Crop-pasture Rotation Research Articles

Impact of cropping systems on soil quality

The agricultural intensification process implemented during the last 20 years consisted of replacing a crop-pasture rotation system with a continuous no-till cropping system that affected the functional properties of the soil in the medium term. The hypothesis of this study was that the annual cropping intensification process could be characterized, at the commercial level, by soil property indicators that capture changes in the pathway of cropping systems (CSs) in the medium term. The objectives were: i) to identify CSs based on land use; and ii) to characterize soil properties associated with different CSs. Based on this, a database was built with the land use description from 2014 to 2020 of 45 farms belonging to farmers associated with FUCREA and AUSID. A Principal Component Analysis (PCA) was performed with 14 land use indicators to select those that best summarized all the information. The selected indicators were pasture-crop ratio (PCR), soybean frequency during the summer annual cropping phase (SSbCF), intensification of annual cropping phase index (IAI), and intensity of soil use index (ISI). By performing a Cluster Analysis with these indicators, the following CSs were identified: pasture-crop rotation (ROT-PC), continuous cropping with high frequency of C4 photosynthesis species (CC_Corn), and continuous cropping with high frequency of soybean (CC_Soybean). Based on the identified CS, 64 representative sites were selected within a 60 km radius from the coordinates −33.17 S and −57.80 W, Uruguay's most influential annual cropping area, assessing 46 soil properties sensitive to changes in their management in the medium term and capable of affecting productivity. A PCA was used to select the properties that best summarized the information. A Linear Discriminant Analysis (LDA) with the selected variables and the identified CS groups determined a loss in soil fertility (organic carbon and electrical conductivity) and nutrient availability (potassium), which is related to CS diversification (CC_Soybean> CC_Corn>ROT-PC).

Pasture-crop rotations modulate the soil and rhizosphere microbiota and preserve soil structure supporting oat cultivation in the Pampa biome

Mixed systems of grain and livestock production based on pasture-crop rotations are a promising strategy to promote agriculture resilience and allow an ecological intensification of agriculture yet little is known about underlying processes in soil. To test the hypothesis that pasture-crop rotations preserve soil structure and select for beneficial soil and rhizosphere microbiota, supporting soil health and grain production, a long-term field experiment under no-tillage was studied. The experiment evaluated a gradient of land use intensities and vegetation diversities, from highly intensive continuous cropping to the least intensive system i.e. a nearby natural grassland, with two intermediate land use intensities i.e. short pasture-crop rotation and long pasture-crop rotation. Soil health was assessed based on soil physicochemical properties, microbial (Bacteria/Archaea and Fungi) community diversity and composition and oat performance. Pasture-crop rotations preserved soil bulk density and larger aggregates better than continuous cropping. High-throughput amplicon sequencing of 16S rRNA gene and ITS fragments revealed that the pasture-crop rotations fostered taxa that are associated with soil structure maintenance and selected potential plant-beneficial bacterial genera in the oat rhizosphere (i.e. Bosea, Devosia and Microbacterium), that may have contributed to the observed increase in N uptake, N accumulation and biomass in oat. In summary, this study shows that pasture-crop rotations are an ecologically sustainable alternative to continuous cropping in the Uruguayan Pampa biome.

Roots are the key for soil C restoration: A comparison of land management in the semiarid Argentinean Pampa

The objective of the study was to elucidate the relationship between soil management and carbon (C) stocks, and to identify the factors that intervene in the processes that favor C sequestration. The study was carried out on a farm in the Argentinean semiarid pampas with four land management practices (2019–2021): natural grassland (NG), crop-pasture rotation (RO), soybean monoculture (S-S) and with cover crop (S-CC). Aerial and root biomass were quantified at cover crop termination and soybean flowering. In addition, residues on soil surface were determined two times a year. In all cases, C and N contents were quantified. On composite soil samples, soil organic C (SOC), particulate C (POC), microbial biomass C and N (MBC, MBN), and soluble C and N were determined at 0–0.1 m depth. Results showed that NG had the highest and the most stable aboveground (3807.1 kg residue-C ha-1) and belowground inputs between years (4965.8 kg root-C ha-1). Similar results were observed in RO treatment during the first year (4221.0 kg root-C ha-1) diminishing by 67% after plowing for the annual crop in the second year reaching similar root-C values than S-CC and S-S (721.7 kg ha-1). S-S presented the lowest aboveground (49%) and belowground inputs (77%) compared to NG. Cover crops (S-CC) contributed with 31% and 14% of extra residue-C and root-C, respectively, compared to S-S. MBC showed a non-linear response with increases in root-C, reaching maximum carrying capacity of 110.6 ± 4.3 kg MBC ha-1 with root-C inputs ≥ 2200 kg ha-1. Our results showed significant relationships between root-C and POC and SOC, while no relationships were found for aboveground residues. Increases in soluble N explained 86% of SOC variability. Both RO and S-CC reached the “4 per Mille” goal with an average annual SOC storage rate (ΔC) of 0.24 and 0.16 Mg ha-1 y-1, respectively, while S-S had SOC losses of 0.04 Mg ha-1yr-1.

