Annual Forage Production Research Articles

Drought intensity–responsive changes in photosynthesis‐related proteins, carbohydrate pools and forage quality in Kentucky bluegrass (Poa pratensis L.)

AbstractDrought is a major factor affecting annual forage production and quality. The present study aimed to characterize drought stress–responsive changes in carbohydrate composition and forage quality–related parameters as being linked to the responses of physiological parameters during the regrowth of Kentucky bluegrass (Poa pratensis L.). Drought treatment gradually decreased leaf water potential (Ψw) to a minimum value of −2.94 MPa at day 46. Drought‐responsive increases in H2O2 concentration and lipid peroxidation were significant from day 22 (Ψw = −1.38 MPa), accompanied by the decreased chlorophyll content. Drought stress repressed Rubisco large subunit and several thylakoid membrane protein complexes (PSI, PSII dimer, PSII monomer and cytochrome b6/f). Drought also increased glucose, fructose and sucrose concentrations from day 22. A distinct increase in monosaccharides and disaccharides coincided with a reduction of fructan, especially from day 36 onward, when the enzymatic activity of fructan exohydrolases (1‐FEH and 6‐FEH) became greatly enhanced. Significant changes in forage nutritional parameters also occurred from day 36 (Ψw = −2.74 MPa), as shown by increases in neutral detergent fiber, acid detergent fiber (ADF) and ADF‐lignin with enhanced activity of polyphenol oxidase, as well as a decrease in crude protein content. These drought‐responsive changes in nutritional parameters were strongly correlated with a decrease in in vitro dry matter digestibility (IVDMD). A correlation analysis revealed that drought‐induced accumulation of H2O2 along with decreasing Ψw was closely associated with increases in fiber compounds and ADF‐lignin leading to a decrease in IVDMD. Our results indicate that drought‐responsive reductions in forage quality mainly occurred under severe drought stress (day 36 to day 46, Ψw ≤ −2.74), when H2O2 accumulation and lipid peroxidation were high, were characterized by an accompanied increase in ADF.

Comparison of dairy manure versus compost effects on short‐term nitrogen mineralization and microbial biomass in organic annual forage production system

AbstractSince the adoption of national rules for organic agriculture in the United States, there has been a continued interest in meeting crop nitrogen (N) needs using animal manure. However, a lack of consistent information on the N supplying potential of manure creates uncertainty for farmers and often leads to overapplication, which can negatively impact both crop productivity and environmental sustainability. We investigated short‐term N mineralization and microbial biomass carbon (MBC) and nitrogen (MBN) following dairy manure (DM) and its compost (DMC) application to organic annual forage production system. N mineralization was determined based on the change in mineral N during a ≤75‐day in‐field soil core‐resin bag incubation. DM and DMC application rates were targeted to supply 123 and 56 kg potentially plant‐available nitrogen (PAN) ha−1 in the first and second year of application, respectively. Net N mineralization exhibited a range of 42–277 kg N ha−1 in Year 1 and 31–54 kg N ha−1 in Year 2 across amendment treatments and increased over the course of incubation duration in both years. The proportion of total N added that was mineralized in Year 1 was greater from DM than DMC (≤35% vs. ≤7%, respectively), suggesting the inability of DMC to supply optimal levels of N to annual forages in the first crop season. In Year 2, net N mineralization did not differ between DM and DMC, but was significantly less in the unamended control than both amendments. MBC and MBN were more influenced by seasonality and soil sampling depth than by organic amendments.

