Utilization and transfer of nitrogen (N) in a strip intercropping system of garlic (Allium sativum L.) and broad bean (Vicia faba L.) have been investigated rarely.  The objectives of this study were to quantify N uptake and utilization by intercropped broad bean and garlic and determine the magnitude of N transfer from broad bean to garlic.  Field and pot trials were carried out in the Erhai Lake Basin in China using ¹⁵N tracer applied to the soil or injected into broad bean plants.  Strip intercropping of garlic and broad bean increased N absorption (47.2%) compared with sole crop broad bean (31.9%) or sole crop garlic (40.7%) and reduced soil residual N.  Nearly 15% of ¹⁵N injected into petioles of broad bean intercropped with garlic was recovered in garlic at harvest, suggesting that N could be transferred from broad bean to strip intercropped garlic.  The findings provide a basis for evaluating legumes’ role in optimizing N fertilization when intercropped with non-legumes.

This study was designed to find out an optimised planting system of reducing non-point (source) pollution by analyzing the reasons and the factors of influence non-point pollution in farmland of Erhai Lake basin. The results showed that incomes, residual nitrogen in soil, and the loss of nitrogen in surface water in rice-garlic system were higher than those in rice-fava bean system. There were positive correlations between the nitrogen loss of farmland, nitrogen inputs, residual nitrogen in soil, and incomes of farmland. Economic benefits and environment benefits are both appropriate, if the area of rice-garlic system would be reduced to 53% and the area of rice-fava bean system increased to 36% of total cropping area in the investigated watershed. Adjustment of planting structure and introduction of reasonable rotation systems is considered an effective measure of controlling agricultural non-point pollution in watersheds of Erhai Lake.