Study On Nutrient Balance Of Five Agro-Ecosystems In Jurong

Based on the investigation on the 30 years fertilization of five agro-ecosystems in Jurong by visiting farmers and field reseach, the input and output of N, P, K, and nutrient balance were analyzed.The results showed: in the rice-rape, rice-wheat agro-ecosystems, the input of fertilizer was shifted from organic manure to inorganic fertilizer, which resulted the profit of N, P. But the profit of N, P progressively declined. The profit of K became the deficit later. In comparison with these systems, the rice-duck-rape system improved the nutrient balance, which showed lower N, P profit and less K deficit.In the rice-green house strawberry agro-ecosystem, the most of input was from the organic manure. The N, P, K input from organic manure was 80.01%, 57.65% and 55.50% of total input. The ratio of N:P:K was 1:0.28:0.70 and was rational. The profit of N, P, K was 34.27%, 264.47% and 33.12%.In sweet potato-rape agro-ecosystem, the input of N, K from inorganic fertilizer increased but the ratio of inorganic N, P, K was unbalanced. Because the input of organic manure decreased. N and P profit was significantly high, but the K profit became deficit later. The recycle rate of nitrigon accelerated every year. The recycle rate of P, K decreased and then increased without significant difference.In conclusion, the following measurements should be taken up:In rice-rape, rice-wheat, sweet potato-rape agro-ecosystems, application of organic manure and K should be improved but the input of N should be in control.In rice-duck-rape agro-ecosystem, application of K is the most important, and N and P should be in control. And input of organic manure should also be properly increased.In rice-green house strawberry agro-ecosystem, the application of organic manure should be kept on, but the input of P should be cut down.