Instituto Nacional de Investigación Agropecuaria

Ecological intensification of beef cow-calf systems on native grasslands requires quantitative tools that link herbage condition, animal physiology, and management at the whole-farm level. We present and evaluate the animal dynamics module of PAmpa Sustainable grAzing Livestock Management (PASpALuM), a farm-scale model developed for high-diversity Pampas grasslands. The module simulates individual animal herbage intake, energy balance, BW, body condition score (BCS), and reproduction as functions of herbage height, management practices, and weather. Herbage height and BCS are used as key, farmer-measurable state variables that integrate sward structure, intake regulation, metabolic status, and reproductive performance. Output is probabilistic as a result of stochasticity in animal input data and the parameters governing pregnancy. Model performance was evaluated using (i) experimental data on herbage intake and daily weight gain of heifers under contrasting herbage allowances during two single seasons (n=16), and (ii) on-farm data from six cow-calf farms to assess cow BW, BCS and pregnancy, and herbage height during one mating season. Herbage height and mass were simulated by the herbage module presented in an accompanying paper. Simulated herbage intake showed strong agreement with the experimental data, resulting in mean absolute difference (MAD) and RMSE values of 0.44 and 0.52kgDM/animal per day, respectively. MSD was dominated by 'lack of correlation' (79%), whereas 'squared bias' (13%) and 'non-unity slope' (8%) were small, indicating limited systematic error and adequate representation of intake responses across pasture conditions. Daily weight gain was well reproduced (MAD and RMSE of 0.05 and 0.06kg/animal per day, respectively). Modelling efficiency (EF) was 0.6 for herbage intake and daily weight gain, indicating good model performance. MAD and RMSE values over 90days for cow BW, BCS, and herbage height were 22.6 and 25.4kg, 0.35 and 0.40 units, and 1.3 and 1.4cm, respectively. EF was 0.6, 0.5 and 0.7, respectively. Pregnancy percentage was predicted within 95%-confidence intervals on five of six farms, with a MAD of 4.2% points. The sensitivity of actual DM intake was greatest for sward height. The model includes the option to operate it with multiple paddocks. Together with the individual-animal-based approach and the use of easily measured state variables, herbage height and BCS, PASpALuM is distinct from other native grassland production system models. We discuss its scientific merits and validity domain, and its use for scaling the ecological intensification paradigm on cow-calf farms in the Pampas region.

We hypothesize that increasing N application rates will affect N use efficiency (NUE) for lambs grazing warm‐season annual grasses. We evaluated the effect of N fertilizer application rates (50, 100, 200, and 400 kg N/ha) on forage pearl millet ( Pennisetum glaucum (L.) R.) and animal responses: N balance and NUE per animal and per area basis. The experiment was conducted in a randomized complete block design with three replicates over a 70‐day grazing period. Pastures were grazed under continuous stocking using variable stocking rate (SR) to keep pasture sward height at 30 cm across treatments. Nitrogen application rate did not affect ( p > 0.05) animal ADG (g/day) and his N balance but increased ( p < 0.01) forage production resulting in an increase in SR from 850 to 1560 kg live weight (LW)/ha. This also resulted in an increase of N excretion ( p < 0.01; 55–124 kg N/ha), particularly via urine (34 to 91 kg N/ha). Animal NUE (kg LW gain/kg of N applied) decreased with increasing N application rates. These results demonstrate that the major impacts of N application occur on pasture growth and its ability to support greater SR, which increases N deposition via excreta.

Abstract Plant litter decomposition is the process through which plant-derived organic matter is recycled in terrestrial ecosystems. One of the drivers of decomposition is photodegradation, light-induced reactions that result in litter mass loss and transformations that accelerate the decomposition process. Photodegradation has been mostly studied in arid ecosystems, but mesic grasslands with monsoonal climate have been almost absent in the literature. In these ecosystems, standing dead biomass might remain exposed to solar radiation during dry winters while the effects of photodegradation accumulate. With the start of the warm and humid seasons, biotic decomposition might increase as a consequence of the changes in litter quality caused by sunlight. We aimed to study the impact of different wavelengths of solar radiation on litter mass loss and litter quality changes in a montane grassland with a monsoonal climate. We incubated litter from two dominant grasses under filters that generated treatments of full solar radiation, reduced UV radiation and reduced UV to short-wave visible radiation. We tracked changes in physical litter traits throughout the experiment under the three light treatment levels. We found an increase in litter mass loss due to sunlight exposure for both species, but each species reacted to a different range of wavelengths. We found evidence of enhancement of biotic decomposition by solar radiation (photofacilitation) in one of the two species, through an increase in β -glucosidase enzymatic activity. Seasonality affected litter decomposition of one species only by increasing mass loss depending on whether it was placed in the field during the dry winter or the humid spring. Finally, we found evidence of changes in physical litter traits caused by solar radiation, mainly in leaf mass per area (LMA) and water adsorption capacity. Our results represent the first proof of photodegradation in a productive grassland in this region, and highlight the fact that photodegradation is not constrained only to arid environments. Additionally, this study emphasizes the importance of litter physical traits in regulating carbon cycling through plant litter decomposition in terrestrial ecosystems. Open Research Statement Data are not yet provided as the study is currently under peer review. Upon acceptance, data will be archived in Zenodo. However, full datasets can be made available to the editorial board if required for the evaluation of the manuscript.

