Nutrient Budget and Soil Nutrient Status in Greenhouse System

This paper is based on nutrient budget and its effects on soil nutrient status in typical greenhouse system in China to provide a basis for raising the utilization rate of fertilizers and maintaining the sustainable development of agriculture in the greenhouse.By investigating the management of 18 representative greenhouses in Shouguang,Shandong Province,China,and analyzing both the greenhouse and open field soil samples,the soil nutrient budget and the trend of nutrient accumulation and translocation in soils were thus studied.The results under greenhouse system showed that the average annual inputs of N,P2O5 and K2O were 4 088,3 655 and 3 437 kg ha-1,respectively.The total inputs of N,P2O5 and K2O provided by chemical fertilizers which are the main source of soil nutrient were 63,61 and 66%,respectively.The utilization rates of N,P2O5 and K2O were only 24,8,46% and the input ratio among N,P2O5 and K2O （1：0.9：0.8） was quite different from the uptake ratio （1：0.3：1.4）.It had caused the excess of N,P2O5 and K2O in the soil,and the theoretical surpluses were 3 214,3 401 and 2 322 kg ha-1,respectively,for N,P2O5 and K2O.The level of the organic matter,total nitrogen,nitrate nitrogen,available phosphorus,and available potassium was increased substantially,and their maximum level was observed in the topsoil （0-20 cm） with an average value being 1.4,1.9,21.2,5.4,and 3.7 times higher than that of the open field soil,respectively.The greenhouse soils showed leaching of the nutrients,especially NO3- which would cause a potential risk to the quality of groundwater in the area.It is necessary to apply more organic manure and provide nutrients according to the crop requirements and soil fertility as it could not only produce high crop yield,but also be beneficial to balance the soil nutrient and improve the utilization rate of fertilizers.Further,there would be no significant surplus of nutrients which may leach out of soil to contaminate the environment.

Optimum nitrogen fertilization of Calophyllum inophyllum seedlings under greenhouse conditions

A greenhouse pot experiment was conducted to study the effects of nitrogen fertilization on Calophyllum inophyllum seedlings grown with 0, 50, 100, 150,200, 300, 400 and 600 mg N per seedling according to exponential functions. Seedling height, root collar diameter, leaf area and total biomass increased with increasing fertilization from 0 to 200 mg N per seedling and decreased with further increase in fertilization from300 to 600 mg N per seedling. The net photosynthetic rate,stomatal conductance, intercellular CO_2 concentration and transpiration rate of C. inophyllum seedlings showed a unimodal parabolic trend, with peak values of7.29 mmol·m^(–2)·s^(–1), 0.071 mol·m^(–2)·s^(–1), 220 mmol·mol^(–1) and 1.34 mmol·m^(–2)·s^(–1), respectively, when the rate of fertilization was 200 mg N per seedling. Photosynthetic gas exchange parameters were significantly different among nitrogen treatments. Based on the critical values of leaf N and P concentration and N/P ratio, the optimum amount of nitrogen of C. inophyllum seedlings was 200–400 mg per seedling for leaf N and P concentration, and100–400 mg per seedling for N/P ratio. It was concluded that 200–400 mg N per seedling was the most suitable nitrogen range for C. inophyllum seedlings.