Species richness and functional diversity enhance winter annual forage productivity and nutritive value

AbstractWinter annual forages can extend grazing into the cool‐season in the US southeast, however uncertainty regarding potential tradeoffs between winter annual mixtures versus monocultures exists. We examined increasingly species‐rich and functionally diverse winter annual forage mixtures at two Florida locations to evaluate impacts of including more plant species with distinct traits (e.g., different maturities and nitrogen [N] scavenging vs. N2‐fixing capabilities) on forage accumulation (FA), nutritive value, and evenness of forage distribution across the cool‐season compared with a rye (Secale cereale L.) monoculture. Furthermore, we quantified the N2‐fixing potential of winter annual legumes to measure their contribution to soil fertility and ecosystem N cycling. We found that greater species richness enhanced total cool‐season FA at both sites, ranging from 0.92 to 4.38 Mg DM ha−1 in Gainesville and 6.48 to 9.11 Mg DM ha−1 in Marianna. In Marianna, where legumes accounted for approximately 25% or more of the biomass accumulated by winter annual forage mixtures, legume inclusion enhanced forage shoot N concentration. Furthermore, >50% of the N in legume tissues derived from the atmosphere, supplying 0.18–2 kg N ha−1 in Gainesville and 30–52 kg N ha−1 in Marianna. Altogether, our data suggest that species richness enhanced winter annual forage production and legume inclusion improved forage nutritive value although these responses were site‐specific. Thus, our multi‐site study provides information that can guide decision‐making regarding appropriate winter annual forage selections to increase cool‐season forage production in the southeastern United States.

Using seasonal climate scenarios in the ForageAhead annual forage production model for early drought impact assessment

AbstractHigh interannual variability of forage production in semiarid grasslands leads to uncertainties when livestock producers make decisions, such as buying additional feed, relocating animals, or using flexible stocking. Within‐season predictions of annual forage production (i.e., yearly production) can provide specific boundaries for producers to make these decisions with more information and possibly with higher confidence. In this study, we use a recently developed forage production model, ForageAhead, that uses environmental and seasonal climate variables to estimate the annual forage production as approximated by remotely sensed vegetation data. Because, among other variables, this model uses observed summer climate data, the model output cannot be produced early enough in the year (e.g., spring months) to inform within‐season management decisions. To address this issue, we developed summer climate scenarios (e.g., extremely warm and dry and moderately cool and wet) that serve as an input in the model in combination with observed winter and spring climate data from a particular year. The summer climate scenarios used historical summer precipitation and temperature data (1950–2018) categorized into three, five, and seven percentile categories. These percentile values were then combined to represent summer climate scenarios, which were further used as the ForageAhead model input. We tested the optimal number of percentile categories to be used as the model input to obtain accurate prediction of forage production while also minimizing the number of possible temperature and precipitation combinations, which increases with the number of percentile categories. For the 19‐year period analysis (2000–2018), we also determined the most and least common scenarios that occurred in the western United States. When using five percentile categories for summer precipitation and temperature, we were able to capture the interannual variability in the spatial extent of abnormally low and high biomass production. The ForageAhead predictions captured similar spatial patterns of forage anomalies as another similar model (Grass‐Cast). This method can be made available in a user‐friendly automated system that can be used by livestock producers and rangeland managers to inform within‐season management decisions. This method can be especially valuable for flexible stocking as it provides a range of possible annual forage production scenarios by the end of May.

Tools for Predicting Forage Growth in Rangelands and Economic Analyses—A Systematic Review

Farmers and ranchers depend on annual forage production for grassland livestock enterprises. Many regression and machine learning (ML) prediction models have been developed to understand the seasonal variability in grass and forage production, improve management practices, and adjust stocking rates. Moreover, decision support tools help farmers compare management practices and develop forecast scenarios. Although numerous individual studies on forage growth, modeling, prediction, economics, and related tools are available, these technologies have not been comprehensively reviewed. Therefore, a systematic literature review was performed to synthesize current knowledge, identify research gaps, and inform stakeholders. Input features (vegetation index [VI], climate, and soil parameters), models (regression and ML), relevant tools, and economic factors related to grass and forage production were analyzed. Among 85 peer-reviewed manuscripts selected, Moderating Resolution Imaging Spectrometer for remote sensing satellite platforms and normalized difference vegetation index (NDVI), precipitation, and soil moisture for input features were most frequently used. Among ML models, the random forest model was the most widely used for estimating grass and forage yield. Four existing tools used inputs of precipitation, evapotranspiration, and NDVI for large spatial-scale prediction and monitoring of grass and forage dynamics. Most tools available for forage economic analysis were spreadsheet-based and focused on alfalfa. Available studies mostly used coarse spatial resolution satellites and VI or climate features for larger-scale yield prediction. Therefore, further studies should evaluate the use of high-resolution satellites; VI and climate features; advanced ML models; field-specific prediction tools; and interactive, user-friendly, web-based tools and smartphone applications in this field.