The Río de la Plata Grasslands (RPG) experienced a substantial agricultural expansion and intensification over the last three decades, with considerable impacts on C stocks among other ecosystem services. Converting agricultural land back to grassland is thus proposed as a strategy for removing atmospheric CO2 and sequestering carbon in the form of soil organic matter. However, the temporal dynamics of C recovery during spontaneous grassland restoration is still uncertain for this region. This study aims to describe the dynamics of soil organic carbon (SOC) recovery in fields with agricultural use in the past, in one of the most transformed regions of the RPG. For this purpose, we used a spatial chronosequence approach to sample rice old-fields (the main crop in this area) with similar soil types but different times since abandonment (2–25 years), allowing us to assess temporal patterns of SOC recovery in the absence of long-term monitoring data. These empirical data were then compared with simulations from the Century model, which incorporated different agricultural histories and grazing intensities following abandonment. The time required for the stabilization of carbon stocks depends on the magnitude of SOC losses generated by previous agricultural use and the subsequent grazing management, with recovery being slower in old-fields that experienced greater carbon depletion. Both approaches revealed SOC recovery over time; however, early accumulation rates were much higher in empirical data (10.5 vs. 0.6 t C ha⁻1 yr⁻1), likely because they integrate diverse agricultural histories and grazing intensities that the Century model separates into distinct scenarios. The different Century simulations integrate the variability that is not possible to discriminate with a field based approach, allowing us to correct possible artifacts and to generate more accurate predictions of how the system responds to different agricultural and post-agricultural management. After 30 years of agricultural abandonment, accumulation rates derived from both approaches stabilize at values consistent with those expected for grassland ecosystems. This suggests that carbon accumulation could compensate for up to approximately two-thirds of the methane emissions generated by livestock grazing, highlighting the potential contribution of restored grasslands to climate change mitigation.

This article summarizes our research on integrated timber investment returns, wood stumpage costs, and forest carbon production costs in 2023 for a representative selection of 15 countries, across 44 planted and 1 natural species/management regimes, using capital budgeting criteria, at a real discount rate of 8%, without land costs. Despite a large amount of disparate research, few, if any, studies have provided integrated estimates of investments, wood fiber costs, and forest carbon costs for CO2 offsets using fundamental primary data and production economics approaches. We expanded our prior research that estimated present values and internal rates of return for timber investments, using planted forest growth and yield, input management costs, and timber products prices by selected countries and species. We extended the production economics and forest investment calculations to estimate average stumpage costs for wood fiber per cubic meter per rotation. In addition, we calculated the costs to produce forest carbon for offsets in terms of carbon dioxide equivalent. Timber investment returns by country and species were the largest in tropical Asia and smallest in the Northern Hemisphere (including the United States and Europe), and South America had calculated returns between the two regions. Based on prior research, more developed countries had less investment risk, and had land markets that were more open for foreign investments. Wood costs and forest carbon production cost outcomes by country and species differed substantially from timber investment returns. The discounted wood costs per m3 were generally cheapest if the establishment costs and management inputs were minimized, or for long rotation planted stands. Forest carbon costs had similar rankings to wood costs, and even similar numbers, but were using a different metric—dollars per tCO2e. The calculated forest carbon costs are certainly among the cheapest of all types of typical carbon offsets. They were equal to or much less than the six primary developed country compliance market prices. However, they were higher than the current depressed public voluntary market prices. These results can be used for private, government, or nongovernment investments and for public policy intervention considerations.

