Sweet Sorghum Performance Affected by Soil Compaction and Sowing Time as a Second Crop in the Brazilian Cerrado

Abstract

Increasing attention has recently been given to sweet sorghum as a renewable raw material for ethanol production, mainly because its cultivation can be fully mechanized. However, the intensive use of agricultural machinery causes soil structural degradation, especially when performed under inadequate conditions of soil moisture. The aims of this study were to evaluate the physical quality of aLatossolo Vermelho Distroférrico (Oxisol) under compaction and its components on sweet sorghum yield forsecond cropsowing in the Brazilian Cerrado (Brazilian tropical savanna). The experiment was conducted in a randomized block design, in a split plot arrangement, with four replications. Five levels of soil compaction were tested from the passing of a tractor at the following traffic intensities: 0 (absence of additional compaction), 1, 2, 7, and 15 passes over the same spot. The subplots consisted of three different sowing times of sweet sorghum during the off-season of 2013 (20/01, 17/02, and 16/03). Soil physical quality was measured through the least limiting water range (LLWR) and soil water limitation; crop yield and technological parameters were also measured. Monitoring of soil water contents indicated a reduction in the frequency of water content in the soil within the limits of the LLWR (Fwithin) as agricultural traffic increased (T0 = T1 = T2>T7>T15), and crop yield is directly associated with soil water content. The crop sown in January had higher industrial quality; however, there was stalk yield reduction when bulk density was greater than 1.26 Mg m-3, with a maximum yield of 50 Mg ha-1 in this sowing time. Cultivation of sweet sorghum as a second crop is a promising alternative, but care should be taken in cultivation under conditions of pronounced climatic risks, due to low stalk yield.

Época De Semeadura Sobre Cultivares De Sorgo Sacarino / Planting Season on Sorghum Cultivars of Saccharine

“…Todavia, a maior valor de ºBrix deve estar associado à produtividade de colmos e caldo que resultará em maior produtividade de etanol. Guimarães Júnnyor et al (2015) verificaram redução na produção de colmo e no valor de ºBrix em semeadura tardia, ocasionado pelas condições climáticas, devido a deficiência hídrica.…”

Soil Physical Quality in Sugarcane Field Under Cover Crop and Different Soil Tillage Systems

“…Intermediary values needed to estimate LLWR were(i) soil moisture at field capacity (θ FC ), (ii) soil moisture at permanent wilting point (θ PWP ), (iii) soil moisture at 0.10 m 3 m -3 air-filled porosity (θ AP ) was, and (iv) soil moisture at 2.5 MPa soil penetration resistance (θ PR ) as proposed by Severiano et al (2011), Gonçalves et al (2014), Guimarães Júnnyor et al (2015).…”

“…Values of Bd c higher than these probably present limiting conditions to plant development despite the water content in the soil due to structural restrictions. Guimarães Júnnyor et al (2015) evaluated physical quality of a oxisol (clay 44%) and found Bd c of 1.36 Mg m -3 . According to Petean et al (2010), low Bd c increases the possibility of Bd achieving critical values (Bd > Bd c ), suggesting a higher incidence of limiting physical conditions for plant development.…”

“…In an attempt to integrate and simplify monitoring of soil physical quality, various authors have used the least limiting water range (LLWR) as an indicator of soil structural quality (Araújo et al, 2013;Gonçalves et al, 2014;Guimarães Júnnyor et al, 2015) and to evaluate the impact of several soil management practices (Tormena et al, 1998;Tormena et al, 2007). The LLWR is defined as the range of soil water content in which limitations to plant root growth correlated with water potential, aeration and mechanical resistance are minimal (Silva & Kay, 1997).…”