Changes in Soil Fertility Status under Long-term Intensive Sugarcane Production System at Wonji-Shoa Sugar Estate in Central Ethiopia

Abstract

Sugarcane yields at Wonji-Shoa Sugar Estate (WSSE) in central Ethiopia have declined by 48% over the last 70 years. Previous studies suggest that a decline in sugarcane yield is attributed to long-term intensive production system and the subsequent depletion of soil fertility. Hence, it was hypothesized that the soil fertility in the WSSE has been depleted, potentially contributing to the yield decline. To test this hypothesis, a series of bio-sequential soil samples were taken from adjacent cultivated lands (CL) and uncultivated lands (UL) in the two categories of WSSE: the old plantation (OP) and the new plantation (NP) lands, which have been cultivated for 70 and 13 years, respectively. The samples were analyzed for selected soil properties and compared using the t-test statistical tool. The results revealed that the soil organic carbon, total nitrogen, available phosphorus, exchangeable potassium, sulfur, zinc, and EC of the OP have declined significantly by 16%, 13%, 50%, 39%, 82%, 15%, and 58%, respectively, whereas no significant decline was observed in the NP. Calcium, magnesium, sodium, manganese, copper, and boron didn’t decline significantly in both plantations. The rating of organic carbon, available phosphorus, sulfur, boron, and EC were below the critical values. The findings confirm that the major soil properties of WSSE have dwindled as a result of the long-term intensive production system and appear to be responsible for the yield decline. Therefore, it is crucial for the sugar estate to design appropriate soil fertility management strategies to arrest the declining yields and produce the crop sustainably.