Rapeseed-maize double-cropping with high biomass and high economic benefits is a soil environment-friendly forage production mode in the Yangtze River Basin

The problem of the large area of winter abandoned fields in the Yangtze River Basin (YRB) has gotten worse. Moreover, there was no suitable annual forage crop planting pattern to fulfilling the annual forage needs of livestock and poultry production in the YRB region. Utilizing the abandoned field to develop high-quality and efficient forage crop planting patterns is significant. Herein as a first-time study, two growing seasons of five different double-cropping modes field experiments were performed with ryegrass-maize (RM), hairy vetch-maize (HM), rapeseed-maize (BM), milk vetch-maize (MM), and abandoned-maize (AM) to study their effects on forage production, soil properties, latter maize performance, and economic benefits. Rapeseed-maize double-cropping mode achieved the maximum annual biomass yield (37.0 Mg ha−1) and net profit value (33563 CNY ha−1), which is the most productive among the five double-cropping modes. The soil available phosphorus content after planting rapeseed was significantly higher than other modes, which was 65.6%, 37.0%, 1.5%, and 12.2% higher than abandoned field, ryegrass, hairy vetch, and milk vetch, respectively. There was a non-significant difference in soil penetration resistance (PR) between after planting rapeseed, hairy vetch, and milk vetch at the soil depth of 5–27.5 cm; whereas, the PR was reduced by 24.7% and 34.8% after planting rapeseed compared to abandoned field and planting ryegrass, respectively. Compared to the abandoned field, planting hairy vetch and milk vetch showed highly significant effects on suppression of weeds biomass and density in maize field followed by rapeseed, while planting ryegrass significantly increased the weeds biomass and density by 61.6% and 62.3%, respectively. The principal component analysis results indicated that the PR was negatively correlated to the soil fertility and maize growth traits, while positively correlated with weeds occurrence. Besides, the root activity, and root, shoot biomass of maize were significantly positively correlated with the soil fertility after harvesting winter crops. Therefore, rapeseed-maize double-cropping may be a productive pattern to promote annual forage production and enhance the agricultural economy in the Yangtze River Basin region.

Applying the CROPGRO Perennial Forage Model for long-term estimates of Marandu palisadegrass production in livestock management scenarios in Brazil

The use of long-term forage production simulation is important to studies of strategic scenarios, yield-gap predictions and production risk analysis. However, forage models have only been tested using short period data. Therefore, this study aimed to apply the CROPGRO Perennial Forage Model (CROPGRO-PFM), a mechanistic model from Decision Support System for Agrotechnology Transfer (DSSAT) platform, to simulate long-term forage production of Marandu palisadegrass {Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster [syn. Brachiaria brizantha (Hochst. ex A. Rich.) Stapf]} in different locations of Central Brazil, under different fertilization levels. We chose nine locations distributed in Amazon, Cerrado, and Atlantic Forest Biomes to simulate Marandu palisadegrass production over 36 years (1980–2016). The simulations were carried out using prior calibrations for DSSAT’s CROPGRO-PFM and, as a reference point of growth and herbage simulation, model results were initially contrasted against an agrometeorological model, the Integrated Agrometeorological Model (IAM), to check the consistency between these two different models. Then the CROPGRO-PFM was applied to simulated scenarios represented three beef cattle livestock production systems: (1) Potential production water-not-limiting and highly fertilized, (2) rainfed with high N fertilization, and (3) rainfed with low N maintenance fertilization. In general, the long-term simulations of annual forage production and seasonality were similar for the CROPGRO-PFM and IAM models. As expected for the Central Brazil region, historical averages of monthly herbage accumulation rate of potential yield scenarios were relatively constant throughout the year, declining in the winter period for most locations due to mild temperature reduction and decline of solar radiation. In general, rainfed scenarios simulations showed a seasonal cycle following the rainfall pattern, with reduction in growth rates in the dry season. During the winter season climate is the major limiting growth factor, simulated growth rates were low and similar regardless of N fertilization. Although the CROPGRO-PFM presented consistent results for long term grazing systems, further model changes, calibration, and validations are recommended to improve the process-based model as well as the knowledge about these systems.

