Location: Northwest Irrigation and Soils Research
Project Number: 2054-12000-013-001-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Jul 1, 2020
End Date: Jun 30, 2025
Objective:
The overall objective of the study is to investigate a wide-range of cereal grain residue carbon, nitrogen, and mineral balances and investigate decomposition characteristics.
Objective 1 to determine breakdown dynamics of cereal straw at multiple residue rates and fertilizer N rates under controlled laboratory conditions.
Objective 2 is to utilize straw (i.e., barley/corn/wheat) in-field to determine breakdown of residues from application time until late in the season under various fertilizer-N levels and with surface and sub-surface application.
Objective 3 is to conduct an initial survey of cereal grain crops (i.e., barley/corn/wheat) to assess the variation in C:N ratios and mineral content at selected locations.
Objective 4 – Conduct field studies on residue management impacts on barley yield/quality and soil response under tilled and no-till conditions with both retention and removal of residue.
Objective 5 – Conduct residue decomposition studies of barley/wheat during the next barley crop (yield and quality measured) under irrigated conditions from harvest to harvest under several N levels.
Approach:
This funding is part of a multi-year project and represents year 3 of 3 of the study.
1) Barley, corn and/or wheat will be grown and collected to produce residue for column experiments in the laboratory to determine nutrient cycling. Laboratory experiments allow direct comparison of different plant residues under controlled conditions, thus, allowing conclusions to be made concerning rates of breakdown between different plant residues without the influence of environmental factors that may impact results.
2) Straw (i.e., barley, corn, wheat) will be added to non-reactive bags and applied to selected field locations in the fall under multiple fertilizer-N rates and at both surface and sub-surface depths. Decomposition will be determined at set intervals from the fall through the end-of-season. Samples will be collected to determine soil nutrient status.
3) An initial survey will be conducted of cereal straw to determine C:N ratios at multiple locations in Idaho. Cereals will be consistent between the study locations and will represent a range of locations and management practices. Cereal samples will be collected prior to harvest to determine straw C:N ratios as well as biomass production and mineral content that is important for estimating the potential straw return (i.e., tons/acre) from yield levels. This will increase the understanding of the degree of variability of C:N ratios and mineral content both between crops (barley/corn/wheat) and within crops.
4) The study will be located at the NWISRL research farm. The study will be comprised of two crop rotations, two tillage practices, and two residue management strategies representative of common practices in the region. The treatments will be 1) barley - barley and 2) wheat - barley, conventional (disk, roller harrow, and chisel plow) reduced tillage (no-till barley and wheat) and removed and retained residue management treatments. Fertilizer and crop management will be based on University of Idaho extension guidelines. Barley and wheat will be planted and harvested for grain. In the residue removed treatments, a forage harvester will remove the residue remaining in the field after grain harvest. All crop residue will remain on the plots for the residue retained treatment. In the next season barley will be grown and yield and quality response determined.
Residue bags and small plot areas will be segregated from a section of the larger plots described above to allow 3 fertilizer rates to be applied and residue decomposition bags to be installed. Procedures will mirror those in previous studies used for a study of residue breakdown rate from fall to spring. This study will improve our understanding of the impact of applied fertilizer N to facilitate breakdown by investigating residue breakdown under in-field conditions and pairing that with barley crop response from both variations in residue management and fertilizer applications.
