Effect of Fresh and Composted Organic Amendment on Soil Compaction and Soil Biochemical Properties of Citrus Orchards in the Mekong Delta, Vietnam

摘要

The objectives of this study were to evaluate the degree of soil degradation and the effect of organic amendment on improving soil properties and fruit yield of citrus orchards on alluvial soil. Sixty raised beds of citrus orchards were selected in arange of age from less than 10 years, 12-18 years, 22-28 years and 30 years. Soil samples were collected and analyzed for selected soil properties. The effects of 10t ha~(-1) sugarcane filter cake compost plus Trichoderma spp. and 201 ha~(-1) of fresh Tithonia diversifolia were studied in orange orchards where the raised beds had been constructed for more than 26 years. Both these organic treatments were combined with recommended inorganic fertilizer (250gN-200g P_2O_5 -120g K_2O.plant~(-1) ), and compared with usual farmer practice (628g N-327g P_2O_5- 64g K_2O.plaht~(-1) ). Soil analyses indicated that soil degradation occurred in 30 year old raised beds constructed. Soil aggregate stability was low and soil strength resistance was in the range of soil compaction. Soil organic matter, cation exchange capacity (CEC), and base saturation percentage were low compared to other raised beds (P<0.05). Amendment with sugarcane filter cake compost (plus Trichoderma spp.) and fresh Tithonia diversifolia ledto an increase soil organic matter content, available nitrogen and phosphorus, CEC, percentage base saturation, soil respiration, soil aggregate stability and to reduced soil compaction (P<0.05). Fruit yield was also improved with both treatments compared with the farmers usual practice, which gave low fruit yield (P<0.05) and resulted in poor soil quality in terms of soil physical and chemical properties. While both treatments enhanced fruit yield, the application of 10t.ha~(-1) of sugarcane filter cake was more effective than the application of 20t ha~(-1) of fresh Tithonia diversifolia.