Abstract:[Objective] Green manure is a clean biological organic fertilizer source. Reasonable planting and utilization between rows in kiwifruit orchards is an important technical measure to solve the shortage of organic fertilizer sources, protect the soil environment, improve soil quality, and promote sustainable agricultural development. The soil fertilization effect of green manure returning to the field is influenced by the type of green manure, soil habitat, and orchard climate. Therefore, the decomposition characteristics and nutrient release laws of different varieties of green manure returning to the field after green manure returning in kiwifruit orchards are studied, in order to provide theoretical basis for the planting and utilization of green manure in kiwifruit orchards in southern Shaanxi and the fertilization of soil fertility in the later stage of growth. [Method] The field net bag burial method was used to study the decomposition characteristics and nutrient release patterns of four types of green manure, Lolium perenne L., V. sativa L., Vicia villosa Roth., and Astragalus sinicus L., in the 10 cm soil layer between kiwifruit rows after 142 days of compaction. [Result] The decomposition was divided into three stages: rapid decomposition period (0-24 days), moderate decomposition period (25-41 days), and slow decomposition period (42-142 days). After 142 days of decomposition, the cumulative decomposition rates of Lolium perenne L., V. sativa L., Vicia villosa Roth., and Astragalus sinicus L. were 93.63%, 93.37%, 91.48%, and 74.45%, respectively; The average cumulative release rates of C, N, P2O5, and K2O nutrients were 88.23%, 82.95%, 98.58%, and 77.15%, respectively. The average N release amounts were 2373.58, 144.76, 156.30, and 16.10 kg·hm-2, respectively. The decomposition rates of C, N, and K2O fluctuated significantly 24 days before decomposition, while the decomposition rates of phosphorus fluctuated significantly 41 days before decomposition; After 142 days of decomposition, the C, N, K2O, and P2O5 nutrient release rates of Lolium perenne L. were 3015.28, 132.38, 274.53, and 23.72 kg·hm-2, respectively, with nutrient cumulative release rates of 93.63%, 89.16%, 99.28%, and 92.65%. The nutrient cumulative release rates of V. sativa L. were 2278.46, 193.69, 109.56, and 18.46 kg·hm-2, respectively, with nutrient cumulative release rates of 91.48%, 89.85%, 98.53%, and 82.47%; The Vicia villosa Roth were 2855.68, 173.49, 156.61, and 17.09 kg·hm-2, respectively. The cumulative nutrient release rates were 93.37%, 83.67%, 98.72%, and 73.88%, respectively; The Astragalus sinicus L. were 1344.89, 78.47 , 84.50, and 5.12 kg·hm-2, respectively. The cumulative nutrient release rates were 74.45%, 69.11%, 97.81%, and 59.60%, respectively. The nutrient release rates of the four types of green manure were K2O>C>N>P2O5, with average cumulative release rates of 98.58%, 88.23%, 82.95%, and 77.15%, respectively. The decrease in dry matter mass among green manure varieties were as follows: Lolium perenne L.> V. sativa L.>Vicia villosa Roth.>Astragalus sinicus L.. The decomposition rate were as follows:Lolium perenne L.>Vicia villosa Roth.>V. sativa L.>Astragalus sinicus L. The release levels of C and K2O nutrients from various varieties of green manure were as follows: Lolium perenne L.> V. sativa L.>Vicia villosa Roth.>Astragalus sinicus L.. The release levels of N nutrients were as follows: Vicia villosa Roth.>Lolium perenne L.>V. sativa L.>Astragalus sinicus L.. The release levels of P2O5 nutrients were as follows: Lolium perenne L.>Vicia villosa Roth.>V. sativa L.>Astragalus sinicus L.. The release of C, K2O, and P2O5 from Lolium perenne L. were the highest, while the release of N from Vicia villosa Roth. were the highest. The cumulative decomposition rate and nutrient release rate of Astragalus sinicus L. were lower than the other three varieties. The C/N ratios of the four types of green manure are as follows: Astragalus sinicus L>Lolium perenne L.>V. sativa L.>Vicia villosa Roth., with ratios of 12.99, 12.74, 11.30, and 9.70, respectively. The C/N ratio of green manure was significantly positively correlated with dry matter mass, decomposition rate, release rate of C, N, P2O5, and K2O, as well as the accumulation of C, P2O5, and K2O. It was significantly negatively correlated with the accumulation and release rate of C and P2O5.【Conclusion】The application of three types of green manure, namely ryegrass, sweet potato, and arrow pea, can provide carbon, nitrogen, potassium, and phosphorus nutrients for kiwifruit orchards at 2716.47, 166.52, 180.23, and 19.76 kg·hm-2, respectively. The application of green manure is during the period of orchard germination, leaf development, flowering, and fruit setting. Adequate nutrient supply during this period is the key to ensuring fruit growth, development, and quality formation. The nutrients provided by the application of green manure play an important role in kiwifruit root growth and nutrient absorption. Returning green manure to the field enhances the effectiveness and persistence of soil nutrients, ensuring a sustained supply of nutrients for kiwifruit growth in the middle and later stages. Therefore, in kiwifruit orchards in southern Shaanxi, selecting Lolium perenne L., Vicia villosa Roth., and V. sativa L. as green manure and applying them to the soil can release nutrients into the soil, providing necessary nutrients for the growth and development of fruit trees.
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