Monitoring Climate Impacts on Annual Forage Production across U.S. Semi-Arid Grasslands

The ecosystem performance approach, used in a previously published case study focusing on the Nebraska Sandhills, proved to minimize impacts of non-climatic factors (e.g., overgrazing, fire, pests) on the remotely-sensed signal of seasonal vegetation greenness resulting in a better attribution of its changes to climate variability. The current study validates the applicability of this approach for assessment of seasonal and interannual climate impacts on forage production in the western United States semi-arid grasslands. Using a piecewise regression tree model, we developed the Expected Ecosystem Performance (EEP), a proxy for annual forage production that reflects climatic influences while minimizing impacts of management and disturbances. The EEP model establishes relations between seasonal climate, site-specific growth potential, and long-term growth variability to capture changes in the growing season greenness measured via a time-integrated Normalized Difference Vegetation Index (NDVI) observed using a Moderate Resolution Imaging Spectroradiometer (MODIS). The resulting 19 years of EEP were converted to expected biomass (EB, kg ha−1 year−1) using a newly-developed relation with the Soil Survey Geographic Database range production data (R2 = 0.7). Results were compared to ground-observed biomass datasets collected by the U.S. Department of Agriculture and University of Nebraska-Lincoln (R2 = 0.67). This study illustrated that this approach is transferable to other semi-arid and arid grasslands and can be used for creating timely, post-season forage production assessments. When combined with seasonal climate predictions, it can provide within-season estimates of annual forage production that can serve as a basis for more informed adaptive decision making by livestock producers and land managers.

Grazing intensity drives plant diversity but does not affect forage production in a natural grassland dominated by the tussock-forming grass Andropogon lateralis Nees

Andropogon lateralis is a tall and highly plastic tussock-forming grass native from southern South America. It is a frequent component of Campos and Subtropical highland grasslands that often becomes dominant under lax grazing regimes. The aim of this work was to analyze the response of species diversity and forage production of a natural grassland dominated by A. lateralis to a wide range of grazing intensity. We hypothesized that species diversity and forage production would both peak at the intermediate canopy heights determined by grazing regimes of moderate intensity. A grazing experiment was conducted in a highland grassland with mesothermal humid climate at 922 masl (Atlantic Forest biome, Santa Catarina state, Brazil) that comprised 87 species from 20 families but had 50% of its standing biomass accounted by A. lateralis. Four pre-/post-grazing canopy heights—12/7, 20/12, 28/17, and 36/22 cm (measured on A. lateralis)—were arranged in a complete randomized block design with four replications, and intermittently stocked with beef heifers from October 2015 to October 2017. Andropogon lateralis cover decreased (from 75 to 50%), and species richness increased (15–25 species m−2) as canopy height decreased. Grazing intensity did not affect annual forage production (4.2 Mg DM ha−1). This natural grassland dominated by A. lateralis had a high capacity to adjust to grazing regimes of contrasting intensity, maintaining forage production stable over a wide range of canopy heights. However, to prevent losses in floristic diversity, such grassland should not be grazed at canopy heights higher than 28 cm.

