Are the yield of sunflower and Paiaguas palisadegrass biomass influenced by soil physical quality?

Abstract

Soil compaction affects physical soil properties, which in turn influence crop growth, development and yield. The present study tested the hypothesis that the yield of sunflower achenes and Paiaguas palisadegrass biomass are influenced by soil physical properties. The effects of compaction were measured by the least limiting water range (LLWR), and its relationship with crop yield were studied. The experiment was conducted in the Rio Verde municipality, south-western Goias State, Brazil, on a Latossolo Vermelho Acriférrico típico (Typic Haplustox) soil and in accordance with a randomized complete block design, in which the treatments consisted of compaction levels established by zero, two, 10, and 30 passes of an agricultural tractor (with four replicates each). In the subplots, sunflower and Paiaguas palisadegrass were grown as monocropping and intercropping systems. The following indicators of soil physical quality were determined: bulk density (Bd), the LLWR, the Bd/alert bulk density of the LLWR (Bdalert) ratio, and the Bd/critical bulk density of the LLWR (Bdc) ratio. The correlations of these indicators with crop yield were calculated to define critical resistance values specific to each crop. The LLWR adequately described the physical quality of the soil resulting from compaction and was significantly correlated with crop yield. The relationship between sunflower and Paiaguas palisadegrass yield was modelled by a second-order equation featuring Bd and the Bd/Bdalert ratio (R2 = 0.77, ** and 0.74 **, respectively), with the greatest yield recorded when the Bd/Bdalert ratio was 1.0. Sunflower cultivation was extremely sensitive to soil compaction: when sunflower was grown as a monoculture or intercropped with palisadegrass, its yield decreased by 50 % or 80 %, respectively. However, the Paiaguas palisadegrass yield was influenced little by soil compaction. The limiting penetration resistance values for sunflower and Paiaguas palisadegrass were 1.5 MPa and 4.2 MPa, respectively.