The agricultural industry has an opportunity to shift to a more sustainable practice that helps restore vital topsoil, improve water quality, reduce environmental impact, and sequester atmospheric carbon into the vast soil carbon pool. However, to implement these practices at considerable scale, agricultural producers require access to resources and capital they rarely have and can be difficult to acquire. As a company, investing in regenerative agriculture in supply chains can lead to reduced Scope 3 emissions, more resilient supply chains, and better marketability as an investment fund, an employer, and a brand. Insetting regenerative agriculture can protect supply chains against climate risks and productivity loss, as well as serve as a more secure alternative to carbon credit offsets. Four successful companies, General Mills, Organic Valley, Nestlé, and Nespresso, have been shown to benefit from investing in regenerative agriculture as part of their evolution towards reaching net zero emissions. Based on their strategies, this paper has developed a recommended framework for programming investments for insetting regenerative agriculture. The recommendations rest on six pillars: 1) determining impact, 2) providing direct support to farmers, 3) place-specific strategies, 4) collaboration through partnerships, 5) scalable programming, and 6) educate consumers. Together, these represent a comprehensive approach to insetting that will provide long-term benefits to businesses, suppliers, and the planet.

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Soil organic matter (SOM) is a well known indicator of soil quality due to its direct influence on soil properties such as structure, soil stability, water availability, cation exchange capacity, nutrient cycling, and pH buffering and amelioration. Study sites were selected in the Valley region of Virginia with the study objectives to: i) compare the efficiency of density solutions used in recovering free-light fraction (FLF) organic matter; ii) compare different soil organic fractions as sensitive indices of short-term changes in SOM due to management practices; iii) investigate on-farm effects of tillage management on soil organic carbon (SOC) and soil organic nitrogen (SON) stocks; and iv) evaluate the role of SOM in controlling soil available nitrogen (N) for corn uptake. The efficiency of the density solutions sodium iodide (NaI) and sodium polytungstate (SPT) in recovering FLF was the same at densities of 1.6 and 1.8 g cm⁻³, with both chemicals presenting less variability at 1.8 g cm⁻³. The sensitivity of SOM fractions in response to crop and soil management depended on the variable tested with particulate organic matter (POM) being the most sensitive when only tillage was tested, and FLF being the most sensitive when crop rotation and cover crop management were added. The on-farm investigation of tillage management on stocks of SOC and total soil N (TSN) indicated significant increases at 0–15 cm depth by increasing the duration (0 to 10 years) of no-tillage (NT) management (0.59 ± 0.14 Mg C ha⁻¹ yr⁻¹ and 0.05 ± 0.02 Mg N ha⁻¹ yr⁻¹). However, duration of NT had no significant effect on SOC and TSN stocks at 0–60 cm depth. Soil available N as controlled by SOM was modeled using corn (<i>Zea mays</i> L.) plant uptake as response and several soil N fractions as explanatory variables. The final model developed for 0–30 cm depth had 6 regressors representing the different SOM pools (active, intermediate, and stable) and a 𝑅² value of 65%. In summary, this study provides information about on-farm management affects on SOM levels; measurement of such effects in the short-term; and estimation of soil available N as related to different soil organic fractions. / Ph. D.

