Effects of N, P, K fertilizer combined application on physiological characteristics, yield and kernel quality of peanut

Applying fertilizer rationally on crop is an effective measure to increase yield and improve quality. Nitrogen (N), phosphorus (P), and potassium (K), associated with the yield formation and quality improvement in peanut, are the nutrient elements with more need in peanut growth and development. To investigate the effects of N, P, and K fertilizer combined application on physiological responses, seed weight, and kernel quality of peanut (Arachis hypogea), five treatments N0P0 K0(CK), N300 P150 (N+P), N300 K300 (N+K), P150 K300 (P+K), P150 K300 (N+P+K) (the data after N, P and K indicate application kilogram numbers of N, P2O5 and K2O per hectare) were designed by furrow applying at seedling stage in peanut variety Fenghua No. 1 in the Experimental Station at the Shandong Agricultural University in 2004 and 2005 with randomized complete block design and three replication. Nitrogen, P, and K combined application increased chlorophyll content and photosynthetic rate in peanut leaves, to a greater extent at middle-later stage (pod filling stage) than at the middle stage (pod setting stage). Peanut treated with N+P+K and P+K had more chlorophyll and higher photosynthesis rate, when compared to N + P and N + K treatments. Nitrogen, P, and K combined application enhanced the activities of superoxide dismutase(SOD), peroxidase (POD) and catlase (CAT) and the content of soluble protein, but reduced malondialdeyde (MDA) content in peanut leaves, to greater extent in N+P+K and P+K treatments than N+P and N+K treatments. Nitrogen, P, and K combined application led to the highest pod and kernel weight, followed by P+K treatment and by N+K treatment. Peanut subjected to N+P+K and P+K treatments had an increased kernel rate. The fat and protein content were improved in peanut kernel treated with N+P+K and P+K. Peanut subjected to N+K treatment had a higher fat content. Fat and protein in peanut kernel were not influenced by N+P treatment. Peanut treated with N+P+K had an increased ratio of oleic acid to linoleic acid (O/L) and the soluble sugar content in kernel.