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Soil Organic Carbon Dynamics in the Pendleton Long‐Term Experiments: Implications for Biofuel Production in Pacific Northwest
Author(s) -
Machado Stephen
Publication year - 2011
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj2010.0205s
Subject(s) - tillage , soil carbon , crop residue , agronomy , straw , plough , crop rotation , sativum , conventional tillage , manure , environmental science , long term experiment , green manure , soil water , chemistry , zoology , fertilizer , crop , biology , soil science , agriculture , ecology
Use of crop residues for biofuel production raises concerns on how removal will impact soil organic carbon (SOC). Information on the effects on SOC is limited and requires long‐term experimentation. Fortunately, Pendleton long‐term experiments (LTEs), dating to the 1930s, provide some answers. This study compared crop residue inputs and SOC balance in conventional tillage (CT) winter wheat ( Triticum aestivum L.)–summer fallow (WW‐SF) systems with annual rotation of WW and spring pea ( Pisum sativum L.). The WW‐SF consisted of crop residue (CR‐LTE) (0–90 N ha −1 yr −1 , 11.2 Mg ha −1 yr −1 of steer ( Bos taurus ) manure and 1.1 Mg ha −1 yr −1 of pea vines additions, residue burning, and tillage fertility (TF‐LTE) (tillage‐ plow, disc, sweep, and N (0–180 kg ha −1 )). Winter wheat–pea (WP‐LTE) rotation treatments included maxi‐till (MT‐disc/chisel), fall plow (FP), spring plow (SP), and no‐till (NT). Soils were sampled (0–60‐cm depth) at 10‐yr intervals, and grain yield and residue data collected every year. In WW‐SF systems, SOC was maintained only by manure addition and depleted at a rate of 0.22 to 0.42 Mg ha −1 yr −1 in other treatments. In WP‐LTE, MT, FP, SP, and NT treatments increased SOC at the rate of 0.10, 0.11, 0.02, and 0.89 Mg ha −1 yr −1 , respectively. Minimum straw biomass to maintain soil organic carbon (MSB) in the CR‐LTE, TF‐LTE, and WP‐LTE was 7.8, 5.8, and 5.2 Mg ha −1 yr −1 , respectively. Winter wheat‐SF straw production was lower than MSB, therefore residue removal exacerbated SOC decline. Harvesting straw residues under NT continuous cropping systems is possible when MSB and conservation requirements are exceeded.