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Research Project: Development of Ecologically-Sound Pest, Water and Soil Management Practices for Northern Great Plains Cropping Systems

Location: Agricultural Systems Research

2018 Annual Report

1. Cover crops replace fallow in semi-arid durum cropping systems. The traditional 2-yr rotation of spring wheat followed by summer fallow helps decrease the risk of crop failure in the short term, but long-term consequences include soil carbon depletion, formation of saline-seeps, degraded environment for soil microbiology, loss of habitat for fauna including pollinating insects, reduced soil water holding capacity, and inefficient precipitation storage during fallow with about 60 to 85% of precipitation lost to surface evaporation. Interest among wheat growers in utilizing diverse cover crop mixtures to enhance soil quality is increasing but the lack of immediate financial return on the cost of seeding a traditional cover crop discourages many growers from adopting this practice. However, little is known about replacing the fallow phase in wheat-fallow rotations, for example with a multispecies crop harvested for forage with regrowth left to serve as a standing cover crop. ARS researchers in Sidney, Montana initiated a 6-year study to investigate the production potential of a 10 species crop mix (buckwheat, canola, cowpea, flax, lentil, millet, pea, radish, sorghum, turnip) in place of fallow in 2-year durum rotations. Results from the first 3-year period of the study indicate planting a multispecies crop mix in place of fallow provided on average 1.4 tons per acre (59% of which was radish and pea) of high-quality forage harvested in early summer and an additional 2.4 tons per acre (50% of which was sorghum and millet) unharvested biomass at killing frost left for standing cover to increase ecosystem services compared to fallow. Results from this research show that utilizing a portion of the cover crop growth as forage may offset seeding costs enough to make adoption more economical.

2. Smart soil moisture sensors for irrigation scheduling. Better irrigation scheduling is one of the most critical aspects of irrigated agriculture for improving yield and reducing the adverse impact on quality of surface and ground waters. In team research, ARS scientists in Sidney, Montana conducted a field study at two locations of different soil texture, one in North Dakota and the other in Montana. Their goal was to evaluate HydraProbe, Campbell Time Domain Reflectometry and Watermark real-time soil moisture sensors for their ability to estimate water content in sandy loam and clay loam soils. Results showed that the three sensors provided different estimates of soil moisture contents in both soils. Nevertheless, their work suggests that soil moisture sensors including those used in this study can be suitable for irrigation scheduling without in-situ calibrations by simply setting the upper and lower irrigation trigger limits for each sensor and each soil type. The upper trigger point occurs directly after an irrigation event and the lower trigger point is based on about 50% depletion of available water in the crop root zone and it occurs prior to irrigation refill. This approach can help irrigators to achieve their irrigation scheduling and productivity goals without consuming any time on sensor calibration. The approach requires minimal training and labor, and it can provide useful information to aid producers to determine when and how much to irrigate without causing any damage to their crops, thereby optimizing crop productivity while maintaining environmental quality with minimal water loss.

3. Diversified crop rotation and improved management enhance pea yield and water use. Continuous cropping allows dryland farmers to better utilize the limited amount of precipitation in the semi-arid northern Great Plains. However, the crop chosen to replace the fallow phase must leave enough moisture in the soil for the wheat crop grown during the following year. Cool-season pulse crops such as pea and lentil are planted in early spring and mature in early summer allowing the soil to accrue moisture from late summer rains that would be removed by longer-season crops. Pea has been grown to replace fallow in the wheat-fallow system and has been a particularly good fit in arid and semiarid regions, but growers need more information about best management practices that enhance dryland pea yield and water-use efficiency. ARS researchers at Sidney, Montana found that a longer crop rotation with non-legumes and increased seeding rate and wheat stubble height enhanced pea yield and water use efficiency compared to a shorter crop rotation and conventional seeding rate and stubble height. Research from this research will help producers increase dryland pea yield by efficiently utilizing soil water using extended crop rotations with non-legumes and by increasing seeding rate and stubble height.

4. Carbon sequestration and nitrogen balance vary with crop rotations. Soil carbon content is an important indicator of soil health and represents a reservoir of sequestered carbon that can lessen the impact of increase C-based greenhouse gas emissions to the atmosphere. Nitrogen can also can be lost to the environment through various pathways and cam be a source of greenhouse gases. It is vital to agricultural producers and non-producers alike that we understand how agricultural practices affect soil carbon sequestration and nitrogen balance, especially in the in the northern Great Plains where little carbon sequestration research has been conducted. ARS scientists in Sidney, Montana reported that soil carbon sequestration increased with continuous non-legume or a two-year rotation of a legume and non-legume crop compared to more diversified, extended crop rotations. In contrast, diversified legume-based rotations reduced nitrogen fertilization rate, increased crop nitrogen uptake, reduced nitrogen loss to the environment, and enhanced nitrogen surplus compared to continuous non-legume monocropping. A two-year rotation of legume-non-legume crops can enhance soil carbon and nitrogen sequestration, increase crop nitrogen uptake, optimize nitrogen balance, and reduce external nitrogen inputs compared to non-legume monocropping. Previous research has shown that rotating a non-legume such as wheat with an annual legume such as pea improves system productivity and water-use efficiency. This new research shows that this cropping system also improves carbon sequestration and nitrogen balance resulting in enhanced soil quality and reduced environmental impacts.

