Soil tillage methods in unburnt, mechanically harvested systems.

THIS STUDY was conducted on two soil types, Red and Yellow-red latosols, under mechanically harvested, unburnt sugarcane. A randomised block design with split plots was applied, with six repetitions. The main treatments on each soil type were: (MT) minimum tillage – old ratoon killed with glyphosate; (RT) reduced tillage – old ratoon killed with glyphosate + subsoiling; (PT) reduced tillage – old ratoon killed with glyphosate + mouldboard plough and (CT) conventional tillage – harrowing + subsoiling. The sub-plots were planted with three varieties (RB855113, RB855257 and RB855536). The observations were performed in the final ratoon and plant cane crops. Physical and chemical properties of soils, and cane and sugar yields were recorded, and an economic analysis was conducted. No interaction was found between soil tillage systems and varieties, although the variety RB855536 gave the highest yield. Among the soil tillage systems, the reduced tillage with glyphosate and mouldboard plough produced the greatest yield and economic return. Among the analysed physical parameters, differences were not detected among the preparation systems, although the minimum prepare (MP) showed the biggest values of resistance to the penetration of the soil. For both soils, the reduced tillage method (PT) performed better than the other systems. Introduction The adoption of a certain system of soil preparation can constitute the first step towards high production because it can affect the whole sugarcane cycle, which lasts up to five years. Soil preparation has an important effect on productivity, as it directly affects the physical, chemical and biological characteristics of the soil, which can benefit or inhibit the development and the production of the crop. The objective of the present study was to evaluate two soils with four different systems of soil preparation, under three sugarcane varieties, for their effects on cane and sugar production and physical and chemical soil properties. Economic analyses of the systems were conducted. Material and methods Two field trials were established in the region of Ribeirao Preto, in the Corona sugar-mill production area, Usina Bonfim, in the municipal district of Guariba, in Sao Paulo, Brazil. The soils used in the study were Red and Yellow-red latosols, which have been under sugarcane cultivation for several years and were mechanically harvested, without burning, for the last four years. Each field trial was set up in a randomised block design with split plots to evaluate the effects of different methods of soil preparation and varietal behaviour. The main treatments constituted four methods of soil preparation, viz. (MT) minimum tillage – old ratoon killed with