Gypsum application increases the carbon stock in soil under sugar cane in the Cerrado region of Brazil

Abstract

Gypsum is widely used in agriculture in the Cerrado region of Brazil to increase root volume and distribution in the profile of predominantly acidic soils with high aluminium toxicity. The gypsum-induced increase in the root system may be an effective strategy to increase sequestration of atmospheric CO2. However, few studies have investigated the relationship between the use of gypsum and carbon accumulation in the soil under sugar cane. In the present study, total carbon stock (TC) in the soil and its fractions were estimated after four growing seasons of sugar cane under gypsum application. The experiment was arranged in a randomised block design with four replicates and two treatments: control (0Mgha–1) and the technically recommended rate of gypsum application (5Mgha–1). Sugarcane stalk biomass and straw production were evaluated in plant cane and three ratoon crops. Soil samples were taken after evaluation of the third ratoon from seven layers (0–5, 5–10, 10–20, 20–40, 40–60, 60–80 and 80–100cm) to determine organic carbon, TC, particulate carbon (PC) and bulk density. Gypsum increased TC by 5.4 and 4.4Mgha–1 in the 0–100 and 40–100cm layers respectively. The PC pool in the 40–100cm layer was increased by 18.4%, whereas the carbon stock associated with mineral increased by 6.8% with gypsum application. Of the total increase in C stocks resulting from gypsum application, 80% occurred in the 40–100cm layer.