No-tillage System Research Articles

Alternative Sources of Potassium for Soybean Crops

Over the last three decades, soybean production in the Brazilian agricultural sector has experienced significant yield growth. The soil must have adequate fertility to provide nutrients for good agricultural yield. This study aimed to evaluate the effect of different sources and doses of potassium on the soybean grain yield and its components. The experiment was conducted in the 2022/2023 crop season at the experimental field of the Goiás State University in Ipameri, GO. The experimental design used was randomized blocks arranged in a 3 x 5 factorial scheme, with three potassium sources potassium chloride (KCl: 58% K2O), Phonolite (Ph1:8% K2O and 25% Si), and Hydrothermalized Phonolite (HPh2:12% K2O and 25% Si) and five doses (0, 50, 100, 150, and 200 kg ha-1), with four replications. The management used the no-till system on sorghum straw planting the NEO 750 IPRO soybean cultivar. According to the results, there was an influence of the interaction between the factors only on the number of pods per plant. The potassium doses influenced the first pod insertion height, hectoliter mass, and grain yield. Based on the results, potassium fertilization using the alternative sources, Ph1 and HPh2, reached satisfactory grain yield levels compared to KCl, with the maximum grain yield value, regardless of the source, occurring at a dose of 138.18 kg ha-1 of potassium.

Metagenomic insights into carbon, nitrogen, and phosphorus cycling in a no-till intercropping system

Metagenomic insights into carbon, nitrogen, and phosphorus cycling in a no-till intercropping system

Legacy Effects of Cover Crop on Cash Crop Rhizosphere Microbiota in a No-Till Maize-Soybean Cropping System

Legacy Effects of Cover Crop on Cash Crop Rhizosphere Microbiota in a No-Till Maize-Soybean Cropping System

Machine learning the abiotic stressor impacts on nitrogen availability and photo energy use in dryland forage systems under different tillage and green manuring practices

Background and aimSorghum sudangrass (SSG), a vigorous hybrid C4 plant grown as forage or bioenergy crop during the summer has deeply distributed fibrous root system beneficial to dryland agriculture. Despite these advantages, the crop faces challenges from abiotic stressors, particularly during severe drought seasons. Thus, the goal of planting SSG as a forage is to generate ample biomass with minimal inputs, minimize toxicity, identify stress factors, and implement suitable management strategies with negligible environmental impact. This study focused on machine learning the intricate soil–plant-water-atmosphere relationships associated with abiotic stresses and agroenvironmental variables to enhance energy-efficiency and alleviate nitrogen (N) stress.MethodsA long-term simulation study involving SSG with four N treatments (spring-fallow and N fertilization, and three spring-time cover with 100% residue addition as green manures) under no-till (NT) and conventional (CT) tillage systems was unsuccessful to provide distinct effects of N strategies. Machine learning (ML) was employed to determine how abiotic-stress factors were varied, specifically under influence of green manures such as oat (OG), field peas (FP) and grass peas (GP) under conventional and conservation systems.ResultsResults indicated significantly higher use-efficiency of photosynthetically-active radiation (PAR) and the lowest N stress in NT + FP contrasting with the lowest PAR and the highest N-stress in conventional system. ML Regression models highlighted significant impact of average daily temperatures on water (R2 of 78%) and N-stress (R2 of 79%). Multi-regression ML models, incorporating various agro-environmental variables identified tillage as the most influential factor during wet seasons, water-stress during normal seasons, and temperature as the predominant factor during drought seasons influencing N stress in SSG forage-system.ConclusionConspicuously, drought exhibited a more pronounced influence from green manuring compared to wet or normal seasons in our study. Thus, farmers should be encouraged to adapt the practice of using cover and green-manures despite the concerns about water reserves for summertime cash crops.

Effects of Different Cover Crops and Cotton Planting Rates on Cotton Production in a No-Till System

Single species cover crops and cover crop mixtures, especially legumes, can protect the soil surface and increase soil organic matter in a no-till system. Cotton producers who focus on soil health are interested in maximizing their economic return by minimizing production cost while maintaining yield. Producers can accomplish this by manipulating cotton seeding rates. From 2017 to 2020 field experiments were run in central Alabama to evaluate the effects of cover crop species (cereal rye [Secale cereale L.], crimson clover [Trifolium incarnatum L.], and cereal rye + crimson clover) and cotton seeding rates (54,116, 108,232, and 180,387 seeds ha-1) on no-till cotton production. During the experiments, biomass for cereal rye and crimson clover was similar (5,540 kg ha-1) but was lower compared to their mixture (6,469 kg ha-1). Seed cotton yield in 2018 and 2020 was similar, averaging 4,597 kg ha-1. In 2019 the yield was substantially reduced to 2,068 kg ha-1 due to severe drought. Profit in 2019 was $1,484 ha-1 compared to higher average profit of $6,209 ha-1 in 2018 and 2020. Yield and profitability were greater using the medium or high seeding rate during the 2018 and 2019 seasons. However, under severe drought conditions (2019 season) the low cotton seeding rate was similar in yield and profitability as the medium and high seeding rates. Overall, yield and profits were influenced by cotton seeding rate and weather and not by cover crop type.

