An Analysis of Cassava Yield Gap and Its Limiting Factorsin in the Main Producing Areas of Guangdong Province
In order to analyze the limiting factors in the the cassava yield gap in the main producing areas of Guangdong Province,and search for ways to reduce the yield gap,the cultivation management of farmers were investigated in this study,also the levels of yield gap and its limiting factors were analyzed from the as-pects of group construction,nutrient management and production and investment structure. The results showed that cassava yields were significantly different among different yield levels,and the yield gap YGTbased on the high-yield farmer's yield ,the yield gap YGBin the high yield record,and the modeled yield gap YGM were 14. 32,39.05, and 42.86 t/hm2,respectively.In the group construction of cassava,the average planting density and continuous cropping years of 25％ of the lowest yield farmers were significantly higher than those of other farm-ers.In terms of nutrient management,the proportion of N in fertilizer was too high,P2O5 and K2O amount were insufficient in 25％ of the lowest yield and 25％ of the medium yield farmers,in particular,the amount of K2O and its ratio were extremely low.N,P2O5 and K2O amount for basic fertilization were far lower than those of other farmers,N amount was higher and K2O amount were lower for top-dressing fertilization.Under the current management level,the contribution rates of N,P 2 O5 ,K2O to the yield gap were 23.1％,22.2％ and 34.4％,re-spectively,only 6.02％～10.11％of the farmers reached a high yield and high efficiency. In the composition of production and investment structure, the ratio of yield to investment was at the maximum when the yield reached 72.71 t/hm2 ,after that,it showed a diminishing tendency with the increasing of yield. The cost of la-bor,especially that spent on the harvest,was the main limiting factor in yield.Based on these findings,it is pro-posed that reasonable density,reduction of continuous cropping years,increase in nitrogen,phosphate and po-tassium fertilizer for basic fertilization,reduction in nitrogen fertilizer and increase in potassium fertilizer for top-dressing fertilization,promotion of full mechanization are important ways to reduce the yield gap of cassava.
cassavaGuangdong Provinceyield gapcontinuous croppingplanting densityfertilizationproduction and investment structure
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