Variable-rate lime application in Louisiana sugarcane production systems

Abstract

Precision agriculture may offer sugarcane growers a management system that decreases costs and maximizes profits, while minimizing any potential negative environmental impact. The utility of variable-rate (VR) lime application in the initial production year (plant cane) of a 3-year sugarcane crop cycle was investigated at three locations planted to the cultivar LCP 85–384 for a total of nine site-years. A conventional, uniform-rate (UR) lime application method was compared to a VR application method and a no-lime control. Prior to lime application, soil samples (0–200 mm) were taken on a 0.4 ha grid to produce VR application maps. Soil samples were also taken after each crop of the 3-year production cycle to determine effects of lime application on soil properties. The combined results showed that neither the UR nor VR lime application method consistently improved cane or sugar yields over the no-lime control. Cane and sugar yields at Naquin Farms (NF) were increased with both the UR and VR methods, with the UR method having a slight advantage. At St. Louis Plantation (SLP), only the VR method in the first-ratoon crop increased cane and sugar yields and there were no yield differences due to lime application at Ellendale Plantation (EP). At NF and SLP, application of lime in the plant-cane crop increased soil pH and available phosphorus over the 3-year production cycle. At EP, lime application did not influence any of the soil properties measured. The failure to get a yield response from lime application at SLP and EP may have been due to the fact that fertility levels at planting were already greater than those at NF and the nitrogen fertilizer rates used by the grower at EP were higher than those at either SLP or NF. This may have obscured any positive yield effects that would be realized from increased nutrient availability. It is also possible that multiple VR lime applications will be required over a number of crop cycles to stabilize soil pH levels before a consistent positive effect on cane and sugar yields is observed with VR application. This possibility will be investigated in future studies.