Crop, Forage and Turfgrass Management最新文献

The ability of Poa annua L. to adapt to most turfgrass environments extends to its ability to develop resistance to commonly used herbicides. Herbicide resistant P. annua is of almost epidemic proportions. The loss of once viable chemical-based treatments pushes practitioners towards more expensive, and often less effective, control strategies. This management guide focuses on integrated weed management (IWM) practices for P. annua control and herbicide resistance—what it is and how to overcome it. Also discussed are resistance mechanisms and documentation of common occurrences of field-level resistance within much of the United States. Finally, a summary of some of the social and economic constraints that practitioners face in the implementation of IWM strategies for P. annua is discussed.

Plant growth regulators (PGRs) are commonly used to manage turfgrass growth on golf courses. Growing degree day (GDD) models predict the need for reapplication of PGRs, such as trinexapac-ethyl (TE) resulting in a potential loss of regulation. Optimal GDD models for application of prohexadione calcium (PC), a late-stage gibberellin inhibitor, on fairway-height turfgrasses are currently unknown. The effect of PC and TE on plant growth and stand health were evaluated in two separate seasons on mixed stands of creeping bentgrass (Agrostis stolonifera L.) and annual bluegrass (Poa annua L.) maintained at 9-mm height at the Guelph Turfgrass Institute. Five treatments (control, PC 2.8 g 100 m⁻² [0.09 oz 1000 ft⁻²], PC 5.6 g 100 m⁻² [0.18 oz 1000 ft⁻²], PC 8.4 g 100 m⁻² [0.27 oz 1000 ft⁻²], and TE 8.0 mL 100 m⁻² [0.26 fl oz 1000 ft⁻²]) were applied based on a label rate GDD schedule. Plant clipping dry weight (DW), visual color ratings and normalized difference vegetative index (NDVI) were assessed. Most PC and TE treatments effectively reduced DW and had a positive effect on visual color and NDVI. A relationship was observed between PC application rates, suggesting that higher application rates allow for greater regulation of plant growth. Rebound effects or periods of excess growth, occurred when reapplication intervals exceeded 350 GDD and had an average of thermal time greater than 21.0 GDD over a 10-day period. Using optimal GDD models for PC will assist in the effective regulation of turfgrass growth and improved stand health.

Harvest aid application can expedite soybean (Glycine max) harvest and increase efficiency through both weed and crop desiccation and has become a common practice in Louisiana soybean production systems. Field studies in 2019–2020 evaluated the influence of harvest aid application (none, paraquat at 0.28 kg/ha, sodium chlorate at 6.72 kg/ha, or saflufenacil at 0.0498 kg/ha) on seed quality affected by delayed harvest (∼20, 30, or 44 days after optimum harvest timing, i.e., 13% seed moisture). Environment was investigated in both field (natural rainfall events) and environmentally controlled growth chambers (79 or 90°F with 30% or 100% relative humidity and exposed for 24, 48, 72, 96, or 144 h) for potential impacts of prolonged rainfall conditions on soybean seed quality at harvest. Seed quality was based on a rating scale of 1 to 10 where 1 means seed in good condition and 10 means seed in poor condition based on USDA reference images. Harvest aid application had no effect on soybean seed quality affected by delayed harvest and saturated (100% relative humidity) environment. Delaying harvest beyond approximately 20 days in the field past optimum harvest timing can result in reduced seed quality regardless of whether harvest aid application occurred (0.52–2 vs 4.18–5.91 rating). In addition, seedpod exposure to high relative humidity conditions (100%) for as little as 96 h after optimum harvest timing can result in severe seed quality issues (3.96 or greater rating) regardless of whether harvest aid was used.

The incorporation of alfalfa (Medicago sativa L.) into bermudagrass [Cynodon dactylon (L.) Pers.] forage systems in the southern United States has increased. Stockpiling this mixture may extend the grazing season into the fall and winter months with high-quality forage. The objective of this 2-year study was to evaluate agronomic and structural responses of alfalfa–bermudagrass mixtures managed under five stockpiling periods (6, 8, 10, 12, or 14 weeks) in two locations (Shorter, AL, and Tifton, GA). Across locations, stockpiling mixtures for 8 weeks or longer (2400 lb DM ac⁻¹, on average) resulted in greater (P = 0.001) herbage accumulation than 6 weeks (3185 lb DM ac⁻¹). The alfalfa proportion was similar among stockpiling periods in Shorter but greater (P = 0.043) at 10 and 14 weeks than 6, 8, and 12 weeks in Tifton. A location × year × stockpiling interaction was observed for crude protein (CP, P < 0.001) and in vitro true dry matter digestibility over 48 h (IVTDMD48, P < 0.001). Crude protein concentrations were similar among stockpiling periods in 2020 in both locations. In 2019, however, CP concentrations reduced with increasing stockpiling period length in Shorter and were similar among treatments in Tifton, except for the lesser CP at 8 than at 10, 12, and 14, weeks. Forage IVTDMD48 concentrations declined with increasing stockpiling period length at both locations, with a more pronounced decline in Shorter in 2019. Results suggest that stockpiling alfalfa–bermudagrass mixtures for up to 8 weeks is a viable option to supply high nutritive value forage and lower lodging losses into the early winter months.

