Nutrient Cycling and Crop Responses on Integrated Crop-Livestock Systems

Integrated crop-livestock systems (ICLS) can bring numerous benefits to crops or livestock systems, such as increase soil C sequestration, farm profitability, and provisioning of ecosystem services. In a changing world, production systems need to become more resilient and sustainable. Specialized agriculture is characterized by a high level of inputs and outputs, and oftentimes specialize in a single crop to simplify management. However, such operational systems stray away from sustainable standards. Furthermore, specialized cropping systems may face problems such as persistence of pests and diseases, loss of biodiversity, stagnant yields, development of herbicide-resistant weeds, soil erosion and consequently loss of soil organic matter. Recombining crops and livestock in a broad and complementary system is to look back into the past to adopt a practice that used to be common centuries ago. With the advancement of technology and better understanding of this management practice, ICLS appear as an option to provide ecosystem services from agricultural lands, while potentially increasing crop production. Such systems have shown benefits as increasing in soil organic matter, increase in biodiversity, and nutrient cycling. There is an array of ICLS, which may include short and long grazing cycles, more than one animal category, crops from many different functional groups, and trees. Here, we will discuss some of the aspects in nutrient cycling and crop responses on ICLS, giving examples to call attention to some of the advantages ICLS can provide

Herbage and Livestock Responses for N-Fertilized and Grass-Legume Grazing Systems

Forage legumes provide an alternative N source in grazing systems. The objective was to evaluate plant and animal responses in N-fertilized or grass-legume-based systems under continuous stocking during winter and summer, from 2016-2019. The three treatments consisted of year-round forage systems including winter and summer forage components. The first system (Grass+N) included N-fertilized (112 kg N ha-1 yr-1) ‘Argentine’ bahiagrass (Paspalum notatum) pastures during the summer, overseeded with a mixture (56 kg ha-1 of each) of ‘FL 401’ cereal rye (Secale cereale) and ‘RAM’ oat (Avena sativa) during winter with a second application of 112 kg N ha-1 yr-1. Total annual fertilization for this treatment was 224 kg N ha-1 yr-1. System 2 (Grass + clover) included unfertilized Argentine bahiagrass during summer, overseeded with a similar rye-oat mixture, plus a mixture of clovers [17 kg ha-1 of ‘Dixie’ crimson (Trifolium incarnatum), 6.7 kg ha-1 of ‘Southern Belle’ red clover (Trifolium pratense), and 3.4 kg ha-1 ball clover (Trifolium nigrescens), fertilized with 34 kg N ha-1 during winter. System 3 (Grass+CL+RP) included the germplasm Ecoturf rhizoma peanut (Arachis glabrata; RP) and Argentine bahiagrass during the summer, overseeded with the same a similar rye-oat-clover mixture used in System 2 and fertilized with 34 kg N ha-1 during winter. Pastures were continuously stocked using variable stocking rates. Results indicate that clover inclusion during winter improved herbage distribution along the grazing season. Integrating RP during summer increased steer ADG by nearly 80% compared with Grass+N or Grass+Clover (bahiagrass monocultures during summer). While N fertilizer allowed for greater stocking rates, it did not improve animal performance throughout the year. Overall, similar gain per area was achieved in Grass+CL+RP than Grass+N, with lesser N-fertilizer inputs

Breeding Small Grains as a Forage, Silage and Cover Crop for the Southern Coastal Plain (USA) in a Changing Climatic Environment

Forage breeding of small grains in the southern Coastal Plains region of the U.S. mimic many other countries experiencing climate changes and breeding strategies should be similar for improving small grains grown for forage, silage or as cover crops. Significant focus on improvements in stress-adaptation has encouraged members of the SunGrains cooperative to cross, evaluate and develop experimental lines with inherent adaptation to climatic conditions including heat stress, drought tolerance, short-day and long-day forage production periods, and flooded conditions for events with storm-related, short-term durations. Many new cultivars, grown throughout the southeastern U.S. have resulted from breeding selection under abiotic and biotic stresses, adapted to climate change and related concerns, such as disease and insect pests

Legumes as a Strategy for Reducing Greenhouse Gas Emissions of Forage-Livestock Systems

