Agricultura de precisão em áreas irrigadas com pivô central no Rio Grande do Sul

Abstract

The search for new technologies that could increase crop yields encourages a growing number of Brazilian farms to use precision farming. Although precision farming principles are not new, only in last two decades has it been applied in a whole cycle in Brazil. The center pivot is increasing the area of implementation, although economic analysis is scarce. The knowledge of soil and yield variability is an important tool to achieve positive results in irrigated areas. The main objective of this work was to quantify the soil fertility indicators within the whole areas, and soil physics and soil fertility indicators within management zones, which were defined based on temporal yield maps. The net return of the irrigated area was compared to dry cropland in one farm. The work was carried out in two grain farms in Trindade do Sul in 51.8 ha and Palmeira das Missões in 57.3 ha. The soil is an Oxisol and the weather is cfa following Koeppen classification. The sampling in each management zone was in 0-0.05, 0.05-0.10 and 0.10-0.20 soil depth. The yield monitoring was done by Massey Fergurson MF 34 and CASE 2388 combines. The yields were monitored in 2005/06 and 2006/06 to black bean (Phaseolus vulgaris) in Trindade do Sul. In Palmeira das Missões the maize (Zea mays) were monitored in 2002/03 and 2003/04 (irrigated) and 2001/02 and 2004/05 (dry land). In both farms no-tillage system has been used for ten years. The soil data was analyzed by statistic, spatial variability and multivaried analysis. The yields were classified in low, medium, and high yield. The farms showed different soil indicators. In Trindade do Sul 55.8% of the area had pH water < 5.4, while in Palmeira das Missões 100% of the area had pH water > 5.7. The K, in both farms, had levels higher than 118 mg dm-3. 7.1% of area in Trindade do Sul showed the P lower than 6 mg dm-3 and in Palmeira das Missões the P levels were higher than 11 mg dm-3. The P had the lower range among the nutrients investigated. The multiple analyses showed that 6 and 4 main components explained 83 and 87% of yield variation in Trindade do Sul and Palmeira das Missões, respectively. In Palmeira das Missões the soil physics indicators in each yield zones showed that lower yields were associated with bulk density of 1.42 g cm-3, macroporosity of 8% in 0.1 to 0.2 m depth, AWC of 32.4 mm. The economic analysis indicated that the irrigated area allowed 19.7% of increase in net return compared to dry land.