depths. According to the results, it seems that the use of deeper sowing depth and mulching can be an appropriate technique for dryland condition.