Grassland management effect on ecosystem services in the livestock system in an oxisol from the Eastern high plains of Colombia

Colombia has a livestock population of approximately 28.2 million heads, of which 20.4% is found in the eastern high plains of the Orinoquia region. The extensive beef cattle system predominates, whose diet is based on native and introduced pastures of the genus Urochloa sp. which is deficiently managed, affecting productive and reproductive indexes due to the low adoption of technology. We evaluated potential sustainable intensive systems for cattle production, which contribute to maintaining the provision of environmental services. Between 2011 and 2015 in Agrosavia’s Research Center at Carimagua (4° 37'N and 71° 19' W) environmental and animal production variables were monitored in the following systems: a) degraded pastures recovered with tillage and fertilization, b) annual crop rotation with pastures, c) forest arrangements in strips, and d) forest remnants in perimeter areas. Productive and reproductive variables were determined in animals such as weight gain, calving interval, among others while the pasture/crop productive variables included yield and forage quality. Regarding soil ecosystem services (ES) the macrofauna biodiversity, biogeochemical cycles, soil physical and chemical variables were considered. Estimation of indicators was carried out through principal components analysis for soil physical, chemical and macrofauna variables to extract the two main components that explain the variance. For climate regulation of ES, measurement of soil organic carbon (SOC) storage at a depth of 20 cm and the annual accumulated greenhouse gas (GHG) emissions were included. The systems that involved lime amendments and fertilizers increased the value in the year of application. Values in the water regulation indicator did not show significant differences among the options implemented during the years. Edaphic macrofauna biodiversity indicator value was sensitive to changes in management practices, with termites being the group with highest abundance. The indicator related to SOC was higher in the forest area compared to the pasture-crop system. Systems under the agroforestry schemes which integrated various practices such as managed and recovered pastures, crop-pasture rotation, patched areas and tree strips contributed to maintain or improve the ES, although each one of the strategies proposed provided improvement in at leas one ES.

Enhanced soil water recovery and crop yield following conversion of 9-year-old leguminous pastures into croplands

Pasture-crop rotation has been considered as an efficient agronomical practice to improve soil and water conservation, develop livestock production, and promote food security. However, the characteristics of soil water restoration and performances of crop yield and water use efficiency (WUE) after conversion of long-term leguminous pasture into croplands still remain unclear. A field experiment was conducted in China’s Loess Plateau to investigate soil water restoration and wheat yields in crop rotation with Italian ryegrass (Festuca perennis Lam.) and winter wheat (Triticum aestivum L.) converted from three 9-year-old leguminous pastures, viz. milk vetch (Astragalus adsurgens Pall.), alfalfa (Medicago sativa L.) and bush clover (Lespedeza davurica S.), and unplanted control (fallow). Soil water in the alfalfa treatment gradually recovered from up to down compared to the fallow treatment (control) during cultivation phase. After one year of rotation, the recovery levels of soil water in the three pasture-crop rotation systems at 0–500 cm soil depth were 97.1%, 95.5% and 94.2%, respectively, compared to the fallow treatment. The legume treatments significantly enhanced the crop yield (35.6%−64.5%), aboveground biomass (28.7%−59.4%) and WUE (60%−68.3%) of winter wheat compared with fallow. These results imply that the concerns about soil desiccation from long-term alfalfa was resolvable after long-term alfalfa converted into cropland in the rainfed farming area of Loess Plateau. The results also suggest that legume pasture-crop rotation can facilitate achieving a sustainable development of rainfed farming.

