Studies On Nutrient Distributing Principle And Environmental Effect Under Organic Vegetables Planting System In Protected Field

Recently, organic vegetable industry develops rapidly in China. In some dense organic vegetable production region, for example, Shan dong province and Bei jing city, organic vegetables planting faces some problems because farmers depend on the experience of conventional management including water and fertilization and lack of the theory about water and fertilization and some experimental data. Under organic vegetable planting condition, the reseach studied two irrigation and three fertilizer treatments which influenced yields, quality, soil nutrients and leaching of nitrogen and phosphorus. The results were as follows:When the amount of fertilizer was reduced to two third of conventional fertilizer treatment and amount of irrigation was reduced to 80 percent of conventional irrigation treatment, yields of the last two organic vegetable crops decreased except for the first crop. And nitrate content was reduced by 27.1 percent and 6.3 percent compared with conventional fertilizer and irrigation treatment.The Nmin content accumulated gradually in 0-90 cm soil layer under the planting of three organic vegetable crops. The soil Nmin content of conventional fertilizer treatment were 395.99 kg/ha and 366.58 kg/ha under two kinds of irrigation treatments. But the soil Nmin content decreased significantly when the amount of fertilizer was reduced.Phosphorus accumulated greatly in 0-30cm soil layer because the amount of organic fertilizer was calculated according to the nitrogen application amount and the nitrogen, phosphorus and potassium content of organic fertilizer were unparallel. The soil Olsen-P contents of conventional fertilizer treatment has reached 237.75 mg/kg and 248.34 mg/kg under two kinds of irrigations. Meanwhile, the soil organic matter, total nitrogen and total phosphorus content have increased partly.Amount of fertilizer and irrigation affected the leaching dramatically. When amount of irrigation was reduced to 80 percent of conventional amount, the loss of leachate, nitrogen and phosphorus were reduced by 31.4%,47.0% and 65.4%. When the amount of fertilizer was reduced to two third of conventional amount of fertilizer, the loss of leachate, nitrogen and phosphorus were reduced by 22.2%,29.5% and 52.5%.The conventional fertilizer treatment was higher than the other fertilizer treatment when we calculated nitrogen, phosphorus and potassium surplus. The phosphorus surplus of conventional fertilizer treatment has reached 4398.6 kg/ha and 4387.75 kg/ha under two kinds of irrigation treatments. Meanwhile, potassium use efficiency was higher than that of nitrogen and phosphorus and the irrigation use efficiency of conventional irrigation treatment was lowerer than the other treatment that amount of irrigation was reduced to 80 percent of conventional irrigation treatment.