Effects of Supplemental Irrigation on Water and Nitrogen Use, Yield, and Kernel Quality of Peanut under Nitrogen-Supplied Conditions

Abstract

Improving both nitrogen utilization and peanut kernel quality (after removing peanuts shell) through water management is a growing concern for farmers. To explore the role of supplemental irrigation in nitrogen transformation between ‘source’ and ‘sink’, a split-plot experiment was conducted to evaluate the effects of water (rain-fed irrigation as IRI; supplemental irrigation as ISI) and nitrogen (0 kg∙ha―1 as N0; 40 kg∙ha―1 as N1; 60 kg∙ha―1 as N2 and 80 kg∙ha―1 as N3) coupling on soil nitrate nitrogen content, nitrogen accumulation and kernel quality of peanuts. We determined the dry matter weight per plant at peanut maturity as 64.66—74.92 g and 71.65—92.81 g for IRIN0 and ISIN3, respectively. ISIN2 significantly increased nitrogen accumulation, yield and water productivity. Furthermore, the ISI treatment prolonged the nitrogen uptake accumulation time of leaves, thus enhancing the nitrogen transfer from the leaves to the pods. Thus, the ISI treatment significantly increased the nitrogen harvest index by 2.13% and the nitrogen agronomic efficiency by 78.57% compared to the IRI treatment. In addition, the essential amino acid content in the fruits was within the range of 5.57—6.08%, while the content of non-essential amino acids was 16.43 to 17.46%. N1 was able to significantly increase the content of non-essential and essential amino acids, while ISI reduced the content of essential amino acids. Post-harvest soil nitrate nitrogen was principally distributed in the 0—40 cm soil layer, accounting for 77.75% of the 0—60 cm soil layer. Although the supplemental irrigation is associated with an increased risk of the nitrogen moving deeper into the soil, it greatly enhances nitrogen transfer from leaves to the pods at nitrogen application rates of 40—60 kg ha―1.