Crop rotation effects on the population density of soybean soilborne pathogens under no-till cropping system.

Soilborne diseases are persistent problems in soybean production. Long-term crop rotation can contribute to soilborne disease management. However, the response of soilborne pathogens to crop rotation is inconsistent, and rotation efficacy is highly variable. Selection of proper crop plants and crop sequences for disease management is needed. In this research, the effects of crop rotation on soybean soilborne pathogens were evaluated in a long-term no-till crop rotation field trial in South Dakota. Five rotation treatments were evaluated in this field trial, including corn-soybean (CS; Zea mays L., Glycine max (L.) Merr.), corn-soybean-spring wheat-pea (CSSwP; wheat: Triticum aestivum L., pea: Pisum sativum subsp. arvense (L.) Asch.), corn-soybean-spring wheat-sunflower (CSSwSf; sunflower: Helianthus annus L.), corn-oat-winter wheat-soybean (COWwS; oat: Avena sativa L.), and corn-pea-winter wheat-soybean (CPWwS). Six soilborne pathogens that consistently threaten the United States soybean production were quantified in the field soils using quantitative PCR or egg extraction for soybean cyst nematode. Three soilborne pathogens, Macrophomina phaseolina, Fusarium oxysporum, and Pythium irregulare, were detected, whereas the population density of F. graminearum and F. virguliforme was not measurable in the soil samples. The number of soybean cyst nematode eggs or juveniles was zero or very low in all soil samples. Overall, crop rotation treatments affected the population density of three detected pathogens but varied by crop phase, year, and pathogen species. The population density of three detected pathogens was positively correlated with soil temperature but negatively correlated with soil volumetric water content. Notably, the CPWwS rotation treatment had a consistently lower M. phaseolina population compared with the other rotation treatments, regardless of crop phase and year. This study provided potential crop sequences that limit soilborne pathogen populations in the soil and may reduce disease incidence on the host crops.

The Effects of Potassium Dose, Timing, and Source in Soybean Crops in Brazilian Savannah Oxisol

In Brazil, several silicic rocks can be used as powder-based K sources, which can reduce production costs in agriculture. The optimized supply of K not only increases yield but also contributes to soil fertility preservation and long-term sustainability by curtailing nutrient losses and reducing the risk of nutrient imbalances. Therefore, this study aimed to investigate the effects of K application timing, source, and doses on nodulation, productive components, and productivity of soybeans in a not-tillage system in the Savannah. The experiment was carried out in the field, for two years, in an Oxisol, with a clayey texture. The experimental design was in random blocks, in a 2 × 4 × 3 factorial scheme, as follows: two application timings (early and sowing), four K2O rates (0, 40, 80, and 120 kg ha−1), and three sources (KCl, Potasil, and Ekosil), with four replicates. Potassium fertilizer was broadcasted on the soil without incorporation into the soil. Due to the interactions between doses and K2O sources, there was a linear adjustment for KCl sources, the higher the dose, the lower the nodule mass. Also, for nodule mass, the interaction between dose and application time was significant for the early application of the Ecosil and Potasil sources for 80 kg ha−1. The highest estimated soybean grain productivity was 3262 kg ha−1 with 78 kg ha−1 of K2O, being the most suitable for growing soybeans under a no-tillage system.

Structural quality of a Latosol cultivated with oilseed in succession to soybean

Understanding the changes in soil structure that develop from oilseed crop successions is vital for successful production. The objective of this study was to evaluate the effects of different oleaginous crop successions on the least limiting water range and load-bearing capacity of a clayey Rhodic Hapludox. The following oilseed crops were cultivated under a no-tillage system in autumn-winter: sunflower (Helianthus annuus L.), canola (Brassica napus L. and Brassica rapa), safflower (Carthamus tinctorius L.), crambe (Crambe abyssinica Hochst.) and niger seed (Guizotia abyssinica). They were sown after soybean and soybean/corn (summer/fall-winter). When the autumn-winter crops flowered, soil samples with structure intact were collected at the 0.0–0.5 m and 0.5–0.10 m depths in metal cylinders. It was observed that in terms of water interval, the poorest soil structural quality in the 0.0–0.5 m layer was provided by the corn/safflower and corn/crambe successions. In terms of soil water content, the optimal time for soil management practices varied for the different oilseeds succeeding soybean. Soil load capacity varies inversely with water content and directly with soil density. Niger grown during autumn-winter in succession to soybean improved Rhodic Hapludox structure more than the other crop successions.

