Research On The Nutrient Diagnosis And Fertilization Of Three Navel Orange Cultivars In Zigui,Hubei Province

Under the high density planting condition of navel orange orchards, the unreasonable fertilizer methods led to the nutrients disorder seriously in the old age navel orange trees in Zigui, Hubei Province of China,. Such nutrients disorder problem limited the yield increasing and the quality improving. A field trials with three navel orange cultivars,'Newhal;'(C. sinensis L. cv. Newhall),'Robertson'(C. sinensis osbeck cv. Robertson) and 'Cara cara'(C. sinensis osbeck cv. Cara cara), grafted on trifoliate orange [Poncirus trifoliata (L.) Raf.], were conducted in three consecutive years. The study focused on the research (1) The characteristics of nutrients dynamic requirement of the leaf in various cultivars navel orange;(2) the effects of applying different ratio of NPK rates on the leaf NPK concentrations and their ratio, respectively;(3) the effects of applying different fertilizer on the soil nutrient status of navel orange orchard;(4) the relationship in leaf nutrient concentration, fruit yield and the NPK quantity of fruit removal;(5) the effects of applying different level of NPK fertilizers on the fruit yield and the quality;(6) determined the recommended fertilizer rate with three Navel orange cultivars by the quantity of fruit NPK nutrient removal. According to the research results, we invented a kind of formula fertilizer which have been applied to the orchards with1000mu, and increased the yield obviously.The main results were as following:(1) Effects of applying different level of NPK fertilizers on the fruit yield and the qualityApplying different levels of NPK rates can increase the fruit yield of Newhall, Robertson and Cara cara navel orange. And applying different micro-nutrients and meso-nutrients fertilizers had the less effect on increasing fruit yield. Newhall in the fertilizer treatment of N2P1K1, Robertson navel orange in N2P3K2and N2P2K3and Cara cara in the N2P1K1had the optimum performance in fruit increasing. This result consisted with the result of the cluster analysis in fruit quality. Newhall in the fertilizer treatment of N2P1K1, Robertson navel orange in N2P2K3and Cara cara in the N2P1K1had the optimum performance in fruit quality. According the results of fertilizer effects, the optimum fertilizer rates were N:80kg/667m2, P2O5:20kg/667m2, K2O:25kg/667m2 in Newhall and Cara cara orchards, and N:80kg/667m2, P2O5:40kg/667m2, K2O:75kg/667m2in Robertson orchards in Zigui, Hubei Province.(2) Determination of the NPK recommended fertilizer rates by the quantity of fruit NPK nutrient removalAnalysis of the fruit NPK concentration in Newhall, Robertson and Cara cara navel orange, the results showed the fruit NPK concentrations were less affected by different NPK fertilization levels in the same navel orange cultivar, and obviously in various cultivars. The recommended fertilizer rate can be identified by the quantities of fruit NPK removal. Accordingly, the basic rates of recommended fertilizer were N:34.03-56.72kg/667m2, P2O5:13.82-21.80kg/667m2, K2O:26.34-37.92kg/667m2, N:P2O5: K2O=14:5:10in Newhall, N:37.27-62.11kg/667m2, P2O5:15.61-24.62kg/667m2, K2O:27.79-40.01kg/667m2, N:P2O5:K2O14:6:10in Robertson and N:45.51-75.85kg/667m2, P2O5:17.00-26.82kg/667m2, K2O:37.05-53.36kg/667m2, N:P2O5:K2O=14:5:10in Cara cara.(3) The nutrients dynamic requirement of the leaf in various cultivars navel orangeDifferent leaf nutrient-elements were difference in the nutrients dynamic requirement, and the same nutrient-element in various cultivars navel orange had the similar dynamics variation characteristic in the same year, and the same nutrient-element were difference in the similar dynamics variation characteristic in various years. The nutrients dynamic changes were lower from early September to later September and higher in other period. Generally, leaf N in the navel orange tree had the increasing tendency from the beginning of March, and reached the accumulative peak at August, and then decreased. P decreased from March, and then increased from May, and reached the peak at August. K decreased from March, and then increased from May, and reached the peak at August. Leaf Ca concentration increased with the leaf age. Mg increased from March, and reached the first peak at May, and then decreased, and increased form August, and reached the second peak at September. Fe and Mn increased from March, and reached the first peak at May, and then decreased, and increased form August, and reached the second peak at September. The dynamic of Cu were different in various years. Zn increased from may, and kept the high level from