Resumo

TORRES DUGGAN, Martin; RODRIGUEZ, Mónica B; LAVADO, Raúl S  e  MELGAR, Ricardo. Agronomic efficiency of elemental sulphur in wheat relative to a soluble sulphur source in the Pampas Region. Cienc. suelo [online]. 2010, vol.28, n.1, pp.67-77. ISSN 1850-2067.

Agronomic efficiency of elemental sulphur (AE) compared with soluble and S-sulphate sulphur sources depends on reactivity of AE (e.g. particle size) and environmental conditions (soil and climate). Although there is published information suggesting that elemental sulphur has similar effectiveness than soluble sulphur sources, the information is not conclusive. We hypothesized that agronomic efficiency of AE and soluble S sources are similar under the Pampas Region conditions. The objectives of the study were to: i. Evaluate S grain response to a reactive source of AE compared to a soluble S source under different S rates and soil and climate conditions. ii. Compare, for the group of experiments, agronomic S efficiency between S sources. iii: Relate S responses with soil and climatic variables. Eight field experiments were conducted during two successive years on cropping systems in the Pampas Region. The experimental design was a randomized complete block with four or six replicates and a factorial treatment arrangement (factor 1: S source, factor 2: S rate). The treatments were: check (without S application), fertilization with a micronized source of AE (95% of S) and a fertilization treatment with ammonium sulphate (SA, 24%). Both sulphur sources were applied at two S rates. Sulphur rates were 10 and 30 kg ha¹ (year 1) and 15 and 30 kg ha^-1 (year 2). In the first year, wheat responded significantly to S in four of five sites (p<0.05) with yield increases of 231 to 857 kg ha^-1. Significant yield increases were observed in all sites in the second year, ranging from 702 to 2,119 kg ha^-1. There were no significant differences in grain yield among S sources, rates or interaction source x S rates (p>0.05) in most sites. When all sites were combined, sulphur sources presented similar agronomic S efficiencies (p>0.05). The lower S rate (10 or 15 kg ha¹) was enough to provide S to the crop under the Pampas Region conditions. Grain yield responses to S were positively correlated with organic matter content and rainfall (during tillering or the whole crop cycle) and inversely associated with SO₄^2- at planting, although with a poor adjustment. No correlation was detected between S response and temperatures during tillering or the whole crop cycle.

Palavras-chave : Elemental sulphur; Ammonium sulphate; Agronomic efficiency; Response.

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