Espaçamentos entrelinhas em cultivo de cana-de-açúcar: parâmetros físicos do solo e componentes de rendimento

Abstract

Soil compaction has caused a decline in the productivity of Brazilian sugarcane plantations, a consequence of machine traffic in the mechanized harvest. The use of combined spacings is cited to control this problem. But few studies have been carried out regarding the spatial behavior of soil physical attributes and their relation to the plant attributes. The objectives of this study were: i) Evaluate and relate soil parameters and sugarcane production components in three configurations of spacing between rows in two crop cycles; and ii) To verify the spatial distribution of soil compaction in two configurations of spacing between rows in the third cycle after planting. To meet the first objective, three types of spacing between lines of the culture were evaluated: the row spacing single – 1.5 m (LS), double combined – 0.4 x 1.7 m (LD) and triple combined – 0.3 x 0.3 x 1.5 m (LT). Soil samples were collected in the 0.00-0.10 m layer in 2013 and 2014, during the second and third cycle after planting, respectively, along a 50 m transect in the culture rows. Were determined Bulk density (Ds), total soil porosity (Pt), macro (Ma) and microporosity of the soil (Mi), soil penetration resistance (RP), soil water contents at field capacity (θCC) and permanent wilting point (θPMP) and available water capacity (CAD). At each point of the transect was also evaluated attributes of plant: stalk height (H), stalk diameter (DC), total soluble solids (Brix), the number of stalk per square meter (NCM2) and stalk mass (MC). An exploratory analysis, a spatial autocorrelation, a cross-correlation and an application of state space models were performed. As for the second objective of this study, in 2016, during the third cycle after planting, in two types of spacing between rows (single – 1,5 m and double combined – 0,4 x 1,5 m), samples with a preserved structure were collected in the soil layer of 0.00 - 0.10m in a sample grid of 0.5m x 1m, totaling 100 sampling points for each type of spacing. Were determined Bulk density (Ds), total soil porosity (Pt), macro (Ma) and microporosity of the soil (Mi) and soil penetration resistance (RP). An exploratory analysis, semivariance analysis, semivariograms preparation, adjustment of semivariograms models, kriging and mapping of each variable for the two spacing were performed. The soil physical attributes satisfactorily explained the spatial variability of the components of sugarcane production in row spacing single and triple combined in the third cycle after planting through the state-space approach. In the second cycle after planting, the variability of the components of sugarcane production was not explained by the physical attributes of the soil. The double row spacing showed the lowest degradation of soil physical quality after two crop cycles, indicating a soil compaction control. The productivity in the single row spacing and double row spacing were similar with lower productivity in the triple row spacing in the two crop cycles.