Turfgrass systems (e.g., home lawns, commercial properties, golf courses, athletic fields, roadsides, sod farms, parks, and other green spaces) in the US employ 820,000 individuals, have a $60 billion economic impact, and cover nearly 2% (∼63,250 mi²; 163,800 km²) of the US. Turfgrass systems provide ecosystem services such as carbon sequestration, oxygen production, water and air purification, improved soil health, pollinator habitat, and evaporative cooling. Associated disservices with turfgrass systems include nutrient and pesticide leaching, greenhouse gas and particulate matter emissions, low plant diversity, and site-specific, high water consumption. The goal of recent research efforts is to maximize the services and minimize the disservices by focusing on sustainability initiatives to develop best management practices such reducing management inputs (e.g., mowing, irrigation, fertilizer, and pesticides), incorporating pollinator-friendly spaces, adopting new technologies, quantitatively assessing ecosystem services provided, minimizing energy inputs and greenhouse gas emissions, and increasing carbon sequestration. This part-review, part-management guide summarizes these efforts, identifies knowledge gaps, and outlines how turfgrass systems can adapt to and mitigate climate change.

There is limited adoption of irrigation scheduling tools that could improve application timing and water use efficiency in row-crop production systems common to the mid-southern United States. The objectives of this manuscript are to describe a sensor-based irrigation scheduling method and review its effects on water applied and crop productivity. The effects of scheduling irrigation based on the recommended construction, deployment, and utilization of the WATERMARK 200SS granular matrix (WATERMARK) sensor on water applied, crop productivity, and crop water use efficiency were reviewed for corn (Zea mays L.), soybean [Glycine max L. (Merr.)], peanut (Arachis hypogaea L.), and cotton (Gossypium hirsutum L.) produced in the Prairie region of Arkansas and the Delta regions of Arkansas and Mississippi. For corn and soybean, on-farm research indicates the recommended irrigation threshold of −85 to −100 cbar reduces total water applied up to 40% while maintaining or improving yield up to 3%, net returns up to $39 acre⁻¹, and irrigation water use efficiency up to 51% for soil textures ranging from very fine sandy loam to clay. Similarly, for peanut and cotton, results indicate the irrigation threshold that minimizes water use while maximizing yield and net returns is −50 cbar and −100 cbar, respectively. The recommended method for scheduling irrigations with a WATERMARK 200SS soil moisture sensor promotes the efficient use of water in row-crop production systems common to the mid-southern USA.

Annual ryegrass (Lolium multiflorum; ARG) is often overseeded into bahiagrass (Paspulum notatum Fluegge) sod to provide early spring forage and extend the grazing season. Ryegrass cultivar selection for beef producers in the U.S. southeast is a major management decision, but most data available through state variety testing programs evaluate cultivar performance only from cultivated conventional seedbeds. Most producers do not consider the possible effect of ARG selection on total yield and nutritive value when overseeding into a sod compared to conventional management. Twenty ARG cultivars were planted into conventionally prepared seedbeds and overseeded into established bahiagrass plots. Forage dry matter, nutritive value, and bahiagrass suppression indexes were collected in 2019 and 2020 to determine the effects of ARG cultivar on these variables. Cultivar did not significantly affect dry matter, nutritive value, or bahiagrass suppression when overseeded. Seasonal yield of ARG decreased up to 55% in the overseeded plots and nutritive value generally decreased when compared to conventionally planted stands. Though ARG cultivars offered no apparent advantage or disadvantage to performance when overseeded, differences between planting methods were less apparent in later harvests. Considering the overseeding method involved little sod prep other than a no-till drill, it was concluded that more intense sod preparation may have led to more dynamic results among ryegrass cultivars in the fall.

The integrated crop-livestock systems of the northern High Plains are lacking in annual legumes that meet the nutrient demands of beef cattle when alfalfa (Medicago sativa) is in limited supply. We investigated the biomass accumulation, regrowth biomass, and nutritive value of sunn hemp (Crotalaria juncea) in response to initial harvest day and cutting height in irrigated and dryland studies in Wyoming. Net biomass accumulations in 105-day growing period were 4.4 tons acre⁻¹ under irrigation and 0.7 tons acre⁻¹ in dryland conditions. Initial harvest day after planting (iDAP) affected initial and regrowth biomass accumulation but did not affect net biomass accumulation in irrigated or dryland studies. Regrowth and net biomass accumulations were affected by cutting height in the irrigated study only. Nutritive value concentrations were significantly affected by iDAP in both irrigated and dryland studies. Under irrigation, net nutrient accumulation was not affected by iDAP but was significantly greater with a cutting height of 4.2 inches compared to 2.5- and 6-inch heights. In contrast, the dryland study, net nutrient accumulation was not affected by cutting height but was higher in 55–105 iDAP than 45 iDAP. In the irrigated study, a cutting height of 4.2 inches produced net accumulations higher in both biomass accumulation and nutritive value. In the dryland study a harvest time of 55–105 iDAP produced the highest net accumulation regardless of harvest time or cutting height. Sunn hemp can be harvested once or twice in a 105-day growing season to produce biomass and essential nutrients for livestock feeding.