Incorporation of legumes into forage systems has been a widely adopted strategy to increase pasture productivity and forage nutritive value, while reducing N inputs. Considering the population growth, and the diminishing land resources for food production, the need to increase the food supply will have to be balanced with the environmental impact of these systems, particularly their carbon footprint. Enteric methane production represents the largest source of greenhouse gas emissions from livestock. Certain forage legumes have evolved plant secondary compounds, such as tannins and other polyphenols, which have been associated with reductions in enteric methane emissions. Studies were conducted at Utah State University (USU), and at the University of Florida, North Florida Research and Education Center (UF-NFREC) to assess in vivo methane emissions in grazing cattle, using the SF6 tracer technique. At USU, cattle grazing pastures of Birdsfoot trefoil (Lotus corniculatus; BFT) emitted less methane per unit of dry matter consumed when compared with cattle fed a totally mixed ration (50% barley grain, 25% alfalfa hay, and 25% corn silage) in ad libitum amounts. However, emissions in cattle grazing BFT did not differ from those grazing the legume Cicer milkvetch (Astragalus cicer), or a traditional pasture-finishing system based on Meadow brome (Bromus riparius). At UF-NFREC, three livestock-forage systems were tested during three consecutive years to determine the effects of including the legume Rhizoma peanut (Arachis glabrata Benth.; BHR) in bahiagrass pastures (Paspalum notatum Flügge) fertilized (BH) or not (BHF) with N during the warm season. No differences were observed in methane emissions (g d-1), or in methane emission intensity. From the legumes grazed in these experiments, only BFT contains significant concentrations of tannins. Thus, the potential to mitigate livestock enteric methane emissions by grazing legumes appears to be directly related to the presence of tannins

Sustainable Intensification of Livestock Systems Using Forage Legumes in the Anthropocene

Sustainable intensification of livestock systems implies greater efficiency in resource utilization resulting in greater output of products and other ecosystem services per unit of resource input. Strategies to improve resource use efficiency include diversification of plant and ruminant species with complementary resource use. Forages that have root systems with contrasting architecture and exploring different soil layers with complementary use of resource acquisition (e.g., nutrients, water) could enhance primary productivity. Belowground interactions with soil microbiota (e.g., mycorrhizae) is key to enhance resource utilization. Forages with complementary canopy characteristics that helps enhancing light interception and utilization could also lead to greater resource utilization. Integrating forage legumes into livestock systems is a viable way to reduce input of industrial N fertilizer, reducing the use of fossil fuels and helping to mitigate global warming, a major problem during the Anthropocene. Some forage legumes have greater concentration of secondary compounds such as condensed tannins that might reduce emission of greenhouse gases (GHG) from eructation and from excreta. Livestock are major contributors to overall GHG emissions from agricultural systems, and any reduction on those emissions without compromising animal performance is welcome. Furthermore, forage legumes might enhance cattle performance because of greater nutritive value, resulting in greater beef production per unit of GHG released. In fact, shortening the production cycle and improving cattle reproductive efficiency could have major impact reducing the overall carbon footprint of the system. Grazing systems with more diversified plant species are typically more resistant and resilient, adapting to current climate changes during the Anthropocene. There are examples of successful integration of forage legumes into livestock systems in different regions of the world, with major reduction in off-farm inputs and maintaining the system productive. These successful examples must be used to increase adoption and to improve the efficiency of current livestock systems

Ecosystem Services Provided by Overseeding Aeschynomene Into Bahiagrass Pastures in South Florida

Aeschynomene (Aeschynomene americana L.) is a warm-season annual legume commonly overseeded into warm-season perennial grass pastures in tropical and subtropical regions. Although aeschynomene usually increases forage production and nutritive value, there is limited information about the ecosystem services provided by this legume. The objective of these studies was to evaluate the effects of overseeding aeschynomene into bahiagrass (Paspalum notatum Flüggé) pastures on nutrient dynamics and microbial N-cycling gene abundances. The studies were conducted in Ona, FL, from April to March 2019-2020 and 2020-2021. Treatments were the split-plot arrangement of two forage systems treatments (overseeding aeschynomene into bahiagrass or bahiagrass monoculture; main plots) and two N fertilization levels [0 (control) and 60 kg N ha-1 ; sub-plot], distributed in a randomized complete block design with four replicates. Forage characteristics were evaluated 8-wk after seeding and every 35 d thereafter. The static chamber technique was used to estimate nitrous oxide (N2O) emissions. The litter bag technique was used to estimate organic matter (OM) and N decomposition. Nitrogen-cycling gene abundances were measured by qPCR. Bahiagrass-aeschynomene had greater crude protein concentration than bahiagrass monoculture but there was no difference in forage accumulation. Nitrogen fertilization increased forage accumulation and daily N2O emissions. Litter from bahiagrass-aeschynomene had greater OM and N decomposition rates than bahiagrass only, and N fertilization did not affect litter decomposition. There were no differences in N-cycling microbial gene abundances among treatments. Overseeding aeschynomene into bahiagrass may provide additional ecosystem services, but the magnitude is conditional to the establishment and proportion of aeschynomene in the pasture botanical composition

