Publications by Colleges and Departments (MSU - Bozeman)
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Item Changes in Biological Soil Health Properties in Response to Increased Crop Diversity in a Dryland Wheat-Based Cropping System(Informa UK Limited, 2024-08) Eberly, Jed O.; Hammontree, Jenni W.; Fordyce, Simion I.; Jones, Clain A.; Carr, Patrick M.Diversifying wheat (Triticum aestivum L.)-based cropping systems is important for the sustainability of dryland agriculture. Research has focused on the agronomic benefits of increased crop diversity in semi-arid environments, but less is known about the impacts of increased crop diversity on the soil microbial community. This work compared soil health parameters between a continuous wheat crop sequence to a diverse sequence that included pea (Pisum sativum L.), proso millet (Panicum miliaceum L.), safflower (Carthamus tinctorius, L.), and spring wheat. Respiration was higher (p < .005) in the diverse sequence while activity of N-acetyl-β-d-glucosaminidase was lower (p < .05) with a mean rate of 26.3 and 16.3 mg ρ-nitrophenol kg−1 soil h−1 for the continuous wheat and diverse sequences, respectively. The mean net nitrogen mineralized during the growing season was 33.2 ± 2.5 kg ha−1 and was not different between treatments (p > .05). No difference was observed in bacterial alpha diversity, while fungal community diversity was 52% lower in the diverse rotation. The results of this work suggest that specific crops in a rotation may impact microbial processes related to nitrogen mineralization and that the soil fungal community may be more sensitive to changes in crop sequence than the soil bacterial community.Item Long‐term cover crop effects on biomass, soil nitrate, soil water, and wheat(Wiley, 2023-05) Miller, Perry R.; Jones, Clain A.; Zabinski, Catherine A.; Tallman, Susan M.; Housman, Megan L.; D'Agati, Kristen M.; Holmes, Jeffrey A.Cover crops during summer fallow have been rarely researched in the semiarid northern Great Plains. This study was conducted during 2012–2019 at four Montana locations and included four functional groups (Brassica family, fibrous-rooted crops, legumes, and tap-rooted crops). Eleven treatments included sole functional groups, a Full Mix, the Full Mix minus each functional group, pea, and chemical fallow. Wheat (Triticum aestivum L.) was grown after each cover crop year with three nitrogen (N) fertilizer rates. Cover crops were terminated with herbicide at first flower stage of pea (Pisum sativum L.) 57 to 66 days after planting. Shoot biomass averaged 2.0 Mg ha−1 over eight site-years representative of dryland farming in Montana. Using equal overall plant densities, treatments with six species averaged 13% greater biomass than two species. Measured at termination to a 0.9-m depth, Fallow held greater soil water than cover crop treatments, with Fallow averaging 57 mm greater than the Full Mix. Soil nitrate averaged 49 kg N ha−1 greater after Fallow than the Full Mix; the Legume treatment averaged 26 kg N ha−1 greater than the Minus Legume treatment. Wheat yield on Fallow averaged 0.85 Mg ha−1 greater than the Full Mix in 5 of 10 site-years, mainly at the driest site-years. The Legume treatment elevated wheat protein over the Minus Legume treatment by an average of 15 g kg−1. Cover crops grown during summer fallow reduced soil nitrate-N, soil water, and wheat yields compared with chemical fallow, especially in the major wheat growing region of north central Montana.Item Water and nitrate loss from dryland agricultural soils is controlled by management, soils, and weather(2020-12) Sigler, W. Adam; Ewing, Stephanie A.; Jones, Clain A.; Payn, Robert A.; Miller, Perry R.; Maneta, Marco P.The vast majority (82 %) of the earth’s cultivated area is not irrigated, and half is in semi-arid regions where water tends to limit crop growth. In dryland semi-arid agroecosystems, any precipitation not transpired indicates crop yield that is below potential. Precipitation that is partitioned to deep percolation can transport nitrate out of the root zone, reducing nitrogen use efficiency and potentially contaminating groundwater. To mitigate loss of crop yield to drought, the practice of chemical summer-fallow (suppressing plant growth for a full growing season with herbicide) has been common in semi-arid regions to store water for the following growing season. However, precipitation losses during fallow tend to exceed the amount of precipitation stored, and fallow tends to increase nitrate leaching. We present model simulations informed by field observations that explore the interaction of crop rotation, weather, and soils as controls on precipitation partitioning and nitrate leaching. Simulations reveal that high intensity precipitation periods produce hot moments of deep percolation and nitrate leaching such that 54 % of deep percolation and 56 % of leaching occurs in two of 14 model years. Simulations indicate that thin soils (having limited water storage capacity) produce hot spots for deep percolation and nitrate leaching such that thinner soils (<25 cm) experience water and nitrate loss rates five to 16 times higher than thicker soils (>100 cm). The practice of fallow facilitates mineralization of soil organic nitrogen to nitrate and increases deep percolation, magnifying the interaction of hot moments and hot spots. Simulations suggest that a field with fallow in rotation once every three years experiences 55 % of its deep percolation and 43 % of its leaching losses during fallow years.