Much of Haitian agriculture is characterized by subsistence farming systems on eroded and nutrient-poor soils. Implementation of Conservation Agriculture systems has proven effective at improving soil quality and crop yield in many areas of the world, including areas similar to those in Haiti. While most Haitian smallholder farmers are highly resource-limited and adoption of new technologies is limited, these farmers are known to adopt new crops and practices if benefits that outweigh risks are demonstrated. Cover crops that help provide soil cover and increase nutrient mineralization are one of the most potentially beneficial changes that could be made on most smallholder farms. However, before specific cover crop recommendations can be made, their potential benefits need to be quantified. One field experiment in the summer of 2013 assessed decomposition rates and nutrient mineralization from common cash crops and two potential cover crops either on the soil surface or buried at 15 cm. The relative difficulty and expense of conducting these types of field trials led to the development and assessment of a laboratory-based system that could be used to simulate plant residue decomposition and nutrient release under controlled conditions. Additional benefits of a laboratory-based study include the ability to test significantly more treatment combinations than would likely be possible under field conditions and to control nearly all other experimental variables, other than the desired treatment comparisons. / Master of Science

Current Virginia nitrogen (N) fertilizer recommendations do not include site-specific estimates of N supply from cover crops (CCs) or soil organic matter (SOM). Recent research successfully predicted the contribution of N from SOM and CCs to corn (Zea mays L.) in Pennsylvania. The objective of this work was to validate the biophysical model developed in Pennsylvania under Virginia conditions and to evaluate the decomposition rates of different surface-applied CC residues and the relationship between their chemical composition and decomposition rate. For the first objective, 83 N response trials were conducted in different regions of Virginia across 9 years using a randomized complete block design with four replications. The model was able to explain 47% and 15% of variability in unfertilized corn yield (RMSE = 1.6 Mg ha-1) and economical optimum N rate (EONR) (RMSE = 30 kg N ha-1) respectively. Efforts to improve the model by adding economically unresponsive sites improved the model performance to explain 45% of the variability in EONR. For the second objective, a lab incubation was performed to compare carbon (C) and N mineralization from four different CCs {Cereal Rye (CR), Hairy vetch (HV), Crimson clover (Cc) and Rapeseed (R)} on a sandy loam soil. Destructive sampling was performed at 6 different sampling dates – 3, 7, 14, 28, 56 and 112 days. ANOVA test revealed that the effects of CC species, incubation days and their interaction had a significant effect on mass decomposed, plant biochemical composition and net N mineralization. Variation in mass loss was positively related to lignin content for all the CCs while it was moderately correlated to C:N ratio for CR and R and weakly to HV and Cc. Biomass loss and N release was highest in HV followed by Cc, R and CR. Net N mineralization was highest in HV followed by R, Cc and CR amended soils. / Master of Science / Current Virginia nitrogen (N) fertilizer recommendations do not include site-specific estimates of N supply from cover crops or soil organic matter, both of which can influence crop N need. Recent research successfully predicted the contribution of N from cover crops and soil to corn (Zea mays L.) in Pennsylvania. The objectives of this work were to validate the biophysical model developed in Pennsylvania under Virginia conditions and to evaluate the decomposition rates of different surface-applied cover crop residues and the relationship between their chemical composition and decomposition rate. The Pennsylvania-developed model was able to successfully estimate the economical optimum N rate for corn and predict the yield of unfertilized corn. Corn yield did not increase with increasing N rates in some fields. When these sites were omitted, the accuracy of the model improved. For the second objective, a lab incubation study was performed comparing C and N released from Cereal Rye (CR), Hairy vetch (HV), Crimson clover (Cc) and Rapeseed (R)} on a sandy loam soil. Destructive sampling was performed at 6 different sampling dates – 3, 7, 14, 28, 56 and 112 days. Variation in mass loss was positively related to lignin content for all the cover crops while it was moderately correlated to C:N ratio for CR and R and weakly to HV and Cc. Biomass loss and N release was highest in HV followed by Cc, R and CR.

