The Effect of Nitrogen Fertilizer and Planting Pattern on Yield and Competition Indices of Pea (Pisum sativum L.) and Lettuce (Lactuca sativa L.)

  Intercropping, the agricultural practice of cultivating two or more crops in the same space at the same time, is an old and commonly used cropping practice which aims to match efficiently crop demands to the available growth resources. Intercropping of chickpea with linseed reduced the chickpea yield by 60.3%, although linseed occupied only 33% of the total area. The loss of chickpea yield was compensated by the additional yield of linseed, and thus the system productivity of chickpea + linseed intercropping was increased by 43.4% compared to the sole chickpea. Of this increase in system productivity, 65.3 and 34.7% were contributed by higher seed yield and higher minimum support prices of linseed, respectively, as compared to chickpea. The objectives of the present study were to study the competition indices of Pea and Lettuce intercropping, such as land equivalent ratio, relative crowding coefficient, aggressivity, pea equivalent yield and effects of nitrogen and different intercropping arrangements on the yield of sole pea, sole lettuce and intercropping yield of two plants. In order to study the effect of planting pattern and nitrogen application on yield and competitive indicators of pea and lettuce, a factorial experiment based on Randomized Complete Block Design was conducted with three replications at research farm of Gonbad Kavous University during the growing season of 2014-2015. The treatments of the planting pattern were included 9 levels of sole pea, 67% pea + 33% lettuce, 50% pea + 50% lettuce, 33% pea + 67% lettuce, 100% pea + 33% lettuce, 100% pea + 50 % lettuce, 100% pea + 67% lettuce, 100% pea + 100% lettuce and sole lettuce and the nitrogen factor was included three levels of non-application and application of 25 and 50 kg N.ha-1. Row spacing was 30cm. Density of pea and lettuce was 33.3 and 16.7 plants.m-2, respectively. The results showed that the effect of planting pattern and nitrogen application on the yield was significant on the confidence level of 99%. Additive treatment of 100% lettuce + 100% pea and lettuce sole cropping with 61565 and 61473 kg.ha-1 were produced the maximum yields and pea sole cropping with 11759 kg.ha-1 produced the minimum yield. Total yield was increased with increasing nitrogen fertilizer application. The maximum and minimum equivalent yield was achieved in additive treatment of 100% lettuce + 100% pea and sole cropping of pea, respectively. The most and the least pea equivalent yield were obtained from treatments of 50 kg nitrogen/ha and non-application of nitrogen with 20669 and 16689 kg.ha-1, respectively. Land equivalent ratio in intercropping treatments was greater than sole cropping. The maximum land equivalent ratio with 1.48 belonged to additive intercropping of 100% pea + 100% lettuce. Therefore, intercropping of pea and lettuce, especially in additive series was appropriate. Relative crowding coefficient in all traits was more than 1. Aggressivity index showed that pea in additive treatments and replacement of 33% lettuce instead of pea was the dominant plant. Increasing of actual yield was observed in all treatments, especially in additive series. Intercropping advantage and system productivity index in all treatments of additive and replacement treatments was greater than 1, therefore Intercropping had sufficient economic benefits in this mixture. Of the two plants of pea and lettuce, lettuce produced more yield than pea in all treatments. Additive treatment of 100% lettuce to pea and lettuce sole crop with 61565 and 61473 kg.ha-1 produced the maximum yield and pea sole crop with 11759 kg.ha-1 produced the minimum total yield. With increasing of nitrogen fertilizer consumption, yield was increased. According to the results, it seems that obtaining the maximum yield in the intercropping system required increasing plant density