Effect of nitrogen application to intercrops on yield, competition, nutrient use efficiency and economics in potato (Solanum Tuberosum L.) + French bean (Phaseolus Vulgaris L.)  system in north-western hills of India

The present study was carried out at Central Potato Research Institute, Shimla for three years to work out the nitrogen requirement of french bean and competition in potato + french bean (1:1) intercropping system. Application of 100% N to French bean, gave 29% higher pod yield than sole cropping, on area basis, however, the mean yield of french bean pods with 100% N was statistically at par with that under 50% N and significantly higher over 0 or 25% N. Land Equivalent Ratio (LER) values were >1 at all N levels to French bean, the highest being 1.296 with 100% of N to french bean. The relative crowding coefficient (RCC) values of both the crops were more than one indicating that both the crops produced greater than ‘expected’ yields under intercropping, however, the aggressivity values indicated that french bean was a dominant species whereas potato was dominated species in intercropping, irrespective of N dose to french bean i.e. the extent of proportionate yield increase of french bean was more than potato in intercropping. The competition ratio also showed that french bean was more competitive than potato when fertilized properly. There was a positive mean balance of NPK and 36-68% of applied N, 64-74% of applied P and 44-77% of applied K was left as residual fertility under various intercropping treatments. Intercropping also gave higher net returns (Rs. 69 to 82 thousand/ha) and benefit:-cost ratio (2.43 to 2.66) than sole cropping of either of the crop. It can be concluded from the study that in potato + French bean (1:1) intercropping in north- western hills, N dose to french bean can be reduced by 50% without impairing soil health in terms of NPK balance.