Effect of winter cover crops on water soil storage, total forage production, and quality of silage corn

Cover crops provide a wide range of benefits to farms and the environment, but this is not reflected in current adoption rates of cover cropping. If cover crops are grown for forage they may raise more interest among farmers whether as feed or as income. The objective of this study was to evaluate if introducing annual winter cover crops will contribute to the yield and quality of annual forage production and will affect soil water content. The experiment included common vetch (Vicia sativa L.), triticale (x Triticosecale Wittm. ex A. Camus) and their mixture as winter forage cover crops, fallow with nitrogen fertilization, and control plot (fallow without fertilization). The main crop was silage corn. A 2-year study was performed at three locations in northern Serbia. The following indices were calculated: forage productivity index (FP) as a ratio between cover crop and silage corn dry matter yield, forage cover crop yield advantage index (FCCYa) as a ratio between total forage yield on cover crop or fertilization treatment and control plot, and forage cover crop protein advantage index (FCCPa) as a ratio between total protein yield on cover crop or fertilization treatment and control plot. The total forage yield in 2012/2013 was higher due to more favorable weather conditions. FP was the highest on treatment with triticale in the first year and on the mixture in the second year. FCCYa was above 1, and higher on cover crop treatments in two locations. Introducing forage cover crops in crop rotation with silage corn showed an advantage in protein yield with all cover crop species, resulting in FCCPa above 1. Forage production at a location with lower FCCYa should be more focused on yield-quality balance. In contrast, in a temperate region in some years annual winter cover crops have a potential negative impact on available soil water storage for cash crop production compared to fallow-corn systems. Results indicate that cover crops impact the annual total forage yield and soil water content, but this alternation is not a species-specific effect. In the region with recurrent drought, forage yield uncertainty may be lessened by winter cover crops which enable reduced dependence on the main forage crop production.

Understanding spatial variability of forage production in California grasslands: delineating climate, topography and soil controls

Rangelands are a key global resource, providing a broad range of ecological services and economic benefits. California’s predominantly annual rangelands cover ∼12% of the state’s land area, and the forage production is highly heterogeneous, making balancing economic (grazing), conservation (habitat) and environmental (erosion/water quality) objectives a big challenge. Herein, we examined how climate and environmental factors regulate annual grassland forage production spatially across the state and among four ecoregions using machine learning models. We estimated annual forage production at 30 m resolution over a 14 year period (2004–2017) using satellite images and data fusion techniques. Our satellite-based estimation agreed well with independent field measurements, with a R 2 of 0.83 and RMSE of 682 kg ha−1. Forage production (14 year average) showed large spatial variability (2940 ± 934 kg ha-1 yr-1; CV = 35%) across the study area. The gradient boosted regression tree with 11 feature variables explained 67% of the variability in forage production across the state. Precipitation amount, especially in November (germination) and April (rapid growth), was found as the dominant driver for spatial variation in forage production, especially in drier ecoregions and during drier years. Seasonal distribution of precipitation and minimum air temperature showed a relatively stronger control on forage production in wetter regions and during wet years. Additionally, solar energy became more important in wetter ecoregions. Drought reduced forage production from the long-term mean, i.e. a 33% ± 19% decrease in production (2397 ± 926 kg ha-1yr-1; CV = 38%) resulting from a 29% ± 5% decrease in precipitation. The machine learning based spatial analysis using ‘big data’ provided insights on impacts of climate and environmental factors on forage production variation at various scales. This study demonstrates a cost-effective approach for rapid mapping and assessment of annual forage production with the potential for near real-time application.

Transitioning from conventional continuous grazing to planned rest-rotation grazing: A beef cattle case study from central Texas

Debate on the superiority of rotational or continuous grazing continues, but proponents of each call for additional research to enhance grazing management decisions. The short-term impact of transitioning from continuous grazing to an alternative grazing system is not well understood even though the transition can require substantial changes in infrastructure and management decisions related to forage availability, grazing duration and livestock movement, forage planting, and supplemental feeding. The objective of this five-year case study in a humid, subtropical environment was to evaluate real-world challenges and opportunities for beef cattle operations transitioning from conventional continuous grazing to a planned rest-rotation grazing system. The experimental data and observations (i.e., forage production, diet quality, cattle response, economics, and soil health) showcased that management changes under the planned rest-rotation system had potential for increased annual forage production, improved soil health (on cultivated grazed paddocks with multispecies forage crops, but not on grassland), and reduced costs; however, conventional continuous grazing produced higher body condition scores for cows and higher revenue. Average annual profits (~US$5.32 ac⁻¹ [US$2.15 ha⁻¹]) were similar for both grazing systems considering all economic factors. Key lessons learned and challenges faced include the difficulty of no-till establishment of cool-season multispecies forage in cultivated grazed paddocks and the importance of adequate fertilization of supplemental forage crops and dietary supplementation in the cold season.

