Ecological and Economic Benefits of Vegetation Management Measures in Citrus Orchards on Red Soils1

A three-year experiment was conducted to investigate and compare the economic and ecological benefits of six types of vegetation management measures in citrus orchards of the hilly red soil region of the eastern part of China. Six vegetation treatments, including tillage without herbicide (clean tillage) and no tillage without herbicide (sod culture) and with herbicide paraquat (paraquat), glyphosate (glyphosate), glyphosate-glyphosate-paraquat (G-G-P), and paraquatparaquat-glyphosate (P-P-G), were applied in the citrus orchards on a clayey red soil with slopes of 8° and 13° and a sandy soil with slope of 25°. The results showed that the sod culture, paraquat, glyphosate, G-G-P, and P-P-G treatments reduced surface runoff by 38.8%, 42.5%, 18.7%, 28.7%, and 37.5%, then the soil-water losses by 55.5%, 51.7%, 39.9%, 46.8%, and 50.0%, and the N, P, and K nutrient losses by 60.3%, 50.2%, 37.0%, 41.8%, and 45.4%, respectively, as compared with the clean tillage treatment. The weed regeneration ratios with the treatments of clean tillage without herbicide, paraquat, glyphosate, G-G-P, and P-P-G were reduced by 55.1%, 67.2%, 30.3%, 36.8%, and 51.2%, respectively, as compared with the sod culture. The sod culture, paraquat, glyphosate, G-G-P, and P-P-G treatments could increase the soil fertility (annual accumulation of N, P, K, and OM) by 7.1%, 6.9%, 5.3%, 6.2%, and 6.6%, respectively, whereas the clean tillage treatment without herbicide reduced soil fertility by 4.4% after the three-year experiment. The citrus fruit yields in the treatments of paraquat, glyphosate, G-G-P, and P-P-G increased by 7%–10%; the soluble solid, total sugar, total acidity, sugar-acid ratio, and single fruit weight of citrus fruits of all treatments except sod culture significantly (P> 0.05) exceeded that of the clean tillage treatment. In general, the paraquat treatment showed the best economic and ecological benefits among the six treatments; therefore, it could be regarded as the best available vegetation management measure in citrus orchards of hilly red soil region to retain water and soil, enhance soil fertility, and improve the yield and quality of citrus.