5. Direct-seeded sugar offers lower input costs and protection from soil erosion. Increased labor and tillage costs during the past decade have led to greater interest in reduced tillage among sugar beet growers. Direct-seeding, where seed is planted without any preplant tillage, offers potential cost and soil conservation benefits but greater challenges as well. ARS scientists in Sidney, Montana found that direct seeding led to more uniform seedling emergence, which was likely the result of better soil moisture during germination. However, sucrose yield was 10-15% lower with direct seeding than with intensive tillage in three of five years. In the other two study years, yield was unaffected by tillage or rotation diversity. The lower yield in some years may be attributable to slower early season growth which in turn leads to slower development of a full crop canopy and less interception of solar radiation. Soil temperature was from 3 to 12 °C cooler with direct seeding than with intensive tillage during the critical emergence and seedling growth periods. These cooler soil temperatures may have reduced mineralization of soil organic nitrogen and caused early season nutrient deficiency. If this negative effect on early season growth can be overcome, direct seeding could provide comparable yields compared to conventional practices with much lower fuel and labor costs and better protection against soil degradation.

Review Publications
Sainju, U.M., Allen, B.L., Lenssen, A.W., Mikha, M.M. 2017. Root and soil total carbon and nitrogen under bioenergy perennial grasses with various nitrogen rates. Biomass and Bioenergy. 107(12):326-334.
Sainju, U.M., Singh, H.P., Singh, B.P., Whitehead, W.F., Chiluwal, A., Paudel, R. 2018. Cover crop and nitrogen fertilization influence soil carbon and nitrogen under bioenergy sweet sorghum. Agronomy Journal. 110(2):463-471. .
Jabro, J.D., Iversen, W.M., Stevens, W.B., Allen, B.L., Sainju, U.M. 2017. A new automated passive capillary lysimeter for logging real-time drainage water fluxes. Applied Engineering in Agriculture. 33(6):849-857. doi:10.13031/aea.12433.
Jabro, J.D., Stevens, W.B., Iversen, W.M. 2017. Field performance of three real-time moisture sensors in sandy loam and clay loam soils. Archives of Agronomy and Soil Science. 64(7):930-938.
Sainju, U.M., Lenssen, A.W., Allen, B.L., Stevens, W.B., Jabro, J.D. 2017. Soil total carbon and nitrogen and crop yields after eight years of tillage, crop rotation, and cultural practice. Heliyon. 3:e00481.
Sainju, U.M., Lenssen, A.W., Allen, B.L., Stevens, W.B., Jabro, J.D. 2018. Nitrogen balance in dryland agroecosystem in response to tillage, crop rotation, and cultural practice. Nutrient Cycling in Agroecosystems. 110:467-483.
Wang, J., Fu, X., Zhao, F., Sainju, U.M. 2018. Response of soil carbon fractions and dryland maize yield to mulching. Soil Science Society of America Journal. 82(2):371–381. .
Nash, P.R., Gollany, H.T., Sainju, U.M. 2018. CQESTR simulated response of soil organic carbon to management, yield, and climate change in northern Great Plains region. Journal of Environmental Quality. 47:674-683.
Wang, J., Fu, X., Sainju, U.M., Fazhu, Z. 2018. Soil carbon fractions in response to straw mulching in the Loess Plateau of China. Biology and Fertility of Soils. 10:ply020.
Sainju, U.M. 2018. Agricultural management impact on greenhouse gas emissions. In: Rao, C.S., Shankar, A.K., and Shanker, C., editors. Climate Resilient Agriculture - Strategies and Perspectives. Rijeka, Croatia: InTech Publication. p. 89-103.
Lenssen, A.W., Sainju, U.M., Jabro, J.D., Allen, B.L., Stevens, W.B. 2018. Dryland pea production and water use responses to tillage, crop rotation, and weed management practice. Agronomy Journal. 110(5):1843-1853.
Sainju, U.M., Singh, H.P., Singh, B.P., Chiluwal, A., Paudel, R. 2018. Soil carbon and nitrogen under bioenergy forage sorghum influenced by cover crop and nitrogen fertilization. Agrosystems, Geosciences & Environment. 1:180004.
Wang, J., Ghimire, R., Fu, X., Sainju, U.M., Wenzhau, L. 2018. Straw mulching increases precipitation storage rather than water use efficiency and dryland winter wheat yield. Agricultural Water Management. 206:95-101.
Chiluwal, A., Singh, H.P., Sainju, U.M., Khanal, B., Whitehead, W.F., Singh, B.P. 2018. Spacing effects on energy cane growth, physiology, and biomass yield. Crop Science. 58(3):1371-1384.
See Log #350966 for correct journal entry. This entry is for Abstract #111516 oral presentation at ASA-CSSA meeting in Baltimore, MD and SSSA meeting in San Diego, CA.