Current status and evaluation of nutrient inputs in wolfberry orchards of different ages in Gansu, China

The wolfberry industry has become a characteristic pillar industry that promotes the rural economic development in many areas in Gansu Province. There are many problems in wolfberry orchards, such as unbalanced nutrient input, extensive management, low utilization rate, and high loss rate, which limit the high-quality, sustainable, and healthy development of the wolfberry industry. We investigated fertilization status and nutrient management problems of wolfberry orchards with different tree ages in Wuhe Town, Jingyuan County, Gansu Province. We put forward regulatory measures and suggestions for the optimized nutrient management of wolfberry orchards. The results showed that nutrient input of wolfberry orchards was generally dominated by chemical fertilizers (with an average of 72.6%). Nutrient input of organic fertilizers was insufficient (with an average of 21.3%). The problem was most prominent in old-aged wolfberry orchards, where the proportion of chemical fertilizer in the total nutrient input was as high as 81.1%, and the proportion of orchards with insufficient organic fertilizer nutrient input accounted for 94.1%. The optimized fertilization amounts for wolfberry orchards were N 244-361 kg·hm^-2, P₂O₅ 209-271 kg·hm^-2, K₂O 121-157 kg·hm^-2, and organic fertilizer 6-10 t·hm^-2 for young-aged orchards (≤4 years); N 354-446 kg·hm^-2, P₂O₅ 262-330 kg·hm^-2, K₂O 175-221 kg·hm^-2, and organic fertilizer 10-22.5 t·hm^-2 for middle-aged orchards (5-7 years); and N 222-265 kg·hm^-2, P₂O₅ 385-460 kg·hm^-2, K₂O 488-583 kg·hm^-2, and organic fertilizer 22.5-24 t·hm^-2 for old-aged orchards (≥8 years). Common problems in the chemical fertilizer input of wolfberry orchards include high phosphorus fertilizer input, and both insufficient and excessive application of nitrogen and potassium fertilizers. In young-aged orchards, the proportion of high nitrogen input accounted for 66.7%, the proportion of high phosphorus input accounted for 61.7%, and the proportion of high potassium input was 75.1%. In middle-aged orchards, the proportion of both high and low nitrogen input was about 40.0%, the proportion of high phosphorus input accounted for 68.4%, and the proportion of both low and high potassium input was about 41.5%. In old-aged orchards, the proportion of low nitrogen input accounted for 53.0%, the proportion of excessive phosphorus input accounted for 44.1%, and the proportion of excessive potassium input was 50.0%. In the study area, the input of organic fertilizers should be substantially increased, the amount of phosphorus fertilizers should be reduced, and the application ratios of nitrogen, phosphorus, and potassium in chemical fertilizers should be optimized. Such strategies would improve nutrient utilization rate, reduce nutrient losses and potential environmental pollution risks, and promote the sustainable and healthy development of wolfberry industry.