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

Evaluation of a model recommended for N fertilizer application in irrigated rice

The response of rice to N fertilizer applicationhas shown that high rates of N application donot always ensure a proportional increase inyield due to high N losses. A model, ORYZA-0 was developed by ten Berge for designingoptimum N fertilizer management strategy inrice. We evaluated the performance ofORYZA-0 in Jinhua, Zhejiang Province. ORYZA-0 includes N uptakes, partition-ing of N among the organs, and utilization ofleaf N in converting solar energy to dry mat-ter. It can predict the amount and time of Nfertilizer application to achieve a maximumbiomass or yield combining with Price algo-rithm optimization procedure.

Effects of Interaction of Soil Moisture and Organic Matter on Powdery Mildew Disease and Growth of Heracleum moellendorffii Hance

Taking annual Heracl'eum moellendorffii Hance as the material,this research studied the epidemic dynamics of H.moellendorffii Hance powdery mildew and plant growth by using the interactive methods of soil moisture and soil organic matter.The results showed that the interaction of higher soil moisture content(60%-80%)and soil organic matter content(75-100 g•kg^(-1))had few diseases,dosease index and area under disease progression curve(AUDPC)compared with those of other treatments,thus could effectivley control powdery mildew disease.Moreover,higher soil moisture and organic matter content increased the yield,contents of soluble sugar,soluble protein,vitamin C and coumarin in H.moellendorffii Hance.