Review of the Current Forage Production, Supply, and Quality Measure Standard in South Korea

Cattle feeding in South Korea has been heavily dependent on domestically produced rice straw and imported grain. Around 42% of domestically produced rice straw is utilized for forage, and the remainder is recycled to restore soil fertility. Approximately 35% of round baleages were made with rice straw. However, higher quality hay is desired over rice straw. Due to increasing stockpiles of rice, there has been an economic burden on the government to store the surplus; therefore production of annual forage crops in rice fields has been further promoted in recent years. Hay import from the USA currently constitutes more than 80% of total imported hays. The main imported hays are alfalfa (Medicago sativa), timothy (Phleum pretense), and tall fescue (Festica arundinacea). The estimated forage required for cattle feeding was approximately 5.4 million MT in 2016. Domestically produced forage sates only 43% of that value, while low quality rice straw and imported hay covered the rest of demand by 33% and 20%, respectively. As utilization of domestically produced forage is more desirable for forage-based cattle production, long-term strategies have been necessary to promote domestic production of high quality baleage. One such strategy has been utilizing the fertile soil and abundance of fallow rice fields of western region of S. Korea to produce forage crops. Italian ryegrass (Lolium multiflorum) is the most successfully produced winter annual in the region and is approximately 56% of the total winter annual forage production. Forage sorghums (Sorghum bicolor), sorghum × sudangrass hybrids, and hybrid corn (Zea mays) produce a substantial amount of warm-season forage during summer. Produced forage has been largely stored through baleage due to heavy dew and frequent rains and has been evaluated according to S. Korea’s newly implemented baleage commodity evaluation system. The system weighs 50% of its total grading points on moisture content because of its importance in deliverable DM content and desirable baleage fermentation; this has proved to be an effective method. Although further improvement is required for the future of forage production in South Korea, the current government-led forage production in rice fields has been able to alleviate some of the country’s shortage for quality hay.

Impacts of short-term litter manipulation on rangeland production, soil carbon, and nitrogen contents

Understanding the response of plant communities to litter removal or addition plays an important role in the sustainable management of rangelands. In this study, we investigated the effect of different litter removal and addition treatments on the annual forage production and on soil carbon and nitrogen contents of four rangeland communities in arid to semiarid areas of Iran. The results showed that litter removal reduced the contents of carbon and nitrogen in soil and the annual forage production. There was an 80% drop in annual forage production of Artemisia aucheri stand when whole litter mass was removed. The litter removal increased the annual production in Saccharum bengalense stand, and the highest forage production increment was seen when 50% of litter was removed. There was no significant difference between legume and non-legume plant stands owing to variations of soil nitrogen content. Due to the allelopathic effects in Artemisia aucheri stand, litter manipulation had no effect on the annual growth of annuals. The litter quality was more correlated to soil C and N contents and to annual forage production than to litter quantity in plant stands. Plant stands in semiarid rangelands were more sensitive to litter removal than to litter addition. Generally, short-term litter manipulation for a growing season had greater impacts on shrubland communities.

Componentes estructurales del pasto Chetumal a diferentes manejos de pastoreo

El objetivo fue estudiar el efecto de las diferentes frecuencias e intensidades de pastoreo en los componentes estructurales de una pradera de Brachiaria humidicola. Las frecuencias de cortes fueron a los 21 y 28 d y las intensidades de 9-11 y 13-15 cm de altura. Las variables se analizaron en un diseño de bloques al azar con arreglo factorial 2 x 2. Se determinó acumulación del forraje, dinámica de tallos y tasa de crecimiento foliar. En la época de lluvias se concentró 67 y 64% de la producción forrajera anual, al pastorear a 21 y 28 d, respectivamente. La densidad de tallos durante la época de lluvias fue 11% mayor en el primer ciclo, 11 y 20% en nortes de ambos ciclos al pastorear cada 21 día. La tasa de aparición de tallos en la época de lluvias disminuyó 21% al ampliar el intervalo entre pastoreo de 21 a 28 días, respectivamente. La mayor acumulación del forraje, recambio de tejido foliar y peso por tallo, se obtuvo al pastorear a una intensidad ligera de 13-15 cm de altura cada 28 días