Management and Productivity of Key Integrated Crop–Livestock Systems in Uruguay: The Palo a Pique Long-Term Experiment’s Third Phase

Integrated Crop Livestock Systems (ICLSs) use productive diversification as a strategy to improve productivity and land use efficiency. Pasture Crop Rotations are a part of ICLSs and imply a pasture phase included in the sequence of crops. The main reasons to include pastures in crop systems are low productivity of natural grasslands and increased crop yield after a pasture phase. Our objective was to analyze the productivity indicators and management of four ICLSs that combine crop and livestock production, with data collected over a 3 y period (2019–2022). The experimental site was The Palo a Pique (Treinta y Tres, Uruguay) long-term experiment installed in 1995, located in the subtropical climate zone and on Oxyaquic Argiudolls soils (3% average slope). Systems evaluated were CC (continuous cropping), SR (two years idem CC, two years of pastures), LR (two years idem CC, four years of pastures) and FR (continuous pasture with Tall Fescue). Liveweight (LW) production, grain production and dry matter (DM) production were evaluated. Liveweight production was higher in CC and SR (426 and 418 kg LW/ha) than in LR (369 kg LW/ha) and FR (310 kg LW/ha). DM production was higher in FR and SR (6867 and 5763 kg DM/ha/year) than in LR (5399 kg DM/ha/year) and CC (5206 kg DM/ha/year). Grain production was 10%, 16% and 9% lower in soybean, wheat and sorghum in CC.

Effects of grazing, rotation, and tillage on surface runoff in a heavy textured Uruguayan soil

AbstractAdopting no‐till (NT) after conventional tillage (CT) could affect surface runoff, but this effect may also depend on the rotation type, such as continuous grain crop (CC) or crop–pasture rotation (CP). The objective of this study was to assess the effects of soil‐tillage practices and rotation type on runoff in a long‐term field (LTF) trial established in 1993 on a Mollisol. This experiment was carried from 2012 to 2017 and included three tillage rotations (NT–CP, NT–CC, and CT–CP) and a natural pasture (NP) as a control, with three replications. Runoff was monitored under natural rainfall in microplots. The pasture of the CP treatment was rotationally grazed with dairy cows at high stocking rates before this experiment. We hypothesized that soil compaction by animal trampling during grazing would increase surface runoff regardless of tillage type. We measured the number of events and runoff depth in all treatments, grain yield, soil bulk density (BD), and infiltration rate (IR) in NT–CP and NT–CC. The results showed a statistically significant increase in average runoff (107 mm yr–1) for all rotations relative to NP (68 mm yr–1) and a significant difference for the mean of both CP rotations (119 mm yr–1) compared with NT–CC (83 mm yr–1). During the crop phase (excluding the pasture), the two NT rotations showed a similar trend, but with higher BD (1.23 g cm–3) and lower IR (27.2 mm h–1) for NT–CP. We concluded that animal trampling increased surface runoff regardless of tillage, but this effect would need to be confirmed at other sites.

Soil Use Legacy as Driving Factor for Soil Erosion under Conservation Agriculture

Water erosion can cause irreversible depletions in soil quality and crop productivity. The susceptibility of the soil to erosion is affected by current and historical management practices. Historical soil management practices like ploughing or subsoil loosening may lead to irreversible degradations of soils, which in turn increases soil erosion risk. Six “Wischmeier” plots under conservation agriculture, but with different historic treatments regarding soil use and management, were evaluated. These plots were installed in 1984 in Colonia del Sacramento, Uruguay on a Vertic Argiudoll. The objective of this study was to quantify how changes in soil quality, generated by different historical soil use and management over the last 35 years, contribute to current runoff and soil erosion in a cropping system under soil conservation practices using no-till, residue retention and cover crops. Considering differences in soil legacy effects of previous land use, plots were grouped in three treatments with contrasting historic index of agricultural intensification (IAI). The IAI was developed combining the duration of land use under agricultural production and the number and intensity of tillage activity resulting in the treatments: tillage with crop-pasture rotation (TIL_CP), no-tillage under several rotations (NT_Mix) and tillage with continuous cropping (TIL_CROP) with an increasing IAI of 3.5, 7.1 and 11.8, respectively. Rainfall events, runoff water and total, fixed and volatile solids were studied from 2017 to 2019. Soil physical (bulk density, penetration resistance, infiltration rate, aggregate stability), chemical (soil organic carbon (SOC), pH, phosphorous (P-Bray)) and biological properties (particulate organic matter (POM), potentially mineralizable nitrogen (PMN)) were assessed in 2019. Yearly average runoff amounted 209, 579 and 320 mm in 2017, 2018 and 2019, respectively. Yearly average soil losses were 233, 805 and 139 kg/ha with significant differences among years. The lowest soil losses were observed in TIL_CP (231, 615 and 146 kg/ha in 2017, 2018 and 2019, respectively) with lowest IAI of 3.5. Infiltration rate was the lowest in plots with highest IAI. Soil bulk density was highest (1.3 g/cm3) in plots with high IAI. SOC and PMN were lowest in TIL_CROP (3.0% SOC and 34 mg/kg PMN), holding the highest IAI of 11.8. Conservation agriculture minimized soil erosion losses in all plots and years, and erosion was much lower than the maximum tolerable threshold of 7,000 kg/ha for this particular soil. However, in historically intensively tilled and cropped soils, soil quality showed long-term adverse effects pointing towards a reduced resilience of the agricultural system.

