The Practice of Green Cane Trash Blanketing in the Irrigated Zone of Mauritius: Effects on Soil Moisture and Water Use Efficiency of Sugarcane

Abstract

Sugarcane growers in Mauritius are using mechanized harvesting to reduce costs. This practice results in a trash blanket which contributes to conserve soil moisture, but potential savings in irrigation water have yet to be quantified. An on-farm study was undertaken at three sites in the irrigated coastal zone of Mauritius under sub-humid to humid mega-thermal climate and soils that were oxisol or inceptisol. Trials were conducted in ratoon crops under centre pivot irrigation and treatments with or without trash blanket, as well as different irrigation regimes. Sensors were used to log soil moisture data at 20, 40 and 60 cm depths. Increased drainage was observed under trash blanket during rainfall events and cumulative drainage for a 4-month wet period amounted to 43 and 240 mm for no-trash and trash blanket treatments respectively. Daily crop water use was higher with trash blanket, consumption being 4.9 and 5.1 mm day⁻¹ compared to 4.2 and 4.6 mm day⁻¹ for no-trash during peak growth at Savannah and Médine. Sugarcane yield was higher by 7.2 and 6.6 t ha⁻¹ year⁻¹ with trash blanket compared to no-trash, whereas water use efficiency increased by 8 and 9 kg ha⁻¹ mm⁻¹. At Saint Antoine, trash blanket increased the yield difference between irrigated and rainfed crops by 8.6 t ha⁻¹ and improved water use efficiency by 7 kg ha⁻¹ mm⁻¹ when irrigated. Seasonal water equivalence of the trash blanket amounted to 62, 54 and 72 mm water at Savannah, Médine and Saint Antoine, a potential saving of 10–15 % in irrigation water.