关键词: 果园生草, 绿肥, 中微量元素, 腐解, 桃园, 土壤养分

Abstract:

【Objective】The objective of this study is to simulate green manure management in the actual production of grassy peach orchards, investigate the release law of medium and trace elements (MTE) after green manure was continuously incorporated into the soil, and to examine the effects of continuous grass on soil available nutrients in peach orchards, so as to provide reasonable grass planting and scientific formulation of nutrient management measures in peach orchard.【Method】The grass-planting experiment was carried out in a peach orchard where grass was sown in 2016. Two treatments were set up: inter-row planting of ryegrass (RG) and hairy vetch (HV), and the mulching of black ground fabric (BF) was used as the control. In 2021 and 2022, soil available MTE content was measured at four key stages: pre-surface return (before mowing) and pre-burial (before incorporation) of green manure. The nutrient release characteristics of green manure were conducted using the nylon net bag method. The first stubble green manure was subjected to 100 d of surface decomposition followed by 350 d of burying decomposition, and the second stubble green manure was subjected to 100 d of surface decomposition. Element release patterns and residual quantities per unit area of green manure residues were analyzed over two consecutive years.【Result】There was no significant difference in the initial content of Fe between the two types of green manure, while the initial content of Ca, Mg, and Cu in hairy vetch was significantly higher than in ryegrass. The accumulated release ratios of Ca, Mg, Mn, Cu, and Zn in ryegrass ranged from 2.65% to 55.43% during the surface decomposition of the first crop of green manure, all of which were significantly higher than those in hairy vetch. After the burying back to the field, the accumulated release ratios of Mn, Cu, and Zn in the residue increased overall. By the end of the test, the accumulated release ratios of Mn and Zn in hairy vetch reached 82.59% and 90.02%, respectively, which were significantly higher than those in ryegrass. Both species exhibited persistent Fe accumulation, with accumulated release ratios reaching -360.78% (RG) and -371.63% (HV) after 450 d. During the surface decomposition of the second crop green manure, Ca, Mg, and Zn were enriched in hairy vetch only, while Fe, Mn, and Cu were enriched in both of green manures. The differences in the release levels of various elements resulted in the residual amounts of Ca and Mg per unit area of green manure, which reached their highest values after 350 d of returning the first crop of green manure. However, the residual amounts of Fe, Mn, and Cu continued to increase at the end of the test. After continuous grass returning, the increase range of soil exchangeable Ca content in hairy vetch and ryegrass plots exceeded 13.13% and 23.56%, respectively, and the exchangeable Mg content increased by more than 13.85% and 20.51%, respectively. Compared with BF, by the end of the experiment, the available Mn content in the soil of HV increased by 63.16%, and the available Zn content in RG increased by 134.16%. However, the available Cu content of the HV and RG decreased by 37.90% and 36.06%, respectively, and the available Fe content was only 46.87% and 34.61% of the BF, respectively.【Conclusion】In the long run, perennial green manure application enhances soil exchangeable Ca and Mg, but reduces available Fe and Cu in peach orchards. In the short term, MTE fixed by green manure fails to completely release after 450 d of returning, and the enrichment time of Fe is the longest. In the early stage of grass planting in peach orchards, it is advisable to choose the mixed coverage mode of covering ground fabric in rows or under tree trays and planting green manure between rows. During the growth period of green manure, supplemental MTEs fertilization should be applied to effectively mitigate nutrient competition between peach trees and green manure and to promote the improvement of soil fertility in peach orchards.

Key words: orchard grass, green manure, medium and trace elements, decomposition, peach orchard, soil nutrient