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Aquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ∼50% of groundwater depletion in the United States since 1900. A newly developed High Plains recharge map shows that high recharge in the northern High Plains results in sustainable pumpage, whereas lower recharge in the central and southern High Plains has resulted in focused depletion of 330 km3 of fossil groundwater, mostly recharged during the past 13,000 y. Depletion is highly localized with about a third of depletion occurring in 4% of the High Plains land area. Extrapolation of the current depletion rate suggests that 35% of the southern High Plains will be unable to support irrigation within the next 30 y. Reducing irrigation withdrawals could extend the lifespan of the aquifer but would not result in sustainable management of this fossil groundwater. The Central Valley is a more dynamic, engineered system, with north/south diversions of surface water since the 1950s contributing to ∼7× higher recharge. However, these diversions are regulated because of impacts on endangered species. A newly developed Central Valley Hydrologic Model shows that groundwater depletion since the 1960s, totaling 80 km3, occurs mostly in the south (Tulare Basin) and primarily during droughts. Increasing water storage through artificial recharge of excess surface water in aquifers by up to 3 km3 shows promise for coping with droughts and improving sustainability of groundwater resources in the Central Valley.

A field study was conducted from 2020 to 2023 at Kansas State University Agricultural Research Center near Hays, KS, to understand the emergence dynamics and periodicity of glyphosate-resistant (GR) Palmer amaranth (Amaranthus palmeri S. Watson) as influenced by cover crop (CC) residue and residual herbicide in grain sorghum [Sorghum bicolor (L.) Moench]. The study site was under a wheat (Triticum aestivum L.)–sorghum–fallow rotation with a natural seedbank of GR A. palmeri. Treatments included (1) fall-planted CC mixture [winter triticale (×Triticosecale Wittm. ex A. Camus [Secale × Triticum])/winter peas (Pisum sativum L.)/ rapeseed (Brassica napus L.)/radish (Raphanus sativus L.)] after wheat harvest and terminated at triticale heading stage (next spring before sorghum planting) with glyphosate alone or (2) glyphosate plus acetochlor/atrazine, (3) chemical fallow (no CC but treated with acetochlor/ atrazine and dicamba before sorghum planting), and (4) nontreated control (no CC and no herbicide). Results indicated that CC terminated with glyphosate plus acetochlor/atrazine had a delayed and reduced cumulative emergence of GR A. palmeri as compared with chemical fallow and CC terminated with glyphosate alone across all 3 yr. Compared with chemical fallow, the CC terminated with glyphosate alone and glyphosate plus acetochlor/atrazine required 66 to 643 and 105 to 1,257 more cumulative growing degree days, respectively, to achieve 90% cumulative emergence of GR A. palmeri across all 3 yr. The combined effect of CC residue with glyphosate plus acetochlor/atrazine reduced the total emergence counts of GR A. palmeri by 42% to 56% and 82% to 94% as compared with chemical fallow and nontreated control, respectively. These results suggest that fall-planted CC combined with a residual herbicide at termination can be utilized for GR A. palmeri suppression in grain sorghum.

Two separate field experiments were conducted during the 2021 to 2022 and 2022 to 2023 growing seasons at Kansas State University Agricultural Research Center near Hays, KS, to understand the emergence dynamics of glyphosate-resistant (GR) kochia [Bassia scoparia (L.) A. J. Scott] as influenced by fall- and spring-planted cover crops (CC) and residual herbicide. Study sites were under winter wheat (Triticum aestivum L.)–sorghum [Sorghum bicolor (L.) Moench]–fallow rotation with a natural seedbank of GR B. scoparia. In Experiment 1, fall-planted CC mixture (triticale/winter peas/radish/canola) was planted after wheat harvest and terminated at triticale [×Triticosecale Wittm. ex A. Camus [Secale × Triticum] heading stage (next spring before sorghum planting). In Experiment 2, spring-planted CC mixture (oats/barley/spring peas) was planted in sorghum stubbles and terminated at oats (Avena sativa L.) heading stage. Four treatments were established in each experiment: (1) nontreated control (no CC and no herbicide), (2) chemical fallow (no CC but glyphosate + acetochlor/atrazine or flumioxazin/pyroxasulfone + dicamba were used to control weeds), (3) CC terminated with glyphosate, and (4) CC terminated with glyphosate plus residual herbicide (acetochlor/atrazine for fall-planted CC and flumioxazin/pyroxasulfone for spring-planted CC). Results indicated that fall-planted CC delayed GR B. scoparia emergence by 3 to 5 wk, whereas spring-planted CC delayed emergence by 0 to 2 wk compared with nontreated control. Fall-planted CC terminated with glyphosate plus acetochlor/atrazine reduced the cumulative emergence of GR B. scoparia by 90% to 95% compared with nontreated control across both years. Similarly, spring-planted CC terminated with glyphosate plus flumioxazin/pyroxasulfone reduced the cumulative emergence of GR B. scoparia by 83% to 90% compared with nontreated control. These results suggest that fall- or spring-planted CC in combination with residual herbicide at termination can be utilized for GR B. scoparia suppression. Results from this study will help in developing prediction models for GR B. scoparia emergence under different CC strategies.

