Liquid fertilizer application to ratoon cane using a soil punching method

Sugarcane is a semi-perennial crop that is cultivated for five or six harvest cycles before replanting. Following annual mechanized harvest, nitrogen (N) fertilizer is commonly applied during the ratoon cane sprouting phase through furrows along the side of plant rows (subsurface application) or banded on the surface. With subsurface application, mechanical operations are hampered by the trash coverage that remains after harvest; furthermore, opening furrows can partially damage roots. However, with soil surface application, nutrient uptake efficiency is decreased as a result of microbial immobilization and losses through ammonia volatilization and runoff. Thus, to achieve subsurface application for ratoon cane with minimal mobilization of the system (soil, straw and roots), this work aimed to (i) develop and evaluate a mechanical prototype that enables a soil punching process in ratoon cane and (ii) evaluate the cane yield using the soil punching method for liquid N fertilizer injection compared to liquid N fertilizer applied alongside of plant rows on the surface and subsurface (through furrows). To evaluate the punching mechanism, we performed a kinematic simulation (puncher tip displacement and injection time interval), tests in a soil bin and ratoon cane field. Based on prototype operations, the average distance between applications was 300 mm, with an average depth up to 90 mm, which was similar to the design requirements. Regarding results of liquid N fertilization methods in a ratoon cane field, we found that the incorporation treatments (soil punching and subsurface application through furrows) achieved slightly better cane yield (98-96 Mg ha−1) when compared to the surface application (91 Mg ha−1) and control treatment (75 Mg ha−1). In general, the soil punching was considered as a promising alternative method for supplying liquid fertilizer at the subsurface using low-energy power (approximately 745 W) with minimal environmental impact.