This research investigated the long-term effects of transitioning from intensive tillage to no-till (NT) practices with cover crop (CC) incorporation on soil quality, agronomic performance, and economic returns in Virginia's Coastal Plain. Nine years after integrating NT practices and CCs, improvements in soil physical and chemical properties were observed, including a 22% to 65% increase in soil organic matter (SOM) in the top 5 cm, a 4% reduction in bulk density, and enhanced soil moisture retention in corn production. Timing of CC termination played a crucial role in optimizing biomass production and nutrient accumulation. Overall accumulation rates were 44.4 kg dry biomass ha-1 d-1, 1.22 kg N ha-1 d-1, 0.16 kg P ha-1 d-1, 1.36 kg K ha-1 d-1, and 0.08 kg S ha-1 d-1 of delayed termination between March 15 and April 30. Each additional day of cover crop growth contributed to a fertilizer value of $3.91 ha-1, highlighting the economic advantage of extending CC growth during this critical period. In 2023, CC effects on corn N fertilizer demand and yields were assessed by applying variable N rates of 0, 56, 112, and 168 kg N ha-1 at sidedressing. Greatest corn yields at each N rate were observed following hairy vetch and a vetch-dominant CC mix, which had low C:N ratios (≤12:1) and accumulated 134 to 186 kg N ha-1 in their aboveground biomass. Corn yields after these CCs were 8.5 to 9.3 Mg ha-1 at the zero N sidedressing rate, increasing to 10.8 to 11.3 Mg ha-1 at the 168 kg N ha-1 rate. However, increasing the N rate yielded minimal economic benefits for these treatments. Vetch treatments produced the highest net returns, with greater returns at lower N rates, as vetch generated an additional US$1,012 ha-1 at the zero N sidedressing rate compared to the no CC control. Conversely, cereal rye produced a negative net return across all N rates, with positive returns achievable only with state cost-share payments. The findings underscore the importance of adaptive N management strategies and policy adjustments to support environmentally and economically sustainable cover crop practices in corn production. / Doctor of Philosophy / This research examines long-term benefits of switching from intensive tillage to no-till (NT) farming with cover crops (CC) on soil health, crop performance, and economic returns in Virginia's Coastal Plain. After nine years of using NT and CCs, we saw significant improvements in soil quality: soil organic matter in the top 5 cm increased by 22% to 65%, bulk density decreased by 4%, and soil moisture retention improved in corn crops. The timing of cover crop termination was crucial for maximizing biomass and nutrient benefits. Delaying termination from March 15 to April 30 resulted in additional dry biomass and nutrients, translating into a fertilizer value of $3.91 per hectare for every day of extra growth. In 2023, we assessed how different nitrogen (N) rates affected corn yields and fertilizer needs. Best yields were achieved with hairy vetch and vetch-dominant cover crops, which had low carbon-to-nitrogen (C:N) ratios and accumulated significant N in their biomass. Although these cover crops improved yields, increasing N rates returned minimal economic gains. Vetch treatments provided the highest net returns, especially at lower N rates, generating an additional $1,012 per hectare compared to no cover crop. In contrast, cereal rye resulted in negative returns across all N rates, unless state cost-share payments were applied. These results highlight the need for flexible N management strategies and policy changes to support effective and profitable cover crop practices in corn farming.

Soils are the largest pool of carbon (C) in terrestrial ecosystems and store 1500 Gt of C in their soil organic matter (SOM). SOM is a dynamic, complex and heterogeneous mixture, which influences soil quality through a wide range of soil properties. Labile SOM comprises a small fraction of total SOM (approximately 5%), but due to its rapid turnover has been suggested to be most vulnerable to loss following soil disturbance. This research was undertaken to examine the consequences of soil disturbance on labile SOM, its availability and protection in soils using the isotopic analysis of soil-respired CO₂ (δ¹³CO₂). A range of soils were incubated in both the short- (minutes) and long-term (months) to assess changes in labile SOM. Shifts in soil-respired δ¹³CO₂ over the course of soil incubations were found to reflect changes in labile substrate utilisation. There was a rapid depletion of δ¹³CO₂ (from a starting range between -22.5 and -23.9‰, to between -25.8 and -27.5‰) immediately after soil sampling. These initial changes in δ¹³CO₂ indicated an increased availability of labile SOM following the disturbance of coring the soil and starting the