Woody plant encroachment has profound impacts on the sustainable management of water resources in water-limited ecosystems. However, our understanding of the effects of this global phenomenon on groundwater recharge at local and regional scales is limited. Here, we reviewed studies related to (i) recharge estimation methods; (ii) mechanisms by which woody plants impact groundwater recharge; (iii) impacts of woody plant on recharge across different soil and geology; (iv) hydrological repercussions of woody plant removal; and (v) research gaps and needs for groundwater studies. We identified six different methods: water balance, water table, isotopes, chloride mass balance, electrical geophysical imaging, and modeling were used to study the impact of woody encroachment on groundwater. Woody plant encroachment could alter soil infiltration rates, soil water storage, transpiration, interception, and subsurface pathways to affect groundwater recharge. The impact is highly variable, with the extent and the magnitude varying across the soil, substrate, plant cover, and topographic locations. Our review revealed mixed effects of woody plant removal on groundwater recharge. Studies of litter interception, root water uptake, soil moisture dynamics, and deep percolation along with the progression of woody plant encroachment are still limited, warranting further experimental studies focusing on groundwater recharge. Overall, information about woody plant encroachment impacts on groundwater resources across a range of scales is essential for long-range planning of water resources.

Weed management is a major challenge in pearl millet production. Limited herbicide options available for use with pearl millet further complicates weed control. To fill this knowledge gap, field experiments were conducted during the 2023 and 2024 growing seasons in Hays, Kansas, to investigate eight preemergence herbicides (labeled for use in sorghum production) for crop safety and weed control when applied to three pearl millet hybrids. Averaged across two growing seasons, S -metolachlor applied preemergence alone or in combination with atrazine, mesotrione, or atrazine + mesotrione resulted in >95% injury to all three pearl millet hybrids at 28 d after application (DAA). Visible injury with acetochlor + atrazine applied preemergence ranged from 50% to 96% among hybrids at 28 DAA. Atrazine or mesotrione applied alone or in combination were safe (<5% injury) on all hybrids. All tested preemergence herbicides provided effective (≥90%) control of Palmer amaranth at 28 DAA, except S -metolachlor, which provided 86% control. The greatest green foxtail control (≥99%) was achieved with mesotrione and acetochlor in combination with atrazine applied preemergence. All three hybrids recorded the highest grain yields (4,370 to 5,870 kg ha −1 ) with atrazine and mesotrione applied separately, and when they were combined. These results suggested that atrazine, mesotrione, or a mixture of atrazine + mesotrione applied preemergence may be safely used for Palmer amaranth and green foxtail control with newly developed pearl millet hybrids.

Playa wetlands on the west-central Great Plains of North America are vulnerable to sediment infilling from upland agriculture, putting at risk several important ecosystem services as well as essential habitats and food resources of diverse wetland-dependent biota. Climate predictions for this semi-arid area indicate reduced precipitation which may alter rates of erosion, runoff, and sedimentation of playas. We forecasted erosion rates, sediment depths, and resultant playa wetland depths across the west-central Great Plains and examined the relative roles of land use context and projected changes in precipitation in the sedimentation process. We estimated erosion with the Revised Universal Soil Loss Equation (RUSLE) using historic values and downscaled precipitation predictions from three general circulation models and three emissions scenarios. We calibrated RUSLE results using field sediment measurements. RUSLE is appealing for regional scale modeling because it uses climate forecasts with monthly resolution and other widely available values including soil texture, slope and land use. Sediment accumulation rates will continue near historic levels through 2070 and will be sufficient to cause most playas (if not already filled) to fill with sediment within the next 100 years in the absence of mitigation. Land use surrounding the playa, whether grassland or tilled cropland, is more influential in sediment accumulation than climate-driven precipitation change.