Forum: Critical Decision Dates for Drought Management in Central and Northern Great Plains Rangelands

Ranchers and other land managers of central and northern Great Plains rangelands face recurrent droughts that negatively influence economic returns and environmental resources for ranching enterprises. Accurately estimating annual forage production and initiating drought decision-making actions proactively early in the growing season are both critical to minimize financial losses and degradation to rangeland soil and plant resources. Long-term forage production data sets from Alberta, Kansas, Montana, Nebraska, North Dakota, South Dakota, and Wyoming demonstrated that precipitation in April, May, and June (or some combination of these months) robustly predict annual forage production. Growth curves from clipping experiments and ecological site descriptions (ESDs) indicate that maximum monthly forage growth rates occur 1 mo after the best spring month (April to June) precipitation prediction variable. Key for rangeland managers is that the probability of receiving sufficient precipitation after 1 July to compensate for earlier spring precipitation deficits is extremely low. The complexity of human dimensions of drought decision-making necessitates that forage prediction tools account for uncertainty in matching animal demand to forage availability, and that continued advancements in remote sensing applications address both spatial and temporal relationships in forage production to inform critical decision dates for drought management in these rangeland ecosystems.

Monitoring Drought Impact on Annual Forage Production in Semi-Arid Grasslands: A Case Study of Nebraska Sandhills

Land management practices and disturbances (e.g. overgrazing, fire) have substantial effects on grassland forage production. When using satellite remote sensing to monitor climate impacts, such as drought stress on annual forage production, minimizing land management practices and disturbance effects sends a clear climate signal to the productivity data. This study investigates the effect of this climate signal by: (1) providing spatial estimates of expected biomass under specific climate conditions, (2) determining which drought indices explain the majority of interannual variability in this biomass, and (3) developing a predictive model that estimates the annual biomass early in the growing season. To address objective 1, this study uses an established methodology to determine Expected Ecosystem Performance (EEP) in the Nebraska Sandhills, US, representing annual forage levels after accounting for non-climatic influences. Moderate Resolution Imaging Spectroradiometer (MODIS)-based Normalized Difference Vegetation Index (NDVI) data were used to approximate actual ecosystem performance. Seventeen years (2000–2016) of annual EEP was calculated using piecewise regression tree models of site potential and climate data. Expected biomass (EB), EEP converted to biomass in kg*ha−1*yr−1, was then used to examine the predictive capacity of several drought indices and the onset date of the growing season. Subsets of these indices were used to monitor and predict annual expected grassland biomass. Independent field-based biomass production data available from two Sandhills locations were used for validation of the EEP model. The EB was related to field-based biomass production (R2 = 0.66 and 0.57) and regional rangeland productivity statistics of the Soil Survey Geographic Database (SSURGO) dataset. The Evaporative Stress Index (ESI), the 3- and 6-month Standardized Precipitation Index (SPI), and the U.S. Drought Monitor (USDM), which represented moisture conditions during May, June and July, explained the majority of the interannual biomass variability in this grassland system (three-month ESI explained roughly 72% of the interannual biomass variability). A new model was developed to use drought indices from early in the growing season to predict the total EB for the whole growing season. This unique approach considers only climate-related drought signal on productivity. The capability to estimate annual EB by the end of May will potentially enable land managers to make informed decisions about stocking rates, hay purchase needs, and other management issues early in the season, minimizing their potential drought losses.

