Evaluation of moisture in sugarcane straw bales piles in the field using geoestatistical techniques

Abstract

Sugarcane is planted in 23 Brazilian states totaling more than 10.2 million hectares, and for each hectare there are around 10 tons of straw (db), biomass resulting from mechanized harvesting. In Brazil, the straw is of relevance to the sector by the volume produced and can be used for the production of steam, electricity, second-generation ethanol, and paper, and the bale is the most used form in field harvesting. Due to the sugarcane harvesting, it is necessary to store the bales produced in large piles for up to one year. The best way to store bales of straw is still unknown, which leads to biomass losses, higher costs, and reduced profits. In order to provide more efficient techniques for the storage of straw, we evaluated the distribution of moisture inside the piles stored in the field, without coverage, in two baling densities, three accumulated amounts of precipitation, and the picking or not of the straw before the baling. Over all, nine piles were assembled, and 294 moisture points per pile were sampled. The analysis and data processing consisted in verifying the existence of spatial dependence, and existing, the data interpolation was carried out by the ordinary kriging method by prediction, to estimate values at unmeasured locations and to create the moisture distribution maps in the stacks. In all the evaluated treatments the existence of spatial dependence was observed, being possible the use of geostatistical methods for analysis. The spherical model was the most appropriate to describe the behavior of moisture inside the cells. The chopping of straw affected the distribution of moisture, as well as the density and amount of precipitation accumulated. For short periods of storage, bales of chopped straw remained drier, while for longer periods, bales of chopped straw remained drier. High-density bales were more efficient in maintaining the driest biomass.