Elimination of Irrigation Restriction in Spring Corn(Zea mays) Planting by Relay-Intercropping with Canola(Brassica napus L.)

IntroductionWater shortage in spring for the cultivation of summer crops is a challenge for farmers in most parts of the country due to the fact that cultivation of these crops coincides with the one or two last irrigations needed for cereals during the critical stage of grain filling. Corn, sugar beet, and other summer crops are cultivated during such periods, and hence water allocation is normally problematic during this period. Relay cropping has been considered as a method to overcome such problems. Furthermore, overseeding of one crop to the stand of another crop in the last stage of development of the second crop (relay intercropping) has been considered as energy-saving and efficient resource use method. The aim of the present work was to investigate the possibility of relay intercropping of corn and canola in order to save water and hence overcome water shortage effects in early spring for summer crops.Materials and MethodsIn order to evaluate the possibility of relay intercropping of corn and canola, an experiment was conducted 10 kilometers west of Shirvan in two growing seasons of 2012-13 and 2013-14. The experiment was conducted as a randomized complete block design with six treatments and three replications. Treatments included four relay sowing rates of canola and corn (3 rows of canola: 1-row corn, three rows canola: 2-row corn, four rows canola: 2-row corn, six rows canola: 2-row corn), pure stands of canola and corn. Corn seeds were planted between canola rows at the end of the canola growth period to use the latest irrigation of canola for corn germination and emergence. A drip irrigation system was installed, and the amount of water used was measured. All field management operations, including irrigation, fertilizer application, and others, were practiced as the conventional farmers normally conduct. After crop ripening, necessary samples were taken, and finally, LER was calculated for comparison of the treatments.Results and discussionAnalysis Variance of the data showed that the highest 1000-seed weight of canola (3.63 gr) and corn (221.69 gr) were obtained in 4:2 and 3:1 treatments, respectively. This was 3.35 gr for the pure stand of canola and 218.5 gr for the pure stand of corn. Economic and biological yields for both crops of canola and corn were highest in pure stands (2502.5, 9763.5 kg/ha for canola and 6207.6, 15769.2 kg/ha for corn, respectively). The highest seed yield of corn was obtained in 2-row corn and 3-row wheat, but i