incubations. Subsequently δ¹³CO₂ reverted back to the initial, relatively enriched starting values, but this took several months and was due to labile SOM pools becoming exhausted. A subsequent study was undertaken to test if soil-respired δ¹³CO₂ values are a direct function of the amount of labile SOM and soil physical conditions. A range of pasture soils were incubated in the short-term (300 minutes), and changes in soil-respired δ¹³CO₂ were measured along with physical and chemical soil properties. Equilibrium soil-respired δ¹³CO₂, observed after the initial rapid depletion and stabilisation, was a function of the amount of labile SOM (measured as hot water extractable C, HWEC), total soil C and soil protection capacity (measured as specific soil surface area, SSA). An independent experimental approach to assess the effect of SSA, where labile SOM was immobilised onto allophane – a clay mineral with large, active surface area – indicated limited availability of labile SOM through more enriched δ¹³CO₂ (in a range between -20.5 and -20.6 ‰) and a significant (up to three times) reduction in HWEC. In the third study, isotopic measurements were coupled with CO₂ evolution rates to directly test whether equilibrium soil-respired δ¹³CO₂ can reflect labile SOM vulnerability to loss. Soils were sampled from an experimental tillage trial with different management treatments (chemical fallow, arable cropping and permanent pasture) with a range of C inputs and soil disturbance regimes. Soils were incubated in the short- (300 minutes) and long-term (600 days) and changes in δ¹³CO₂ and respiration rates measured. Physical and chemical fractionation methods were used to quantify the amount of labile SOM. Pasture soils were characterised by higher labile SOM estimates (HWEC; sand-sized C; labile C respired during long-term incubations) than the other soils. Long-term absence of plant inputs in fallow soils resulted in a significant depletion of labile SOM (close to 50% based on sand-sized C and HWEC estimates) compared with pasture soils. The values of δ¹³CO₂ became more depleted in 13C from fallow to pasture soils (from -26.3 ‰ to -28.1 ‰) and, when standardised (against the isotopic composition of the solid soil material), Δ¹³CO₂ values also showed a decrease from fallow to pasture soils (from -0.3 ‰ to -1.1 ‰). Moreover, these patterns in isotopic measures were in strong agreement with the amount of labile SOM and its availability across the soils, and were best explained by the isotopic values of the labile HWEC fraction. Collectively, these results confirm that labile SOM availability and utilisation change immediately after soil disturbance. Moreover, isotopic analysis of soil-respired CO₂ is a powerful technique, which enables us to probe mechanisms and examine the consequences of soil disturbance on labile SOM by reflecting its availability and the degree of SOM protection.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The cattle breeding and crop production integrated systems in the south of Brazil is based mostly on grain production with summer crops and beef cattle production over winter pastures. This activity have been expanded quickly in the state of Rio Grande do Sul, due the increase of soybean cultivation over native grass fields areas and the requirement to improve the livestock productivity index in that state. However, few research works exists until this moment to show the best management systems to this areas mainly due to its distinct character of agriculture and livestock when are isolated activities. With this meaning, this work has the purpose to evaluate the effect in increase use intensity of winter pastures and different summer crops systems over the soil organic matter (SOM) dynamics and its granulometric fractions particulate and mineral associated SOM on this areas and the grain and beef cattle yield achieved. For that, a field experiment was carried out over a Palehudult soil, on the city of Jari RS, with complete randomized blocks experimental design on factorial treatment distribution, four replications, with the utilization of three winter pastures management systems: no grazing (NG), grazing even 28 days (G28) and grazing even 14 days (G14), composing in this way increasing grazing frequencies over that pastures; and three summer crops systems: soybean monoculture (Mon-S), corn monoculture (Mon-C) and soybean/corn rotation (Rot-S/C). The beef cattle yield during the winter was not significantly affected by the increase of the grazing frequencies, but the biomass production to soil cover by the pastures and the grain yield of summer crops was reduced when the use intensity of the winter pastures by the animals was increased. The C addition to the soil by vegetal residues varied between 2.92 and 7.59 Mg ha-1 year-1 to the