Evidence of Soil Health Benefits of Flooded Rice Compared to Fallow Practice

Flooded rice (Oryza sativa L.) in south Florida is grown commercially in rotation with sugarcane and vegetables. From 2008 to 2018, rice production has doubled. During the spring-summer, nearly 200 km2 of fallow sugarcane land is available for rice production. In 2017, approximately 113 km2 of rice were planted in the region. The net value of growing rice as a rotation crop far exceeds its monetary return. This study evaluated soil health parameters before and after rice cultivation and compared them against two other common summer farming practices - fallow fields and flooded-fallow. The soil health parameters that were tested as part of this study included soil pH, bulk density, water holding capacity, cation exchange capacity, organic matter, active carbon and nutrient content. Results indicated an increase in soil pH, and a significant reduction in soil bulk density due to rice cultivation. Water holding capacity increased significantly under all flooded land use practices compared to fallow fields. Cation exchange capacity significantly increased when sugarcane fields were cultivated with rice and ratoon rice, nearly doubled from 58 to 101 cmolc kg-1. Small, yet significant 3% increase in organic matter was observed when sugarcane fields were cultivated with ratoon rice. Almost 16 g kg-1 of active C is being generated within fallow soils, whereas less than half that under flooded practices, limiting the amount of soil loss via oxidation. Based on the soil health index, rice cultivation and flooded-fallow improved overall soil quality compared to fallow lands.