Straw Decomposition in Irrigated Soil: Comparison of Twenty‐three Cereal Straws

Abstract

The objective of this research was to evaluate field decomposition of 23 cereal grain straws. Straw samples of ‘Fieldwin’ and ‘Owens’ soft white spring wheats (Triticum aestivum L.); ‘Borah’ and ‘McKay’ hard red spring wheat; ‘Nugaines’, ‘Daws’, ‘Lewjain’, ‘Stephens’, and ‘Hill 81’ soft white winter wheats; ‘Weston’, ‘Manning’, ‘Neeley’ hard red winter wheats; ‘Advance’, ‘Steptoe’, ‘Lud’, ‘Pirolene’, and ‘Klages’ spring barleys (Hordeum vulgare L.); ‘Kamiak’, ‘Boyer’, and ‘Schuyler’ winter barleys; Waid durham wheat (Triticum durum Desf.); and ‘Flora’ and ‘Palouse’ triticales (Triticale hexaploide Lart.); were buried in field plots. The straw bags were removed at intervals during 1 yr and analyzed for the amount of decomposition, and C and N contents. Final decomposition ranged from 54% for the Borah wheat straw to 75% for the Lud barley straw with about half of the straws decomposing 64 or 65%. The hard red spring wheat and triticale straws decomposed the slowest and two spring barley straws decomposed most rapidly, but no completely systematic differences were observed for different genera of straws. The original straw N concentrations ranged from 2.2 to 12.5 g/kg. Nine straws lost N during the incubation period from September to November while eight increased in N concentration during this time. In the next three incubation periods, from November to the following October, nearly every straw sample increased in N concentration. The total N weight in the straw increased to the May sampling and then decreased thereafter. This pattern indicates that the straw was releasing N as it was mineralized and became available for utilization by the growing corn crop. Carbon/N ratios ranged widely in the initial straw samples, becoming more nearly uniform as the decomposition process developed. The C/N ratios remained fairly high avg 41 for the final sampling even though the straw in every case had released N into the soil during the last sampling period. Regression analysis of total decomposition and change in weight of N in the wheat straw samples for the first 67‐d incubation in the field showed a linear relationship with decomposition during the year, decreasing with increasing N loss in the early stage.

Root exudate carbon mitigates nitrogen loss in a semi-arid soil

“…Both DOC and LFOM are indicators of available C in soil, as these soil OM fractions are transient, turnover rapidly and are microbial substrates (Janzen et al, 1992;Haynes, 2005). In addition, cereal crop residues typically have C:N ratios ranging from 40:1e150:1 (Smith and Peckenpaugh, 1986;Singh et al, 2004;Hoyle and Murphy, 2011) so addition of residues to soil should also create an N immobilising environment, observed in the longterm by increased soil N retention in the build up plant residue treatment (þOM soil; Table 1). The amount of available C released during crop residue decomposition cannot however be explained by residue C:N ratio; the complex chemical composition of residues provides less available C than rhizodeposits, which are dominated by microbially available low molecular weight solutes such as sugars and amino acids (Kumar and Goh, 2000;Farrar et al, 2003).…”

Biological N2 fixation by heterotrophic and phototrophic bacteria in association with straw

“…Straws with higher N contents decompose more quickly than those containing less N (Zielinski, 1980) and when Smith and Peckenpaugh (1986) studied the decomposition of 23 cereal straws they found a direct correlation (r = + 0. Straws with higher N contents decompose more quickly than those containing less N (Zielinski, 1980) and when Smith and Peckenpaugh (1986) studied the decomposition of 23 cereal straws they found a direct correlation (r = + 0.…”

Breeding crops for reduced-tillage management in the intensive, rice–wheat systems of South Asia

“…Decomposition of retained residues is influenced primarily by the environment and management factors (Parr and Papendick 1978;Tanaka 1986) and to a minor extent by the species (Smith and Peckenpaugh 1986) and cultivar type (Summerell and Burgess 1989). Several workers reported differences in residue decomposition due to differences in N, C/ N, lignin/N, and polyphenol/N ratios, even for the same species (Kumar and Goh 2000).…”