Contribution from Tree Legumes to Mixed Grass-Legume Pastures

Legumes and associated microorganisms may fix N from atmosphere and benefit grass on mixed grass-legume pastures. Nitrogen may be transferred by different mechanisms, including direct transfer of N compounds by roots, decomposition of nodules, roots, litter from legume (Nair 1993), and through animal excreta after legume intake by cattle. Silvopastoral systems including tree legumes may become a viable option in tropical regions, considering the increasing prices of N fertilizers compared to farm products such as beef and milk. This experiment evaluated legume contribution on mixed grass-legume pastures in the coastal region of Pernambuco State, Brazil

Nutrient Return from Plant Litter and Cattle Excretion Grazing on N-Fertilized Grass or Grass-Legume Pastures in North Florida

Nutrient recycling via plant litter and livestock excreta is an important ecosystem service provided by grasslands. This study determined nutrient return via these pathways in three grazing systems. The experiment was conducted from May to October (2016 and 2017) and treatments were: 1) Nitrogen fertilized bahiagrass (Paspalum notatum Flügge) pastures (112 kg N ha-1) during the warm-season, overseeded with a mixture (56 kg ha-1 of each) of ‘FL 401’ cereal rye (Secale cereale, L.) and ‘RAM’ oat (Avena sativa, L.) during the cool-season (BGN); 2) Ecoturf Rhizoma peanut (Arachis glabrata Benth.)/bahiagrass pastures during the warm-season, overseeded with similar rye/oat mixture fertilized with 34 kg N ha-1 plus a mixture of clovers (Trifolium incarnatum L., T. pretense L., and T. nigrescens L.) during the cool-season (BGRP); 3) unfertilized bahiagrass pastures during the warm-season, overseeded with similar rye/oat grass/clover mixture + 34 kg N ha-1 during the cool-season (BG). Litter mass was evaluated every 5wk. Litter decomposition was evaluated with incubation periods of 0, 2, 4, 8, 16, 32, 64, 128, and 256 days. Urine and fecal samples were collected for N concentration analysis. There was a net return of 47 kg N ha-1 season-1 via litter in all three systems without differing among them. In addition, litter decomposition rates were not different in the three systems. Conversely, N returned via excreta (urine and feces) was greater (63, 27, and 51 kg N ha-1 season-1) than that returned via litter (58.6, 41.6, and 41.2 kg ha-1 season-1). When assessing the proportions of N returning to the system via litter or excreta, no differences were observed among treatments, and on average 65.1 % of the N returned via excreta vs. 34.9 % returning via litter. The introduction of legumes could reduce the inputs from N fertilizers in grazing systems and keep the productivity similar because of more efficient N cycling

Leaf Epidermal Descriptors of Forage from Caatinga, NE Brazil

In the Brazilian semi-arid region, the predominant vegetation is the Caatinga, which has a diversity of plant species, some endemic and presenting forage potential. The characterization of the plant anatomy is important for animal diet studies, using a microhistological technique (Scott and Dahl 1980) for estimating the diet botanical composition from ruminant faeces. This paper determined leaf epidermal descriptors for Caatinga species using microscopic slides

Animal Performance in Signalgrass Monoculture or in Silvopastoral Systems

Silvopastoral systems (SPS) can increase overall productivity and long-term income due to the simultaneous production of trees, forage, and livestock. This 2-yr study evaluated animal performance and herbage responses in C4-grass monoculture or in SPS in the sub-humid tropical region of Brazil. The experimental design was randomized complete block with three replications. Treatments were: Urochloa decumbens (Stapf.) R. Webster (Signalgrass) + Mimosa caesalpiniifolia Benth (SPS-Mimosa); Signalgrass + Gliricidia sepium (Jacq.) Kunth ex Walp (SPS-Gliricidia); and Signalgrass monoculture (SM). Response variables included herbage and livestock responses. Cattle were managed under continuous stocking with variable stocking rate. There was interaction between treatment × month for herbage mass. Green herbage accumulation rate ranged from 20 to 80 kg DM ha-1d-1 across months, with SPS-Mimosa presenting lower rates. Average daily gain was greater in SPS-Gliricidia, followed by SM, and SPS-Mimosa, respectively (0.77; 0.56; 0.23 kg d-1), varying across months. Stocking rate ranged from 0.86 to 1.6 AU ha-1. Total gain per area during the experimental period was greater for SPS-Gliricidia (423 kg BW ha-1), followed by signalgrass in monoculture (347 kg BW ha-1), and SPS-Mimosa (50 kg BW ha-1). Silvopasture systems using signalgrass and gliricidia enhanced livestock gains compared with signalgrass in monoculture, and mimosa trees outcompeted signalgrass, reducing livestock gains. Silvopasture systems with tree legumes have potential to provide numerous ecosystem services and reduce C footprint of livestock systems in the tropics, however, the choice of tree species is key and determined by which ecosystem service is prioritized