Evaluation of current fertilization status in kiwifruit orchards on the northern slope of Qinling Mountains: A case study of Yujiahe catchment, in Zhouzhi County

【Objectives】 The northern slope region of the Qinling Mountains is suitable for kiwifruit (Actinidia deliciosa) cultivation, and now has developed large area of Kiwi orchards in Shaanxi Province. Therefore, investigating the current nutrient inputs and the problems in kiwifruit orchards is of great significance for increasing fruit quality, generating farmers’ income and promoting industrial development in this region.【Methods】 The Yujiahe River catchment is a typical and relatively isolated catchments on the northern slope of the Qinling Mountains. More than 240 kiwifruit orchards were surveyed face-to-face, combined with questionnaire records in two consecutive years (2012 and 2013). The investigated items included orchard basic situations, planting area, fruit varieties, tree ages, densities, fertilizer rates, fertilizer varieties, fertilizer nutrient content, fertilization methods, fruit yield and irrigation. The nutrient input from chemical fertilizers in kiwifruit orchards were calculated according to the actually surveyed chemical fertilizer application rates and the nutrient content labeled on these fertilizers. The nutrient input from organic fertilizer were calculated based on the standards provided by the Chinese Organic Fertilizer Nutrients Record. The reasonable fertilizer rates in kiwifruit orchards were determined on the basis of our study in combination with the regional literatures, and further the nutrients input status were evaluated.【Results】 The investigation results and literature summary suggested the recommended fertilizer rates were N 375-500 kg/hm2, P2O5186-186 kg/hm2, K2O 286-350 kg/hm2 and organic fertilizers 30000-65000 kg/hm2, respectively, the N∶P2O5∶K2O ratio was about 1∶0.5∶0.73 when the yields of kiwifruits are within 24-42 t/hm2. The actual nutrients input surveys showed: organic fertilizer are rarely applied, approximately 36.4% of orchards never have any manure input; In the kiwifruit orchards using organic fertilizer, the applied amount were seriously insufficiently in about 94.3% of the orchards, the nutrient provided by manures was less than 30% of the total nutrient inputs. Excessive application of N fertilizer is very common with an average input of N 891 kg/hm2. Only 5.0% of the investigated orchards apply reasonable amount (N 375-500 kg/hm2), 22.7% apply N of 500-750 kg/hm2, and 59.1% more than 750 kg/hm2. The ratio of orchards with a reasonable phosphate fertilizer input (P2O5 186-266 kg/hm2) was 19.4%, low input (P2O5186 kg/hm2) and excessive input (P2O5266 kg/hm2) were 28.9% and 51.7%, respectively. The orchards with reasonable potassium application rate (K2O 286-350 kg/hm2) was only 10.7%, with low input (K2O286 kg/hm2) and excessive input (K2O350 kg/hm2) were up to 30.6% and 58.7%, respectively.【Conclusions】 The organic fertilizer inputs in the kiwifruit orchards in the Yujiahe catchments was extremely inadequate, N fertilizers were generally excessively, and excessive and deficient application of phosphate and potassium fertilizers existed simultaneously. Therefore, it was strongly suggested to increase organic fertilizer inputs, reduce nitrogen fertilizer, strengthen the reasonable application of phosphate and potassium in kiwifruit production in future. The widely distribution of sloped cultivated lands in this region require optimizing nutrient management and controlling nutrient losses in the future research.