treatments G14 Mon-S and NG Mon-M, respectively. So, the main SOM fraction affected by the employed management in each treatment was the particulate fraction, expressed by the POM-C pool. This pool showed be 49 times more sensitive to the applied management over the winter pastures than the mineral associated fraction, expresses by the AMOM-C pools. The application of the Hennín & Dupuis s mathematical model to the prediction of each pools of SOM showed higher turnover rates of POM-C, in relation to the SOC and AMOM-C pools. The k1 coefficient (humification rate of the C additioned to the soil) obtained by the mathematical model was 0.1215, 0.0936 and 0.1249 year-1, to POM-C, AMOM-C and SOC, respectively, while the k2 coefficient (mineralization rate of de SOC) was 0.1292, 0.0161 and 0.0185 year-1, to the same pools. Using this data, the POM-C and SOC simulated pools on stability were 2.75 and 19.73 Mg ha-1, respectively, to the treatment G14 Mon-S, and 7.13 and 51.21 Mg ha-1, respectively, to the treatment NG Mon-M. The t½ (half-life time) for POM-C, AMOM-C and SOC were 5, 43 and 37 years, respectively, and the MRT (mean residence time) were 8, 62 and 54 years, to the same pools, respectively. The treatments that not received grazing during the winter showed good potential to the atmospheric CO2 sequestration, while the increase of the grazing intensity reduced this potential, passing to actuate like a sink of atmospheric CO2 when the G28 and G14 frequencies had been applied. The POM-N pools had been equally more sensitive to the grazing and crop management applied than the AMOM-N or TN pools, being that the higher pools had been observed when soybean was utilized on monoculture over the areas that not received grazing and the lowers pools had been observed when the corn was cultivated on monoculture over areas that received grazing even 14 days during the winter. / A Integração Lavoura-Pecuária no sul do Brasil baseia-se principalmente na exploração de culturas produtoras de grãos, durante o verão, e na produção de carne bovina sobre pastagens de estação fria, durante o inverno. Esta atividade vem se expandindo rapidamente no Rio Grande do Sul, devido ao aumento da área de cultivo da soja sobre áreas de campo nativo e da necessidade de se melhorar os índices de produtividade da pecuária neste estado. No entanto, pouco trabalhos de pesquisa existem até o momento, a fim de indicar quais os melhores sistemas de manejo destas áreas, tendo em vista seu caráter distinto da agricultura e da pecuária quando atividades isoladas. Neste sentido, este trabalho tem por objetivo avaliar a influência do aumento da intensidade de utilização das pastagens de inverno e diferentes sistemas de culturas de verão sobre a dinâmica da MOS e de suas frações granulométricas particulada e associada a minerais nestas áreas, bem como a produtividade de grãos e de carne alcançadas. Para tanto instalou-se um experimento a campo sobre um Argissolos Vermelho-Amarelo Alumínico típico, no município de Jari RS, com delineamento experimental blocos ao acaso com parcelas dispostas em distribuição fatorial, com quatro repetições, que constou da utilização de três sistemas de manejo das pastagens de inverno, que eram compostas de Aveia Preta e Azevém, sendo eles: sem pastoreio (SP), pastoreio a cada 28 dias (P28) e pastoreio a cada 14 dias (P14), compondo assim freqüências crescentes de pastoreio sobre estas pastagens; e três sistemas de culturas de verão, a saber: monocultura de soja (Mon-S), monocultura de milho (Mon-M) e rotação soja/milho (Rot-S/M). Observou-se que o ganho de peso vivo animal durante o inverno não foi significativamente beneficiado pelo aumento da freqüência de pastoreios, porém a produção de fitomassa para cobertura de solo pelas pastagens e o rendimento de grãos da culturas de verão foi reduzido quando aumentou-se a intensidade de utilização das pastagens de inverno pelos animais. As adições de C ao solo via resíduos vegetais variou entre 2,92 e 7,59 Mg ha-1 ano-1, para os tratamentos P14 Mon-S e SP Mon-M, respectivamente. A principal fração da MOS afetada pelo manejo empregado em cada tratamento foi a fração particulada (COp), sendo que os estoques de CO nesta fração se mostraram 49 vezes mais sensíveis ao manejo aplicado sobre as pastagens de inverno do que a fração associada a minerais (COam). A aplicação do modelo matemático unicompartimental de Hennín & Dupuis para a modelagem dos estoques de cada fração da MOS demonstrou a maior velocidade de ciclagem do COp, em relação aos estoques de COT e COam. O coeficiente k1 (taxa de humificação do C adicionado ao solo) do modelo matemático obtidos foram de 0,1215, 0,0936 e 0,1249 ano-1, para o COp, COam e COT, respectivamente, enquanto que o coeficiente k2 (taxa de mineralização do CO) foram de 0,1292, 0,0161 e 0,0185 