Effects of calcium fertilizer application on absorption and distribution of nutrients in peanut under salt stress.

In order to solve the problems of nutrient absorption and accumulation and provide theoretical basis for rational amount of calcium fertilization of peanut in saline land, the effects of calcium fertilizer application on absorption and accumulation of nutrients including nitrogen, phosphorus, potassium, calcium and magnesium in peanut under salt stress were examined. Using 'Huayu 25' as experimental material, four Ca levels [T1 (0), T2 (75), T3 (150) and T4 (225) kg·hm-2 CaO] were set under 0.3% salt stress in a pot experiment. The results showed that nutrient contents in peanut followed the order of nitrogen > potassium > calcium > phosphorus > magnesium. At the seedling stage, leaves were the absorption center of nitrogen and calcium, while stems were the center of phosphorus, potassium and magnesium, with nearly half of nutrient accumulation being distributed in the corresponding growth center. At mature stage, the absorption centers of nitrogen, phosphorus and potassium were transferred to pod. The accumulation of nitrogen and phosphorus in seed kernel reached to 72.3%-78.9%. The absorption centers of calcium and magnesium was still in the leaves and stems, with a distribution ratio of 49.8% and 32.6%, respectively. Salt stress significantly inhibited nutrient absorption and distribution in peanut, especially decreased the nitrogen accumulation in leaves and seed kernels. However, salt stress increased the magnesium accumulation in pod. Exogenous calcium application had significant positive effect on absorption and accumulation of nitrogen, phosphorus, calcium and magnesium in different organs of peanut under salt stress. It had significant adjustment on phosphorus accumulation in seed kernel, which was increased by more than 50%. Appropriate calcium content could significantly promote the peanut nutrient absorption and accumulation under salt stress and improve the distribution ratio of nitrogen, phosphorus, potassium in mature pods of peanut. According to the responses of nutrient absorption and distribution, the optimized application amount for calcium fertilizer under 0.3% salt stress was 150 kg·hm-2 CaO.