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United States Department of Agriculture

Agricultural Research Service

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Research Project: Improved Soil Managment Practices for Tilled Summer Fallow in the Pacific Northwest

Location: Soil and Water Conservation Research

2013 Annual Report


1a.Objectives (from AD-416):
1.)Apply new findings on erosion-resistant and water-use-efficient tillage techniques for summer fallow regions of the Pacific Northwest and develop prescriptions for efficient tillage timing.1a.) Measure the performance of coarse summer fallow mulches in on-farm tests, get feedback from farmers, and recommend best tillage practices. 1b.) Identify the optimal timing for creation of a reduced-tillage fallow mulch in the lower precipitation (<350 mm) winter wheat-fallow region and determine if it can be predicted using soil water, temperature, or weather forecasts, and if it is different from the timing farmers already use. 1c.) Predict where early seeding is not necessary from maps of growing degree days following fall precipitation. 2.)Identify dryland cropping systems in the Pacific Northwest capable of maximizing C sequestration and greenhouse gas (GHG) mitigation. 2a.) Identify dryland cropping systems in the Pacific Northwest capable of maximizing carbon sequestration and greenhouse gas mitigation through measurement of soil organic carbon changes and N_2O and CH_4 fluxes in long-term experiments. 2b.) Make projections of CO_2 emissions and soil organic carbon after changes in tillage and cropping system utilizing the CQESTR model.


1b.Approach (from AD-416):
1a.) Soil mulch types from coarse to fine will be compared for their ability to preserve stored soil water. These comparisons will take place for at least three years in small plot experiments on three experiment stations, and in three farmers’ fields in on-farm tests. 1b.) Untilled fallow soil will be continuously monitored during the late winter and spring using electronic moisture and temperature probes. Small plots tilled at intervals over spring and early summer will be measured for stored soil water to determine if moisture and temperature probes plus historic weather data is enough to predict optimal tillage timing. 1c.) Data comparing the difference in yield between early and late emerging winter wheat in different years at many locations will be compiled to see if it correlates with growing degree days available for the development of late-emerging wheat. 2a.) Pacific Northwest cropping systems will be examined in intermediate precipitation zone (425 mm) experiments. Gas samples (CO_2, N_2O, and CH_4) will be collected from selected treatments for three years. Total C, N, and S, extractable P and K, labile C and N fractions, pH, EC, bulk density and wet aggregate stability will be determined. 2b.) The CQESTR model will be used to make predictions of soil organic carbon change and CO_2 emissions and assess the impact of management practices on soil organic matter in reduced tillage fallow and other dryland cropping systems. Replacing 5356-11120-002-00D (07/2011).


3.Progress Report:
Progress was made on each objective for the Project 5356-11120-003-00D, which started October 2011. The tillage mulch data revealed that initial tillage could be delayed and still achieve good seed-zone moisture for late summer seeding of wheat. Data on evaporation from different types and depths of soil mulch and different amounts of surface residue indicated that measureable differences exist and that response to rainfall may be as important as response to evaporation. Methods were refined and are being repeated. Data were collected from moisture and temperature sensors in the continuous chemical-fallow plots. Data collection has gone smoothly at two of the three sites. Ongoing problems with rodents have led to substantial data gaps in the third site, but we now believe we have solved those problems.

We examined growing-degree data and discussed the possibilities of using large data sets from NOAA and University of Washington to model this project. We also had a discussion with the Oregon State University (OSU) climate center about this project and agreed that a full analysis would be worthwhile, resources permitting. We determined that on-farm testing will not add significantly to the information supplied by NOAA, University of Washington, and the OSU climate center.

Greenhouse gas samples were collected and nitrous oxide, carbon dioxide, and methane levels were determined. Soil analysis is progressing and the Greenhouse Gas Reduction through Agricultural Carbon Enhancement network (GRACEnet) database is now populated with most of the initial soil properties. Crop yields to date have been entered. These efforts also contributed to Renewable Energy Assessment Project (REAP) database development. We helped other GRACEnet/REAP sites with data entry and quality control to prepare for public release.


Review Publications
Gollany, H.T., Fortuna, A., Samuel, M., Young, F.L., Pan, W., Pecharko, M. 2013. Soil organic carbon accretion vs. sequestration using physicochemical fractionation and CQESTR simulation. Soil Science Society of America Journal. 77:618-629.

Wuest, S.B., Gollany, H.T. 2012. Soil organic carbon and nitrogen after application of nine organic amendments. Soil Science Society of America Journal. 77(1):237-245.

Wuest, S.B. 2013. An array for measuring detailed soil temperature profiles. Soil Science Society of America Journal. 77(2):427-431.

Plaza, C., Gollany, H.T., Baldoni, G., Polo, A., Ciavatta, C. 2012. Predicting long-term organic carbon dynamics in organically-amended soils using the CQESTR model. Journal of Soils and Sediments. 12:486-493.

Last Modified: 9/29/2014
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