Effect of Green Manure under Different Conditions of Tillage on Weed Characteristics and Corn (Zea mays L.) Yield

High degree of evaporation from soil surface (due to high temperature of environment and low relative humidity), poor soil organic content and instability of soil structure are considered indicators of arid regions of Iran. It seems that in a regional management, conservation of plant residues with irrigation operations in the absence of a negative effect on yield can be used as a way to improve the above-mentioned conditions. The management of plant residues has been interesting to researchers in recent decades due to its various effects on the physical, chemical and biological properties of soil. On the other hand, protective tillage can help to maintain more soil moisture, reduce erosion and less use of agricultural machinery, thereby achieving sustainable agriculture and reducing costs. This research was conducted to investigate the effect of application of wheat residues and green manure along with different tillage systems on corn.

This experiment was conducted in Shush, Khuzestan Province in 2015-2016, as strip-plot in randomized complete block design with three replications. The main treatment consisted of conventional and minimum tillage methods. The sub-plot treatment applied mulches such as wheat residue, two types of green manure (mung bean (Vigna radiata L.) and cowpea (Vigna unguiculata L.)) and control (no fertilizer application). The characteristics in this research included grain yield, biological yield, number of rows in corn, number of kernels per row, 100 grains weight, and weed growth indices (density, variety and dry weight in two stages: 4 to 6 leaf and maturity of corn).

Results

Maximum grain yield of corn was obtained in wheat residue (10399.27 kg ha-1). Also, there was no significant difference in plants treated with green manure of cowpea (10013.49 kg ha-1). The lowest economic yield was seen in control (7382 kg ha-1). Similar to grain yield, the highest biological yield of corn occurred with application of minimum tillage (16139.14 kg ha-1), wheat residue (17170.89) and cowpea green manure (16790.37 kg ha-1). Besides, the best treatment to reduce the number, variety and dry weight of weeds, was achieved with green manure in minimum tillage. Based on the results, the dominant weed of the field in conventional tillage in 4 to 6 leaf stage was physalis (Physalis alkekengi) while it was common purslane (Portulaca oleracea) in the minimum tillage. In maturation of corn, both in conventional tillage and minimum tillage, the dominant weed was physalis, which had the highest dry weight of weeds in every stage.

Based on the results of this research, application of wheat residues and cowpea green manure combined with minimum tillage can be a suitable way to increase corn yield and reduce weed diversity and biomass in sustainable agriculture.