Nitrous Oxide Mitigation from an Integrated System Based on Pasture–Crop Rotation with Two Levels of P and K Fertilization

Nitrous Oxide Mitigation from an Integrated System Based on Pasture–Crop Rotation with Two Levels of P and K Fertilization

Management Zones Delineation: A Proposal to Overcome the Crop-Pasture Rotation Challenge

Management Zones Delineation: A Proposal to Overcome the Crop-Pasture Rotation Challenge

Nitrogen nutrition index at GS 3.3 is an effective tool to adjust nitrogen required to reach attainable wheat yield

Current nitrogen (N) fertilization schedule for spring wheat was developed under a dominant crop-pasture rotation. After the year 2002, this cropping system was converted to continuous annual cropping systems under no-till, reducing soil N supply capacity progressively. Additionally, highest grain yield of new varieties increased N demand. The required additional N fertilizer can be adjusted by monitoring nutritional status of the crop. Our objectives were: i) to determine optimal N status at different phenological stages; ii) to quantify the wheat yield gap explained by N supply deficit, and iii) to assess the critical nitrogen nutrition index (NNI) value as a predictor of response to N fertilizer applied at GS 3.3. We adjusted the nitrogen dilution curve (Nc=4.17DM-0.31), deriving a critical NNI at GS 3.3 (NNI=1.24). Depending on soil N supply capacity and NNI at GS 3.3, wheat yield gap attributed to N supply deficit varied from 0 to 2.74 Mg ha-1, averaging 0.76 Mg ha-1. The critical NNI proposed at GS 3.3 was effective to diagnose the N crop demand to reach the attainable yield under different scenarios.

Corrigendum to: Ecosystem dynamics of crop–pasture rotations in a fifty‐year field experiment in southern South America: Century model and field results

Soil Science Society of America JournalVolume 85, Issue 5 p. 1866-1866 CORRIGENDUMFree Access Corrigendum to: Ecosystem dynamics of crop–pasture rotations in a fifty-year field experiment in southern South America: Century model and field results This article corrects the following: Ecosystem dynamics of crop–pasture rotations in a fifty-year field experiment in southern South America: Century model and field results Walter E. Baethgen, William J. Parton, Valentina Rubio, Robin H. Kelly, Susan M. Lutz, Volume 85Issue 2Soil Science Society of America Journal pages: 423-437 First Published online: March 24, 2021 First published: 28 September 2021 https://doi.org/10.1002/saj2.20316AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL In the original publication (Baethgen et al., 2021), Table 1 contains incorrect data. A corrected version of the table is presented below. The authors apologize for this error. TABLE 1. Century model simulation for 100 yr in CS2 and CS5, for five scenarios: (a) using a sequence with 3 yr of pastures followed by 3 yr of annual crops (C3P3); (b) using a sequence of 6 yr of crops and 3 yr of pastures (C6P3); (c) using a sequence of 9 yr of crops and 3 yr of pastures (C9P3); (d) using a sequence of 4 yr of crops including cover crops (CC); and (e) using a sequence of only annual crops (CONT—no pastures and no cover crops). Results are shown for the average grain yields during grain producing years, total grain production during a 100-yr time period, total C inputs from aboveground plant biomass during a 100-yr time period, and total C inputs from belowground biomass during the 100-yr time period Avg. grain yield Total grain production Total C input abovegrounda Total C input belowgroundb Scenario g C m−2 yr−1 g C m−2 in 100 yr CS2 (a) 175 12,655 20,558 12,613 CS2 (b) 142 13,071 19,441 11,178 CS2 (c) 136 13,663 19,643 10,907 CS2 (d) 130 15,486 17,823 9,280 CS2 (e) 96 11,975 15,647 8,221 CS5 (a) 196 14,210 22,426 14,030 CS5 (b) 161 14,757 21,704 12,378 CS5 (c) 144 14,368 20,567 11,434 CS5 (d) 140 16,644 19,365 10,084 CS5 (e) 100 12,518 16,480 8,631 a Crop stover + pasture + cover crops (i.e., all biomass that remained on soil) in 100 yr. b Total root biomass produced in 100 yr. REFERENCE Baethgen, W. E., Parton, W. J., Rubio, V., Kelly, R. H., & Lutz, S. M. (2021). Ecosystem dynamics of crop–pasture rotations in a fifty-year field experiment in southern South America: Century model and field results. Soil Science Society of America Journal, 2021, (85), 423– 437. https://doi.org/10.1002/saj2.20204 Volume85, Issue5September/October 2021Pages 1866-1866 ReferencesRelatedInformation

