Soil salinity is a global issue threatening land productivity, and estimates predict that 50% of all arable land will become impacted by salinity by 2050. Consequently, it is important to have a fundamental understanding of crop response to salinity to minimize economic loss and improve food security. While an immense amount of research has been performed assessing corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] response to salinity, there are few, if any, comprehensive reviews compiling previously published literature. This review provides a detailed description of our current knowledge on the impacts of salinity on corn and soybean growth and development. Both osmotic stress and specific ion toxicities with respect to corn and soybean are addressed. Additionally, potential areas of future research are recommended.Core Ideas Review of salinity's effects on corn and soybean growth and development. Impacts of osmotic stress and specific ion toxicities discussed. Potential areas of future research addressed.

Soil-water evaporation is important at scales ranging from microbial ecology to large-scale climate. Yet routine measurements are unable to capture rapidly shifting near-surface soil heat and water processes involved in soilwater evaporation. The objective of this study was to determine the depth and location of the evaporation zone within soil. Three-needle heat-pulse sensors were used to monitor soil heat capacity, thermal conductivity, and temperature below a bare soil surface in central Iowa during natural wetting/drying cycles. Soil heat flux and changes in heat storage were calculated from these data to obtain a balance of sensible heat components. The residual from this balance, attributed to latent heat from water vaporization, provides an estimate of in situ soil-water evaporation. As the soil dried following rainfall, results show divergence in the soil sensible heat flux with depth. Divergence in the heat flux indicates the location of a heat sink associated with soil-water evaporation. Evaporation estimates from the sensible heat balance provide depth and time patterns consistent with observed soil-water depletion patterns. Immediately after rainfall, evaporation occurred near the soil surface. Within 6 days after rainfall, the evaporation zone proceeded > 13 mm into the soil profile. Evaporation rates at the 3-mm depth reached peak values > 0.25 mm h −1 . Evaporation occurred simultaneously at multiple measured depth increments, but with time lag between peak evaporation rates for depths deeper below the soil surface. Implementation of finescale measurement techniques for the soil sensible heat balance provides a new opportunity to improve understanding of soil-water evaporation. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. ABSTRACT Soil-water evaporation is important at scales ranging from microbial ecology to large-scale climate. Yet routine measurements are unable to capture rapidly shifting near-surface soil heat and water processes involved in soil-water evaporation. The objective of this study was to determine the depth and location of the evaporation zone within soil. Three-needle heat-pulse sensors were used to monitor soil heat capacity, thermal conductivity, and temperature below a bare soil surface in central Iowa during natural wetting/ drying cycles. Soil heat flux and changes in heat storage were calculated from these data to obtain a balance of sensible heat components. The residual from this balance, attributed to latent heat from water vaporization, provides an estimate of in situ soil-water evaporation. As the soil dried following rainfall, results show divergence in the soil sensible heat flux with depth. Divergence in the heat flux indicates the location of a heat sink associated with soil-water evaporation. Evaporation estimates from the sensible heat balance provide depth and time patterns consistent with observed soil-water depletion patte...

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A growing world population and climate change are expected to influence future agricultural productivity and land use. This study determined the impact of land‐use change on soil sustainability and discussed the factors contributing to these changes. South Dakota was selected as a model system because corn (Zea mays L.) grain prices tripled between 2006 and 2012 and it is located in a climate and grassland/cropland transition zone. High resolution imagery was used to visually determine land uses (cropland, grassland, nonagricultural, habitat, and water) at 14,400 points in 2006 and 2012. At each point, land‐use change and the USDA land capability class (LCC) were determined. Over the 6‐yr study period, 6.87% of the grasslands (730,000 ha) were converted to cropland, with 93% occurring on lands generally considered suitable for crop production (LCC ≤ IV) if appropriate practices are followed. Converted grasslands, however, had higher LCC values than existing croplands and lower LCC values than remaining grasslands. In addition, 4.2% of the croplands (250,000 ha) were converted to grasslands, and statewide, 20,000 ha of croplands were converted to grasslands in areas limited by excess water (LCC V). The conversion of grasslands could not be linked to one specific factor and may be related to: (i) a desire to increase financial returns, (ii) changes in the land ownership structure, (iii) technology improvements, (iv) governmental policies, (v) climate change, and (vi) an aging workforce. Research and outreach programs that balance the goods and services of different land uses are needed to maintain sustainable agroecosystems.

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Core Ideas Nitrogen availability and fertilization can increase sunflower see yield.Nitrogen fertilization may decrease oil concentration of oilseed sunflower.Nitrogen fertilization increases sunflower lodging risk in windy regions. The N and P recommendations for sunflowers growers in North Dakota have not been changed in 30 yr. Twenty‐two N and P rate experiments were conducted during 2014 and 2015. The objective was to determine the response of seed yield, oil concentration, and lodging to available N and P. In 2014 studies were a randomized complete block split plot with N rate as main plots and P rate as subplots. Nitrogen was applied at rates of 0, 45, 90, 134, 179, and 224 kg N ha−1. Phosphorus was applied to establish P rates of 0, 13, 26, and 39 kg P ha−1. In 2015, the field design included only 0 and 26 kg P ha−1. Experiments were taken to yield and lodging was recorded at harvest. Oil seed sunflower (17 experimental locations) was also analyzed for oil concentration. The N response of sunflower seed yield was quadratic. Increased N rate resulted in lower oil concentration in half of the oilseed experiments. Increased N rate was linearly related to increasing lodging at several sites. Phosphate fertilization had little effect on seed yield, oil concentration, and lodging, despite many of the sites having soil P levels considered ‘low’. Future N rate recommendations should be based on seed yield response with increasing N and oil concentration reduction with increasing N for oilseed sunflower. A limit to maximum N rate should also be considered because of the lodging risk in this wind‐plagued region.

Seepage losses from animal‐waste lagoons can affect ground water quality, if facilities are not properly sited, designed, and constructed. Most states in the Great Plains stipulate that earthen lagoons cannot seep more than some specified rate (mm d−1). These criteria often apply to the entire state and all livestock species, although ground water vulnerability and waste characteristics are highly variable from site to site. Because of this variability, statewide “blanket” regulations may overregulate some producers and underregulate others. Furthermore, wide disparity exists in seepage allowances among neighboring states, and regulations often are influenced by public opinion rather than scientific findings. This paper argues that lagoon design should be site specific and presents a logical framework to determine the maximum allowable seepage rate for a given location and type of operation (e.g., dairy, swine, cattle feedlot). Site‐specific factors, such as soil properties, depth to water table, and chemistry of the waste, are used to arrive at lagoon performance standards that minimize long‐term risk. The decision process within the framework is presented as a conceptual model for lagoon permitting and may need to be customized to meet the requirements of each state. Nevertheless, use of site‐specific design criteria will ensure that manure storages are adequate (e.g., plastic‐lined lagoons) in regions with vulnerable ground water, while providing reduced lagoon construction costs (lower cost of soil‐lined lagoons) for producers who site their operations in areas of low risk. To complement the site‐specific approach, the whole‐lagoon seepage rate should be measured after construction to verify that the prescribed performance criteria have been met.

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