We present a checklist of 47 ant species (Hymenoptera: Formicidae) from the Wichita Mountains Wildlife Refuge in Oklahoma, USA. Surveys conducted in 2015 recaptured 67% of all historically collected species and add 12 new county records including the new state records of Pheidole tetra and Solenopsis aurea. We demonstrate the importance of sampling multiple habitats for species inventories as forests and grasslands contained compositionally unique ant assemblages. We also report an absence of the invasive red imported fire ant, Solenopsis invicta, at all sampling locations despite its occupation of the surrounding area and the southern half of the state. Combined, these results highlight the importance of protected land in conserving regional fauna and add to our understanding of the biodiversity in Oklahoma.

The authors illustrate a statistical point process model that uses the spatial occurrence of nonviolent tornadoes to predict the distribution of the rare, violent tornadoes that occur during springtime across the US central Great Plains. The average rate of nonviolent tornadoes is 55 per 10 4  km 2 per 62 years which compares with an average rate of only 1.5 violent tornadoes per 10 4  km 2 over the same period (less than 3 %). Violent tornado report density peaks at 2.6 per 10 4  km 2 (62 yr) in the city but is only 0.7 per 10 4  km 2 in the countryside. The risk of a violent tornado is higher by a factor of 1.5, on average, in the vicinity of less violent tornadoes after accounting for the population bias. The model for the occurrence rate of violent tornadoes indicates that rates are lower by 10.3 (3.6, 16.5) % (95 % CI) for every 1 km increase in distance from the nearest nonviolent tornado, controlling for distance from the nearest city. Model significance and the distance-from-nearest nonviolent tornado parameter are not sensitive to population threshold or the definition of a violent tornado. The authors show that the model is useful for generating a catalogue of touchdown points that can be used as a component to a tornado catastrophe model.

The Ogallala Formation of Miocene/Pliocene age is present over a large area of the Great Plains in the central US. The formation is composed of mostly clastic material eroded and transported eastward from the Rocky Mountains by eastward flowing rivers and streams. It contains the life-giving water that supports the population and farming activities of this vast area. However, this precious water resource is fast being depleted. The geology and geologic history, groundwater recharge, irrigation development, and water law and management of the region are outlined so as to highlight the nature and extent of the water problems facing that region and point to a more sustainable path. Further strengthening local water management and coordination with state government as well as better interstate coordination of the High Plains states will help sustain this critical water resource for generations to come.

Temporal estimates of surface soil dry aggregate-size distributions (DASD) are needed to evaluate soil management systems and estimate wind erosion. This study was conducted to determine the most accurate and precise DASD to estimate aggregate-mean diameter and amount of wind-erodible soil. Over 5400 surface samples of soil dry aggregates were collected at various times throughout the year for 2 to 4 yr at 24 locations in six states. The soils represented a wide range of management systems and intrinsic soil properties, including mineral and organic soils. We evaluated four DASDs: the log-normal determined by two methods, fractal and Weibull distributions, and compared estimates of the aggregate-mean diameter and amount of wind-erodible soil derived from the distributions. We evaluated lognormal distributions expressed as amount oversize (LNO) and undersize (LNU) and tested the effect of using different smallest and largest sieve openings sizes. The Weibull distribution is the most accurate because the ranges of error of the Weibull were generally smaller than all other distributions over the full range of sieve sizes tested, rarely exceeding 0.15. The Weibull distribution is the most precise because only the Weibull had an error mode of +/-0.05 in all sieve-- size classes tested. Using substantially different sizes for the smallest sieve-size openings had a great effect on estimates of aggregate-mean diameter and wind-erodible soil, but only when using LNO. Using substantially different sizes for the largest sieve size openings had a great effect on estimates of aggregate-mean diameter but little effect on estimates of wind-erodible soil.