Forage Species Identity Shapes Soil Biota in a Temperate Agroecosystem

Increasing plant diversity in the perennial phase of pasture-crop rotations is predicted to positively affect belowground productivity and microbial communities and, in turn, augment belowground agroecosystem services including soil health and carbon storage. Using two grass and one legume forage species grown as monocultures and combined in four intercropped combinations, we evaluated how species identity and richness influence belowground productivity, soil microbial communities, and soil C pools. Though grass-legume intercrops demonstrated higher aboveground productivity than component species grown in monoculture, higher species richness was not associated with increased productivity belowground. Root biomass was greatest in tall fescue (Festuca arundinacea Schreb.) monoculture, and intercrops including this species. Species identity was similarly associated with soil microbial community attributes. Orchardgrass (Dactylis glomerata L.) monoculture exhibited lower total microbial abundance and lower bacterial abundance than grass-legume intercrops. Bacterial abundance was also lower in orchardgrass compared to white clover (Trifolium repens L.) monoculture. A common indictor of soil function, the fungal:bacterial ratio, was higher in grass-only than clover-only stands. The prevalence of species-specific impacts on roots and microbial communities in this study suggests that species identity may have a stronger influence than species richness on belowground agroecosystem services from perennial forages in temperate regions.

Ecosystem dynamics of crop–pasture rotations in a fifty‐year field experiment in southern South America: Century model and field results

AbstractThe Century model was used to simulate soil C and N cycling and crop production dynamics in an ongoing field experiment in Uruguay (started in 1963). The model was calibrated using observed data from three treatments (crop or crop–pasture rotations) and validated with a fourth treatment. The model correctly predicted the impact of different treatments on microbial biomass, N mineralization, soil respiration, and crop yields. The model and observed data show that soil respiration, N mineralization, soil C, and crop yields increase with increasing plant‐derived C inputs caused by increasing the frequency of pastures in the rotations. This is one of the first papers that show the strong positive correlation of observed soil C with plant C soil inputs to field‐observed microbial biomass, soil respiration, and N mineralization. The results also showed that reducing tillage and transitioning to a no‐till system increased soil C and reduced soil erosion. The main path of soil C losses was heterotrophic microbial respiration, which accounted for 66% of the total C lost in a continuous crop rotation and no fertilizers, 71% in a continuous crop rotation with fertilizers, and 86% in a crop–pasture rotation with fertilizers. Model results from a degraded cropping system showed that adding grass–clover (Trifoliumspp.) pastures greatly increased plant production and soil C, whereas reducing the frequency of grass–clover pastures in high‐fertility cropping systems from 50% of the time to 25% reduces crop yields and soil C. Including cover crops substantially increases crop production and maintains soil C in high‐fertility and degraded cropping systems.