May to August. (4) Effects of applying fertilizers on the trees nutrients status and the characteristic of tree nutrients requirementApplying different fertilizers in the first year had less effects on trees, and higher in the second and third year with the application of fertilizer. Comparing with2008, The leaf NPK nutrients increased in2009and2010. Applying N with middle or high levels of NP fertilizers, the leaf N and P concentration in the three navel orange cultivars in September were in the optimum ranges or higher the ranges. Leaf K concentration in Newhall navel orange was in the optimum range, while Robertson and Cara cara were below the optimum range. The three navel orange cultivars showed the similar results in leaf micro-element concentrations in September, which were all in optimum range, or higher the ranges, with the exception of leaf Zn in Newhall and Robertson (below the range).The effects of applying various levels of NPK on leaf NPK concentrations were different in stages of navel orange tree grown up, which indicated the sensibility of applying NPK fertilizers on tree could be affected by the quantity of nutrient requirement, the nutrients storage in tree and the application of NPK fertilizers.Leaf N was sensitive to NPK fertilizer application at May and August in Newhall, and at August and September in Robertson, and at August and September in Cara cara. Leaf P was sensitive to NPK fertilizer application at May and August in Newhall, and at August and September in Robertson, and at August and September in Cara cara. Leaf K was sensitive to NPK fertilizer application at May and September in Newhall, and at March and May in Robertson, and at March and May in Cara cara.Analyzed the NPK ratios of leaf in applying different levels of NPK, the ratios of N/P, N/K and K/P had the high range of variability than the leaf N, P and K in various stage of tree grown up. Leaf N/P was sensitive to NPK fertilizer application at August in Newhall, and at August in Robertson, and at May and August in Cara cara. Leaf N/K was sensitive to NPK fertilizer application at August and September in Newhall, and at March, May and August in Robertson, and at May and August in Cara cara. Leaf K/P was sensitive to NPK fertilizer application at August in Newhall, and at August in Robertson, and at September in Cara cara. Leaf Mg was sensitive at March in Newhall, and at September in Robertson, and at August in Cara cara. Leaf Fe was sensitive at May in Newhall and Robertson, and at May in Cara cara. Leaf Mn and Zn were sensitive at May in Newhall, Robertson and Cara cara.(5) Effects of applying different fertilizer on the soil nutrient status of navel orange orchardThe soil nutrient status of the orchards of Newhall and Robertson were mainly in the properties:pH was at the low level, and the available nutrients of N, P, K, Ca, Mg, Cu were all at the optimum or high level, and the avail-Fe and avail-Mn at the excessive level, and avail-Zn the deficient level in the study area of Zigui, Hubei Province. The soil nutrient status of the orchards of Cara cara was the same as the Newhall and Robertson, with the exception of avail-Zn which was at optimum level. We draw the conclusion that the low pH and the deficiency of Zn was the main nutrient limiting factors in the navel orange orchards of Zigui, Hubei Province.(6) Navel orange orchard nutrient balance analysisThe study showed that leaf nutrient concentrations were less different in high and low yield navel orange trees, especially in leaf NPK concentration. The coefficient of variation of the leaf NPK nutrient ratios were less in the high yield trees than the low, which indicated that the single leaf nutrient concentration was not the main nutrient limiting factor for citrus yield and leaf nutrient reached a certain range of balance was the main factor for navel orange yield increasing.(7) Application of the special formula fertilizerThe commercial fertilizer for Zigui, Hubei Province were (1) the formula N-P2O5-K2O=14-7-9(contained8%humic acid,1%zinc and0.5%boron),200-250kg/667m2, applied in mid March;(2) the formula N-P2O5-K2O=12-8-10(contained8%humic acid fertilizer, and0.5%boron)150-200kg/667m2, applied in late May or early June.Compared with the local conventional fertilization, the application of the commercial fertilizer increased the yield23.04%in Newhall navel orange,21.14%in Robertson and15.38%in Cara cara. And the average yield reached4680kg/667m2,5980kg/kg/667m2and5405kg/667m2. The commercial fertilizer improved the soluble solids and Vc content in Newhall fruit, and maintained the original quality of Robertson and Cara cara. And the increase economic benefits were1000-1500yuan/667m2.