This study aimed to estimate the association of udder health and herd management practices with bulk tank SCC (BTSCC) and the partial costs of subclinical mastitis (milk yield losses and penalties) on dairy farms in Uruguay. As part of a cross-sectional study, a survey on udder health and herd management practices was conducted on 190 randomly selected dairy farms stratified by region and milk shipment volume (MSV). Herd data comprising 13 mo of BTSCC and MSV were obtained from the dairy processing company, and BTSCC values exceeding 250 × 103 cells/mL (BTSCC >250) were identified. Multivariable regression models were developed to evaluate the association between udder health and herd management practices and 4 response variables on a monthly basis: BTSCC, BTSCC >250, milk yield losses, and penalties. In addition, we calculated the population attributable fraction (PAF) of practices associated with BTSCC >250 and their attributable cost. Postmilking teat disinfection (78%) and dry-cow therapy (80%) showed the highest adoption rates. Some practices such as culling of chronically infected cows based on records (11%), the use of automatic cluster removers (22%), the maintenance of calving areas (24%), monthly individual SCC (ISCC; 16%), and a monthly California Mastitis Test (CMT) on all cows (10%) showed low adoption rates. When adoption rates differed across MSV levels, small farms consistently had lower uptake. The lack of use of postmilking teat disinfection was associated with a higher BTSCC (30 ± 11 × 103 cells/mL), higher odds of BTSCC >250 (odds ratio = 2.45), and higher milk yield losses ($1.22 ± $0.45 per cow per month). Similarly, farms that manually removed clusters showed higher BTSCC (29 ± 13 × 103 cells/mL), higher odds of BTSCC >250 (odds ratio = 2.73), and higher penalties ($0.67 ± $0.28 per cow per month). For monthly ISCC, the odds of BTSCC >250 and the milk yield losses and penalties were lower, whereas on farms with maintenance of calving areas, the odds for BTSCC >250 and the penalties were lower. The partial cost of subclinical mastitis was $9.2 ± $3.9 per cow per month. Yield losses comprised 88% of the cost, and variability among farms was high. Practices associated with BTSCC >250 (postmilking teat disinfection, use of automatic cluster removers, monthly ISCC, and maintenance of calving areas) showed high PAF values. Our results highlight opportunities, some with a potential population effect, to reduce subclinical mastitis and increase overall farm profitability, particularly on smaller farms, and underscore the potential benefits of improved udder health management in Uruguay.

Lotus angustissimus is a promising forage legume increasingly used to improve naturalgrasslands in Uruguay. However, a specific rhizobial inoculant for this species has not yet been developed, and the identification of its autochthonous symbionts remains unknown. Instead, L. angustissimus is inoculated with Bradyrhizobium sp. U531 the commercial inoculum for Lotus subbiflorus . We evaluated the symbiotic efficiency of sixteen Bradyrhizobium strains isolated from L. angustissimus nodules in a site without inoculation for 15 years, revealing efficient soil rhizobia suitable for inoculant development. Under controlled conditions, GL3 and GL5 strains significantly exceeded the symbiotic efficiency of strain U531 in L. angustissimus . In L. subbiflorus , strain GL5 exceeded the symbiotic efficiency of strain U531. Genomic and phylogenetic analyses showed that strain GL3 belongs to the species Bradyrhizobium canariense BTA‐1 T , whereas strain GL5 is related to Bradyrhizobium nitroreducens TSA1 T , although average nucleotide identity suggests that it represents a different species. Despite their taxonomic divergence, both strains share a high percentage of identity with the nodBC and nifHK genes of Bradyrhizobium sp. WSM471, suggesting horizontal gene transfer of the symbiotic loci. The presence of denitrification genes ( nap , nor , and nos ) and nitrate‐dependent anoxic growth in both strains was also confirmed. These findings demonstrate, for the first time, that B. canariense GL3 can efficiently nodulate L. angustissimus and L. subbiflorus . Bradyrhizobium sp. GL5, related to B. nitroreducens TSA1 T , is also reported to establish an efficient symbiosis with these legumes. Due to the high symbiotic efficiency of these strains in two hosts, they represent elite candidates for the development of a specific dual‐purpose inoculum.

Industrial sludge from the pulp‐and‐paper sector is produced in large volumes and, when properly processed, can provide low‐cost alkalinity to correct soil acidity. We evaluated the agronomic potential of a phosphorus‐rich industrial sludge as a liming amendment in two acidic soils, Subeutric Luvic Brunosol (Soil A) and Distric Luvic Brunosol (Soil B), using Medicago sativa L. under controlled greenhouse conditions. A completely randomized pot experiment combined two soils with eight treatments (control; calcite at 0.45 and 2.5 t ha −1 ; dolomite at 0.41 t ha −1 ; a Ca–Mg–S product at 0.11 t ha −1 ; sludge at 1.31, 3.90, and 10 t ha −1 ). Measured variables included seedling emergence, stem and root growth, aboveground dry biomass, and nodulation (abundance, size class, position, and internal coloration). Because several variables were non‐normal, we analyzed treatment effects within soils using Kruskal–Wallis tests with Dunn's post hoc. Sludge increased soil pH after incubation and significantly enhanced nodulation and biomass in both soils. The intermediate dose (3.90 t ha −1 ) matched or exceeded dolomite without phytotoxic responses. Responses were soil‐specific and strongest in the Subeutric Luvic Brunosol. Overall, properly processed sludge performed as a viable partial liming alternative under greenhouse conditions. Field trials are warranted to assess multi‐season agronomic consistency and confirm environmental safety at operational scales.