Improving soil properties and productivity of crop-pasture rotation in arid steppe of the Southern Urals

Field experiments were conducted in the arid steppe zone of the Southern Urals, in the Republic of Bashkortostan of the Russian Federation. The soil is common chernozem. The precipitation during the growing season (May-September) is 166 mm. The experimental crop rotation consisted of 7 fields: 4 with perennial herbs (a mixture of Bromus inermis and Medicago varia), 3 with annual crops. The study analysed soil properties and carrying capacity in perennial grass rotation, conventional and reduced tillage. During the crop-pasture rotation, the humus content in the soil changes insignificantly depending on the tillage, being within 7.6-8.0 %. Perennial grasses loosened the soil, positively affecting moisture accumulation under crop rotation by the beginning of the pre-sowing period. The arable layer of common chernozem in the reduced tillage had a density of 1.05 g/cm3, less than 0.06 g/cm3 in conventional cultivation. Fertilizer application increased yields at 0.49-0.51 t/ha of feed units. Reduced tillage resulted in higher feed units by 0.06-0.08 tons per 1 ha. Crop-pasture rotation implementation and development ensures bioclimatically-determined yields of fodder crops and maintains soil fertility at an optimal level.

The dos and don'ts of no-till continuous cropping: Evidence from wheat yield and nitrogen use efficiency

Abstract When crop-pasture rotation is converted to a single fallow/soybean or winter crop/soybean annual cropping, wheat grain yield declines progressively as the annual cropping phase lengthens, regardless of the tillage system. This decline can be attributed to i) depletion of the soil nutrient supply capacity and ii) subtle but cumulative degradation of soil physical properties. The objectives of this study were to disentangle and quantify the limitations on wheat yield imposed by these processes, and to identify the cropping sequence that preserves soil quality and enables high wheat yield. Wheat was grown for two years at three nitrogen (N) fertilization rates (0, 80 and 190 kg ha−1) in soils after a 20-years experiment with six cropping systems. The cropping systems are crop-pasture rotations with tillage (ROT_CT) or no-till (ROT_NT), continuous cropping with no-till and high frequency of sorghum and maize (CC_NTC4) or soybean and sunflower (CC_NTC3) or winter fallow (CC_NTWF), and continuous annual cropping under conventional tillage (CC_CT). Soil quality was assessed based on chemical (soil organic carbon, total soil N concentration and potentially mineralizable N) and physical properties (field water infiltration rate and soil aggregate stability). In each system, we estimated the yield gap due to N supply ( Y g N ) limitations and the yield gap due to soil properties other than N supply limitations ( Y g o t h e r s ), so that the total yield gap ( Y g T ) is the sum of Y g N and Y g o t h e r s . Systems that degraded chemical and physical properties had lower yield, grain N concentration and fertilizer N use efficiency (NUEf, kg of grain kg−1 of N added). Only two systems, ROT_NT and CC_NTC4, achieved Y m a x (7.2 Mg ha-1). For these two systems Y g T = Y g N . For the other systems, the percentage of Y g T explained by Y g o t h e r s varied between 23 % and 50 %. Rotations that increased the soil N supply (N uptake with no N fertilizer) also increased NUEf. Wheat under ROT_NT reached the maximum yield obtained under CC_CT with 45 % less N fertilizer (104 vs 190 kg ha−1) and higher NUEf (50 vs 27 kg kg−1). Comparing ROT_NT and CC_NTC4 to other continuous no-till cropping systems (CC_NTWF and CC_NTC3), the N fertilizer required was increased from 104 and 107 to 152 and 163 kg ha-1, respectively. In conclusion, rotating annual crops under no-till is not enough to preserve soil productivity. Sustainable intensification under continuous no-till would require either re-balancing crop sequences towards crop-pasture rotations or a shift towards a lower frequency of soybean in favor of higher frequency of maize and sorghum in the summer phase of the rotation.

Soil management and environmental sustainability of crop-livestock systems

Uruguay experienced an expansion of the cropped area in the last decades motivated by market conditions: price of grains, differences in the relative land value, and regional tax policies. This change affected the crop-livestock production system, mainly in soil quality and system sustainability. The available information on soil erosion and organic carbon content (soc) allowed to validate the models usle/rusle and century, which demonstrated the advantages of crop-pasture rotations compared to continuous cropping. No-till represented an outstanding advance, by reducing mechanical tillage. The drop in soil organic carbon was correlated with a productivity decrease, mainly due to the lower availability of nutrients and limitations in the physical properties of the soil. The Global Soil Alliance of fao highlights the three most important threats on sustainable soil management: erosion, loss of organic carbon, and nutrient imbalance. The main public policy in Uruguay is the application of the Law of Soil and Surface Water Conservation. The principal measure is that cropping cannot present erosion estimates above the official tolerance for the dominant soil used. It became mandatory in 2013, and currently, 96% of the obliged area has complied with the presentation of the plans, covering 1.6 Mha. In 2018, a proposal for the Environmental Plan for Sustainable Development based on agroecology elements was generated from the Environmental Ministerial Office. Crop-pasture rotations include varied plant and animal production, and comply with most agroecology elements, minimizing erosion and maintaining or recovering soc.

