Effects of Different Drip Irrigation Fertilizers on Nutrient Levels in Celery and Soil under Drip Irrigation

This study was conducted to investigate the effects of different fertilizers on nitrogen, phosphorus and potassium ＇absorption and distribution by celeo, and the changes of soil nutrients in the 0 -40 cm soil layer under drip irrigation, so as to provide a theoretical basis for nutrient management of greenhouse celery culti- vation and special fertilizer development. With celery as an experiment material and the ratio of conventional fertilization as control treatment, the effects of different ratios of nitrogen, phosphorus and potassium on nutrient absorption by celery and changes of soil nutrients were investigated by plot experiment in greenhouse. The results showed that the contents and distribution proportions of N and P in leaf were higher than those in stem, while for K, the content and distribution proportion were higher in stem than in leaf. The absorption amount of K was the highest in celery, followed by N, and the absorption amount of P element was the least. The mean ratio of N, P and K in celery was 1：0.556： 1.609. There were evident dynamic changes in contents of soil available nutrients in the 0 -20 cm soil layer in various growth stages of celery under different drip irrigation fertilizers. The contents of soil available nutrients were higher on the 28＇h , 47~ and 83＇h d ＂after fieht planting, while those before field planting and after harvest were lower. So the amounts of soil available nutrients were closely related to the growth stage of celery. In the whole growth period of celery, the mean input amounts of N, P205 and K20 were 805, 1 049 and 916 kg/hm2 , respectively, but the absorption amounts of nutrients by celery were far less than inputs, and the amounts of N, P205 and K20 absorbed by celery＂ were only 23% -26% , 10% and 31% -35% of the appli- cation amounts, respectively. The apparent balance of N, P2 O5 and Kz O were 613,943 and 609 kg/hm2 , respectively, indicating excess fertilization in this experi- ment. Under this experiment condition, Tj （ N： PzOs： K20 = 1 ： 0.63： 1.08） favored increase of celery yield and absorption of nitrogen, phosphorus and petassium by celery. The results will provide a scientific basis for study and utilization of special fertilizer for drip irrigation on celery. Key words Drip irrigation; Fertilizer for drip irrigation; Celery; Soil nutrient; Apparent balance

Selection and Design of WSN Node Based on Solar Power in Facility Greenhouse

In this study, the green energy saving of greenhouse sensor node is de- signed to reduce the system power consumption and high efficiency. The green renewable solar energy resources are used as the energy source of nodes; the lowenergy consumed and cost effective MSP430 chip is used as the main control chip of the processor unit; the transmission frequency of the wireless transmission unit is 433 MHz, which has the characteristics of low power consumption, high signal strength, long transmission distance and small signal attenuation during the transmission; the power supply system unit is composed of monocrystalline silicon solar panel and high performance rechargeable lithium ion battery. The selection basis of each unit is clarified in detail, and optimization is performed by hardware circuit and software program to further reduce power consumption. The power consumption of the node is calculated by the experiment, and the charging conditions of the solar panel used in the node is tested. The results show that the system can achieve the setting target through the selection and design.

Groundwater Nitrate Contamination and Driving Forces from Intensive Cropland in the North China Plain

High nitrate in groundwater is a serious problem especially in highly active agricultural areas.In this paper,the concentration and spatial distribution of groundwater nitrate in cropland area in the North China Plain were assessed by statistical and geostatistical techniques.Nitrate concentration in groundwater reached a maximum of 526.58 mg/L,and 47.2%,21.33%and 11.13%of samples had levels in excess of nitrate safety threshold concentration(50 mg/L)in shallow,middle-deep and deep groundwater,respectively.And NO-3 content significantly decreased with groundwater depth.Groundwater nitrate concentrations under vegetable area are significantly higher than ones under grain and orchard.And there are great differences in spatial distribution of nitrate in the North China Plain and pollution hotspot areas are mainly in Shandong Province.Based on both multiple regressions combined with principal component analysis(PCA),significant variables for nitrate variation in three types of ground water were found:population per unit area,percentage of vegetable area,percentage of grain crop area,livestock per unit area,annual precipitation and annual mean temperature for shallow groundwater;population per unit area and percentage of vegetable area for middle-deep groundwater;percentage of vegetable area,percentage of grain crop area and livestock per unit area for deep groundwater.