Phosphorus Improves Leaf Nutrient Concentrations in Wheat, Oat, and Cereal Rye

Core Ideas Increased P availability increases leaf P and Mg in wheat, oat, and rye. The grass tetany ratio is improved with greater P availability in these species. Unlike cereal rye and oat, wheat increases shoot growth with high P levels. Winter annual species grown for forage are prone to mineral imbalances that could result in animal nutritional disorders, such as grass tetany. Adequate soil P has been found to be critical for the growth and adequate nutrient content of Mg, Ca, and K in other forages for grazing animals. This study examined the effect of P availability on growth and leaf nutrients in annual cereal grains commonly grown for winter forage. Winter wheat (Triticum aestivum L.), oat (Avena sativa L.), and cereal rye (Secale cereal L.) were grown hydroponically in greenhouse conditions in complete nutrient solutions with P treatments of 0, 200, 400, and 800 µmol L−1 P. After 32 d, plants were harvested and analyzed for P, Mg, Ca, and K content. Shoot growth of all three species increased from 0 to 200 µmol L−1 P; however, only wheat shoots increased incrementally with the other P treatment concentrations. Leaf P also responded incrementally to increased P treatments in all three species. Wheat and cereal rye exhibited increases in leaf Mg and improved grass tetany ratio from 200 to 400 µmol L−1 P, whereas oat showed these improvements from 0 to 200 µmol L−1 P treatments. This study suggests increased P availability could improve the grass tetany ratio, with or without increased shoot growth, in winter annual forage production on low P soils.

Floristic enrichment of the understory increases forage production and carrying capacity of temperate silvopastoral systems

In silvopastoral systems, the use of land for multiple purposes diversifies economic income and improves the stability of the system. If shading levels are medium or high, cattle production is often limited by the absence of one or more forage components of the herbaceous layer (such as perennial grasses). In the present study, we hypothesized that perennial C3 cover is a major determinant of cattle production because pasture cover throughout the year is higher and more persistent than that of annuals C3 and thus forage productivity is more stable over time. Therefore, we studied the introduction of orchardgrass into a silvopastoral system of the Parana River Delta (Argentina) and estimated forage production and carrying capacity of the enriched grassland. Between March 2013 and December 2014, we measured forage production and cover in four paired stands either sown (S) or not sown (NS) with C3 grasses by successive harvests of the herbaceous component. The contribution of the different plant functional types to annual forage production was separated across seasons and livestock potential was estimated through carrying capacity. S stands had 105% higher annual forage production than NS stands (S: 2.546 vs. NS: 1.240 kg ha−1 y−1, p = 0.037), with forage species (C3, C4, orchardgrass, Fabaceae) contributing 98.8% to total biomass. The greatest forage production gap between S and NS stands was in winter (S: 594 vs. NS: 23 kg ha−1 90 day−1), when carrying capacity increased ten times in S stands. This is the first research in the area that describes grassland composition and forage production in the understory of plantations, with substantial improvements in livestock carrying capacity of silvopastoral systems.

Improved water management of a poorly drained floodplain soil and the impact on forage production and nitrate concentration

As livestock demand and production continue to rise in the United States, there is a greater need for increased forage production and improved forage quality. Forage production will need to expand to soils with production restrictions, such as poorly drained floodplain soils, in order to meet future demands. The objectives of the study were to evaluate the impact of free drainage (FD), managed drainage systems (MD), and no drainage (ND) on forage production, nitrogen (N) uptake, and nitrate (NO3) concentration in rye (Secale cereale L.) and forage sorghum (Sorghum bicolor [L.] Moench). On average across years, MD did not increase forage production compared to FD, but the presence of subsurface drainage (both FD and MD) increased total forage biomass production by 27% to 32% compared to ND. Annual plant N uptake increased 30% with MD and 41% with FD compared to ND when averaged across the four-year study. Nitrate concentration in rye mass never reached a concentration that could impact cattle grazing the forage over the four-year study. Regardless of subsurface drainage system, NO3 concentration in forage sorghum in two study years ranged from 1,310 to 4,520 mg kg−1, which corresponded to toxic to extremely toxic levels. Dry summer months may have contributed to the high NO3 concentrations observed in forage sorghum. Subsurface drainage may provide farmers with an opportunity to increase annual forage production from rye and forage sorghum, but farmers should have forage sorghum tested for NO3 concentrations before feeding.