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Crop rotations in the northern Great Plains of North America increasingly include corn (Zea mays L.) and soybean (Glycine max (L.) Merr.). Use of cover crops, while less extensive, is also increasing given their purported agronomic and environmental benefits. To date, soil responses to the inclusion of corn, soybean, and cover crops in rainfed cropping systems have not been well documented in the region. Therefore, soil properties were evaluated 6 years after establishment of three crop rotations (spring wheat (Triticum aestivum L.)–soybean (SW–S), spring wheat–corn–soybean (SW–C–S), and spring wheat–corn–cover crop (SW–C–cc)) each split by no and minimum tillage on a Dark Brown Chernozem near Mandan, ND, USA. Soil responses to treatments were subtle and exclusive to the 0–7.6 cm depth. Soil pH was lower in SW–S than SW–C–cc (5.28 vs. 5.48; P = 0.05), SO4-S was greater under SW–C–cc than SW–C–S (13.4 vs. 11.6 g S kg−1; P = 0.03), exchangeable K was greater under SW–C–S and SW–C–cc than SW–S (0.83 cmol kg−1 vs. 0.52 cmol kg−1; P = 0.05), and water-stable aggregates were greater in SW–S than SW–C–S (26% vs. 19%; P = 0.08). Soil organic carbon (SOC) and total N did not differ among crop rotations or between tillage treatments, while particulate organic matter N was greater under no tillage compared to minimum tillage (P = 0.08). Between 2012 and 2018, soil pH decreased and SOC increased under SW–C–S. Frequent monitoring of near-surface soil conditions in rotations with soybean every other year is recommended. Furthermore, innovative management practices are needed to enhance soil C and N fractions in rotations with full-season cover crops. [ABSTRACT FROM AUTHOR]

During periods of no or low crop growth in dryland cropping systems, tillage can reduce residue coverage and thereby elevate wind erosion risk. We measured wind erosion on a silt loam, Haplustoll soil in North Dakota (456 mm precipitation yr–1) in response to levels of tillage applied once in spring during fallow following a small grain–sunflower (Helianthus annuus L.) rotation. Treatments were no‐tillage (NT), one‐pass tandem disk tillage (TDT), and two‐pass offset disk tillage (ODT). Erosion flux was measured with sediment samplers near peripheries of >1‐ha replicated plots from May through September 2003 and 2004. Soil losses in ODT, TDT, and NT were 12.0, 4.8, and 2.1 Mg ha–1, respectively, in 2003 and 2.6, 1.6, and 1.4 Mg ha–1 in 2004. The greatest loss, 12.0 Mg ha–1, was equivalent to 1‐mm soil depth. The two‐ to fivefold greater erosion in 2003, a year with 2 mo of <30% of average precipitation, appears linked to a decline in residue coverage. Coverage remained about the same in NT and increased in tilled treatments during 2004 with more average precipitation. Our measurements of wind erosion have shown how the residue‐destroying effects of a single tillage event can be considerably exacerbated by a moderate, seasonal drought. This indicates the critical importance of NT for limiting soil and residue disturbance and reducing wind erosion risk from drought‐affected plant growth failure in semiarid cropping systems. Core Ideas: Wind erosion loss was two‐ to sixfold greater under disk tillage than no‐tillage.Seasonal drought led to less weed growth and residue coverage.Seasonal drought resulted in two‐ to fivefold greater wind erosion loss.The Revised Wind Erosion Equation (RWEQ) model indicated that residue coverage conferred the greatest resistance to erosion. [ABSTRACT FROM AUTHOR]

Long-term use of nitrogen (N) fertilizers can lead to fertility-lowering soil chemical changes. To examine this in geologically young soils in the northern Great Plains of North America, we present near-surface (0–7.6 cm) soil chemistry data from 16 years of two crop rotations: continuous crop (CC; spring wheat [Triticum aestivumL.]—winter wheat [T. aestivum]—sunflower [Helianthus annuusL.]) and crop-fallow (C-F; spring wheat—fallow) that underwent factorial tillage (none, minimum, conventional) and N rate (low, medium, high) treatments. For CC, the N rate (but not tillage) had a significant effect on pH, with the high N rate leading to the largest pH decline (−0.76). The nitrogen rate also had a significant effect on cation exchange capacity (CEC) for CC, whereby CEC increased with the N rate. Managers utilizing high N rates should be aware of the potential for soil acidification, even in the northern Great Plains of North America. [ABSTRACT FROM AUTHOR]

Emphasis is placed on developing robust, productive, economically competitive, and environmentally benign agroecosystems. In 2012, after 18 yr of a study to evaluate the effects of crop sequence and tillage, we measured soil properties at various depths to 91.4 cm and estimated soil C. The experiment, near Mandan, ND, was a split-plot design, with crop sequence as whole plots and tillage (minimum tillage or no-till) as subplots. Crop sequences included continuous spring wheat (Triticum aestivum L.) with crop residue retained or removed, spring wheat--millet [Setaria italica (L.) Beauv.], spring wheat--safflower (Carthamus tinctorius L.)--fallow, spring wheat--safflower--rye (Secale cereale L.) and spring wheat--fallow. Soil organic C, calculated by the equivalent mass method (SOCem), was consistently higher (P < 0.001) than when calculated by the fixed-depth method. Disparities between the two methods, greatest near the soil surface, were attributable to tillage. Estimates of SOCem were not affected by cropping sequence at any depth, averaging about 26, 47, 73, 114 and 156 Mg ha-1 in the 0- to 7.6-, 0- to 15.2-, 0- to 30.5-, 0- to 61.0-, and 0- to 91.4-cm partitions. Tillage had no influence at depths <30.5 cm, but no-till plots contained more SOCem than minimum tillage plots in the 0- to 61-cm (115 vs. 112 Mg ha-1 ) and 0-to 91.4-cm (158 vs. 153 2.3 Mg ha-1 ) partitions (P < 0.05). Soil organic C in the 0-to 7.6-cm depth increased by an average of 3.2 Mg ha-1 or 16% since 2001. This study suggests that C sequestration in soil is less impacted by the choice of crop sequence than by tillage. [ABSTRACT FROM AUTHOR]

The potential for mitigating increasing atmospheric carbon dioxide concentrations through the use of terres-trial biological carbon (C) sequestration is substantial. Here, we estimate the amount of C being sequestered by natural processes at global, North American, and national US scales. We present and quantify, where possible, the potential for deliberate human actions - through forestry, agriculture, and use of biomass-based fuels - to augment these natural sinks. Carbon sequestration may potentially be achieved through some of these activities but at the expense of substantial changes in land-use management. Some practices (eg reduced tillage, improved silviculture, woody bioenergy crops) are already being implemented because of their economic benefits and associated ecosystem services. Given their cumulative greenhouse-gas impacts, other strategies (eg the use of biochar and cellulosic bioenergy crops) require further evaluation to determine whether widespread implemen-tation is warranted. INSET: In a nutshell:. [ABSTRACT FROM AUTHOR]

The article discusses research which examined possible impact of agricultural management practices which include irrigation, tillage and nitrogen (N) fertilization on soil greenhouse gas (GHG) emissions in the U.S. It is said that irrigation can increase both carbon dioxide and N dioxide emissions unlike strategies which include increasing soil water availability and microbial activity. It reports experimental procedures conducted which include measurement of soil GHG fluxes and application of N fertilizers. The use of the Analysis of Repeated Measures technique for evaluating soil temperature and water content is also noted.