Effect Of Organic Fertilier On Nutrition And Growth Of Citrus

Citrus is one of the world’s largest fruit types, and the citrus plantation area and yield in China ranked the first worldwide. In China, citrus plantation area was2.21million hectares which accounted for1/5of the global area, and the yield was26.4million tons which accounted for12%of the global yield in2010. Although the citrus industry has become one of pillar industries in the rurals of main citrus production areas of southern China, the competitiveness was deficient because average yield and quality of citrus in China ranked low. Low yield of citrus in China was attributed to many factors, among which low content of soil organic matter and unreasonable fertilization were two of the major factors. Chongqing is one of the best ecological regions for citrus plantation, but both of the yield and quality of citrus were low. To solve these problems, an extensive farmer survey was conducted to investigate the farmer practice of fertilization in main citrus production area of Chongqing; thereafter a pot experiment and field experiment with varied OF application were also conducted to evaluate the effect of organic fertilizer (OF) application along or together with inorganic fertilizer (IF) on citrus growth, nutrient accumulation, fruit yield and quality, with the aims to provide the theory basis of soil fertility improvement in citrus orchard and fertilization recommendation in Chongqing. The main results were showed as follows:The survey showed that partial application chemical fertlizer and ignored application of organic fertilizer in citrus plantation area in Chongqing resulted in low soil organic content. Overall,56%of citrus grower did not apply OF, and the application of OF was even less on the orchards in large scale. The application rate of OF was quite different among farmers, the nutrient of NPK origined from OF accounted-for13.5%,18.1%and24.9%of the total input nutrient, respectively. The citrus yield increased with the increasing application of organic N and P. The average soi organic matter (SOM) content was15.0g/kg and53.1%of the citrus orchord in Chongqing ranked in low level. SOM content with OF application was9.7%higher than the background samples without OF application. SOM had significant positive correlation with available nutrients in citrus plantation soil and also the citrus yield.The pot experiment showed that OF application was8%of the total soil weight and combined100mg N/kg soil resulted in improved available nutrient in soil and enhanced the shoot growth, development of fine root, the root-shoot ratio, and the nutrient uptake of citrus, and delayed the soil acidification. But excessive application of organic manure and N fertilizer could inhibit the growth of citrus. The results also showed that treatment with manure was better than that with commercial organic fertilizer.The field experiment were conducted with3years and showed that combined application of OF and IF had significantly increased SOM content in soil layer of20～40cm, which was15.9%higher than that with only IF application. With the increase of SOM content and the improvement of soil fertility, the active roots was significantly increased by40%,107%,115%in soil layers of0～20,20～40, and40～60cm, thereby the uptake of nutrients and water by citrus was enhanced and the yield and quality of citrus were also increased. Compared with IF application, combined application of OF and IF increased citrus yield by7.4%, reduced the titratable acid concentration, and also increased the soluble solids content by7.4%and ratio of soluble solid to acid by11.4%.