ano-1, para os mesmos compartimentos da MOS. Utilizando estes dados, simulou-se que os estoques de COp e COT na camada 0 -10 cm na estabilidade serão de 2,75 e 19,73 Mg ha-1, respectivamente, para o tratamento P14 Mon-S, e de 7,13 e 51,21 Mg ha-1, respectivamente, para o tratamento SP Mon-M. Além disto, o t½ (tempo de meia vida) do COp, COam e COT calculados foram de 5, 43 e 37 anos, respectivamente, e o TMP (tempo médio de permanência) calculados foram de 8, 62 e 54 anos, para os mesmos compartimentos, respectivamente. O solo nos tratamentos que não receberam pastoreios durante o inverno apresentaram bom potencial para seqüestro de CO2 atmosférico, enquanto que o aumento da intensidade de pastoreios reduziu este potencial, passando a atuar como fonte de CO2 para a atmosfera quando aplicou-se a maior freqüência de pastoreios. Os estoques de NTp foram também mais sensíveis ao manejo do pastoreio e de culturas do que os estoques de NTam ou NT, sendo que os maiores estoques foram observados quando utilizou-se a soja em monocultivo nas áreas que não receberam pastoreio e os menores quando o milho foi cultivado em monocultura em áreas que receberam uma freqüência de pastoreio de 14 dias no inverno.

A loss of soil organic matter (SOM), whether through natural means or management practices, results in soil degradation. Biochar as a soil amendment can alter soil properties, ultimately affecting the availability of nitrogen and water to plants and thus crop growth. The effects of biochar are not definitive, and often dependent on both the soil type and the biochar applied. Biochar properties can change according to the feedstock and production parameters, thus for their effective use further investigation is required to link biochar properties to its effects in soil. A high-temperature (600˚ C) biochar from a mixed-hardwood feedstock was investigated. The biochar increased the soil water retention, as demonstrated by a water release curve and field trials. This retention was predominant at higher water potentials, which was attributed to the greater number of meso (storage) pores in the biochar. Biochar did not affect the soil’s saturated hydraulic conductivity; this is thought to be due to the low number of macro (transmission) pores in the biochar. Thus there was no effect on the transmission rate in the soil. Biochar reduced gross ammonium levels in the soil via adsorption, but resulted in increased non-exchangeable ammonium levels, possibly due to physical entrapment. Where carbon was already abundant in the organically managed soil, the adsorbed ammonium reduced nitrification through lower substrate availability. The range of carbon fractions added as a result of the biochar amendment increased the total organic carbon (TOC) content of the soil, but this supplementary carbon was released by the microorganisms as carbon dioxide. Microorganisms in the relatively carbon poor conventionally managed soil (with lower TOC), assimilated the additional labile carbon increasing microbial biomass. The higher microbial biomass, combined with improvements in pH and the higher ammonium levels (as a result of the ammoniacal fertiliser) increased nitrification. These changes in water and nitrogen availability did not alter crop yields as measured in the glasshouse and field trials. The effects of this biochar in a sandy agricultural soil depended on the type and level of carbon and nitrogen present in the soil, thus consideration of these factors should be taken when applying.

For successful restoration of unstable ecosystems in the dumps recreating a fully functioning lan dis needed. Dump substrates often have poor grain composition, extreme pH or are toxic. They also lack important recent organic matter, which improves the overall quality of the soil and is therefore necessary for the development of quality and fertile soil. Therefore, restoration of ecosystems in the dumps is initially very slow. A number of reclamation measures was invented to accelerate this process - for example, heaping up of topsoil to dump substrates. With organic matter present in the topsoil soil formation is faster and often with their physical and chemical properties differ significantly from then developed soils. There has already been number of works written considering development of soils on the Velká podkrušnohorská výsypka so far, none of which, however, did not affect grasslands. The aim of this work was to obtain complete information about the development of chemical and microbial properties of soils that were recultivted by reclaimed topsoil and grassed and then to compare them with developments in the areas of overgrown spontaneous succession. It was found that the total carbon content increases with time only in the reclaimed areas and maximum of the increase is in the depth of...