Distinct controls over the temporal dynamics of soil carbon fractions after land use change.

Soil organic carbon (SOC), the largest terrestrial carbon pool, plays a significant role in soil-related ecosystem services such as climate regulation, soil fertility and agricultural production. However, its fate under land use change is difficult to predict. A major issue is that SOC comprised of numerous organic compounds with potentially distinct and poorly understood turnover properties. Here we use spatiotemporal measurements of the particulate (POC), mineral-associated (MOC) and charred SOC (COC) fractions from 176 trials involving changes in land use to assess their underlying controls. We find that the initial pool sizes of each of the three fractions consistently and dominantly control their temporal dynamics after changes in land use (i.e. the baseline effects). The effects of climate, soil physicochemical properties and plant residues, however, are fraction- and time-dependent. Climate and soil properties show similar importance for controlling the dynamics of MOC and COC, while plant residue inputs (in term of their quantity and quality) are much less important. For POC, plant residues and management practices (e.g. the frequency of pasture in crop-pasture rotation systems) are substantially more important, overriding the influence of climate. These results demonstrate the pivotal role of measuring SOC composition and considering fraction-specific stabilization and destabilization processes for effective SOC management and reliable SOC predictions.

Carryover of N-fertilization from corn to pasture in an integrated crop-livestock system

ABSTRACT Nutrient-use efficiency in pasture-crop rotations is not well understood. The hypothesis of this research is that nitrogen (N) cycled from the corn crop to the following pasture is not enough to supply the N demand of the pasture, independent of pasture height management. Our goal was to assess the carryover effect of N-fertilization from corn crop to a mixed pasture of black oat and ryegrass managed with two sward heights in an integrated crop-livestock system. The experimental design was a factorial arrangement (2 × 2) of sward height (10 and 25 cm) and N pasture fertilization: 0 kg N ha−1 (representing the carryover of N-fertilization from the corn crop) and 200 kg N ha−1. Accumulated forage dry matter and N concentration increased by 62% and 40%, respectively, in the pasture-fertilized compared with fertilization only in the previous crop phase. The residual effect of N applied to the previous corn crop was not enough to adequately meet the N requirements of the subsequent pasture, thereby reducing forage dry matter accumulation compared with the pasture-fertilized system. Our data suggest that fertilization of the pasture phase is key to better nutrient use efficiency in integrated crop-livestock systems.

The ‘Palo a Pique’ Long-Term Research Platform: First 25 Years of a Crop–Livestock Experiment in Uruguay

Mixed crop–livestock long-term experiments (LTE) are critical to increase the understanding of sustainability in complex agroecosystems. One example is the ‘Palo a Pique’ LTE which has been running for 25 years in Uruguay (from 1995 to present), evaluating four pasture–crop rotations under livestock grazing with no-till technology in soils with severe limitations. The results demonstrate that cropping systems reduced soil organic carbon (SOC) compared with permanent pastures, and that perennial pastures rotating with crops were critical to mitigate SOC losses. Data from the ‘Palo a Pique’ LTE has contributed to the establishment of new national policies to secure the sustainability of agricultural-based systems. Although the original purpose of the LTE was oriented to crops and soils, a demand for sustainable livestock intensification has gathered momentum over recent years. As a result, the current approach of the ‘Palo a Pique’ LTE matches each pasture–crop rotation with the most suitable livestock strategy with the common goal of producing 400 kg liveweight/ha per year. General approaches to the pursuit of sustainable livestock intensification include shortening the cycle of production, diversifying animal categories, increasing liveweight gain and final animal liveweight, and strategic livestock supplementation. Prediction of trade-offs between environmental, economic, and production indicators can be addressed through monitoring and modeling, enabling the timely anticipation of adverse sustainability issues on commercial farms. The ‘Palo a Pique’ LTE serves as a framework to address contemporary and future questions dealing with the role of ruminants on climate change, competition for land, nutrient dynamics, and food security.