Effects of Long-Term Fertilization on Walnut Yield and Soil Nutrients at Different Growth Stages
[Objective]This study aimed to explore the effects of different fertilization treatments on soil nutri-ents and yield during the walnut growth period,to clarify the optimal fertilization scheme for improving soil fertility in walnut orchards,and to provide a scientific basis for the fertilization of walnut trees.[Method]In this study,five fertilization treatments were applied to the soil of the ′Xiangling′ walnut orchard:no fertiliza-tion(CK),single fertilizer(CF),chemical fertilizer plus organic fertilizer(CF+OF),chemical fertilizer plus bio-organic fertilizer(CF+BOF),and chemical fertilizer plus organic fertilizer plus bio-organic fertilizer(CF+OF+BOF).The effects of combined organic and inorganic fertilizers on walnut yield and soil nutrients were analyzed by measuring soil organic matter(SOM),total nitrogen(TN),nitrate nitrogen(NO3--N),ammonium nitrogen(NH4+-N),available phosphorus(AP),and available potassium(AK)during the key growth stages of walnuts.[Result]Walnut yields treated with CF,CF+OF,CF+BOF and CF+OF+BOF were 1.79,2.36,3.25 and 4.11 times that of the CK treatment,respectively.The SOM con-tent peaked during the flowering stage,with the following order:CF+OF+BOF>CF+BOF>CF+OF>CF>CK,reaching a maximum of 15.88 g/kg in the CF+OF+BOF treatment.CF+OF,CF+BOF and CF+ OF+BOF treatments were significantly higher than CK and CF(P<0.05).The TN content was high-est during the hard core stage,with the CF+OF+BOF treatment being significantly higher than the others at 4.70 g/kg(P<0.01).The NO3--N content in the CF+OF+BOF treatment during the bud-ding stage was significantly higher than other treatments at 12.54 mg/kg(P<0.05).The NH4+-N con-tent in the CF treatment was significantly higher than others at 28.56 mg/kg(P<0.01).The AP con-tents for CF+OF,CF+BOF and CF+OF+BOF peaked during the embryonic stage at 79.51,88.33 and 117.61 mg/kg,respectively,and were significantly higher than CK and CF(P<0.05).The AK content for CK,CF,CF+OF and CF+OF+BOF peaked during the flowering stage at 140.86,148.40,160.67 and 164.57 mg/kg,respectively.[Conclusion]Compared with CK,CF,CF+OF,CF+ BOF,CF+OF+BOF all increase the nutrient content of soil,and the combined application effect of organic and inorganic fertilizer is better than CF,among which CF+OF+BOF has the best effect on soil fertility im-provement,therefore,the combined application of organic and inorganic fertilizer provides stable and continu-ous supply of nutrients to walnuts throughout the growth and development process,promotes the absorption and utilization of soil nutrients by walnut trees,and significantly increases the yield of walnut fruits.
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