The Establishment and Validation of Critical Nitrogen Concentration Dilution Curve of Garlic Based on Leaf Area Index

Abstract

Irrational application of nitrogen fertilizer will increase the risk of environmental pollution, reduce crop yield and nitrogen use efficiency. Plant nitrogen diagnostic method can be used to improve nitrogen management in garlic cultivation. In this research, two representative garlic (Allium sativum L.) cultivars Cangshan and Gailiang in Guanzhong area were used as test materials for a two-year field experiment. The critical nitrogen concentration (Nc) dilution curve models was constructed and verified by analyzing the effects of six nitrogen application levels (0, 65, 130, 195, 260, 325 kg·ha−1) on leaf area index (LAI) and nitrogen concentration from regreening stage to late stage of garlic bolting. The results indicated that the relationship between Nc and LAI can be expressed by power function equation, Cangshan: Nc = 4.44LAI−0.51, Gailiang: Nc = 3.91LAI−0.4. Nitrogen nutrition index (NNI) increased with the rising of nitrogen level; meanwhile, the integrated NNI was closely related to relative yield. The maximum yield was obtained and the nitrogen nutrient index was close to 1 when the nitrogen level reached 195 kg·ha−1 in Cangshan and 260 kg·ha−1 in Gailiang, respectively. In general, Nc dilution curves depending on LAI can be used for precision nitrogen management of garlic in Guanzhong area.