Resiliência de plantas de cobertura à seca

Straw production from cover crops and the sustainability of no-tillage farming systems can be compromised by low rainfall during the dry off-season in Central Brazil. This study investigated the drought resilience of five cover crop species under drought stress conditions. Three irrigation levels [100% pot capacity – CV (well-watered conditions), 60% CV (moderate drought stress) and 25% CV (severe drought stress)] and five grass cover crop species [Urochloa brizantha cv. BRS Piatã, U. brizantha cv. Marandu, U. brizantha cv. Xaraés, U. ruziziensis cv. Comum and Pennisetum glaucum cv. ADR 300] were tested using a randomized block design with a 3 × 5 factorial arrangement and three replications. Canonical variable analysis (CVA) and a correlation network were established with the variables evaluated. The CVA showed that 88.6% of the total variation of the data was retained in the first two canonical variables. The plants were exposed to water stress for 25 days during the tillering and stem elongation phases. Plants of the genus Urochloa (U. ruziziensis, U. brizantha cv. Marandu, and U. brizantha cv. Xaraés) showed higher total dry matter production under normal irrigation conditions. However, under moderate water stress conditions, U. ruziziensis was the cover crop with greater resilience, since these conditions culminated in higher dry matter production.

INFLUENCE OF TILLAGE SYSTEMS ON SELECTED SOIL CHARACTERISTICS AND YIELD OF SPRING CEREALS

Climate change necessitates a revised approach to crop cultivation technologies, prioritizing enhanced agricultural practices for soil conservation, water retention, and high-quality yields. To evaluate the influence of different soil tillage systems on yield and yield quality in spring cereals, a field experiment was conducted at the Agricultural Research and Development Station (ARDS) Turda. The experiment followed a split-plot design with two replications, within a 3-year rotation (soybean–spring cereals–maize). Three spring cereal species (wheat, two oat varieties, and barley) were tested under four tillage systems (plowing, chiseling, disking, and direct sowing) on Phaeozem soil with a clay-clay texture. The hectoliter weight (TW), thousand kernel weight (TKW), and grain protein content are influenced to some degree by the tillage system. The highest soil compaction levels were observed in the NT system, while the lowest were recorded in the CS system. High temperatures and drought led to notable soil moisture decreases in June and July, especially in the minimum tillage with disking (MTD) and NT systems. Tillage with plow and chisel resulted in lower bulk density values. Yields in the unconventional systems (minimum tillage with chisel (MTC) and MTD) were comparable to those in the conventional system (CS), indicating their viability as alternatives to traditional plowing. A yield reduction was noted in the no-tillage system.

Integrating insect dynamics in agricultural ecosystems: the role of predators, prey, and sustainable practices in enhancing biodiversity and ecosystem resilience

Abstract Insects play a pivotal role in food webs, influencing ecosystem stability through their interactions as herbivores, predators, and prey. This review explores the impact of agricultural practices on insect dynamics, focusing on how no-till farming, mulching, crop residues, and diverse farming systems like intercropping and crop rotation can shape predator-prey interactions. No-till systems, by reducing soil disturbance, enhance the survival of natural enemies such as ants, spiders, and beetles, indirectly regulating pest populations. Practices like mulching and maintaining crop residues hinder pests’ ability to locate host plants, boosting the abundance of natural predators. Additionally, crop rotation and intercropping create varied habitats, supporting a higher diversity of predators and improving biological pest control. These integrated approaches not only reduce reliance on chemical pesticides but also foster ecological balance and enhance agricultural sustainability. The review highlights the importance of sustainable land-use practices in preserving insect biodiversity and improving ecosystem resilience. Keywords: Biodiversity, food web and predator-prey interactions.

Wheat productivity and nitrogen use efficiency in no-till systems: a comparative analysis of crop-pasture and continuous cropping rotations in Uruguay

IntroductionUruguayan agriculture’s transition to no-till farming and intensified practices, replacing crop-pasture (CP) systems with continuous cropping (CC) rotations, has disrupted biological nitrogen fixation (BNF). Despite this, diversified cropping sequences, including C4 species, have maintained the soil organic carbon (SOC) balance under no-till management, with limited overall impacts on productivity and sustainability. The effects of these changes on wheat productivity and nitrogen use efficiency (NUE) need to be further investigated.MethodsThis study, conducted within a long-term experiment (LTE) under rainfed conditions, compared wheat productivity in CP and CC rotations. Wheat following CP and CC were analyzed over three seasons. Variables measured included soil nitrogen (N) concentration, wheat grain yield (WGY), grain protein concentration (GPC), and NUE. Four N fertilizer levels were applied to each rotation system to assess their impact.ResultsCC rotation consistently outperformed CP in WGY, with 2425 and 1668 kg ha−1 averages, respectively. CP showed slightly higher GPC (10.92%) than CC (10.48%). Nitrate-N levels at tillering positively correlated with WGY and negatively with GPC, but the relationship differed by rotation. Soil NUE indices were higher in CC rotations.DiscussionThe study’s findings highlighted the potential of CC rotation, especially when including C4 species in the crop sequence, to achieve higher wheat productivity in the short term due to healthier soil conditions compared to wheat seeded after post-pasture in CP. Additionally, our study highlights that the effect of the previous crop on yield and NUE in wheat was more relevant than the expected residual effect of the pasture phase in CP, primarily due to the quality of residues and the temporary adverse effects of soil compaction caused by livestock trampling.

Field Application of Mycorrhizal Inoculant Influences Growth, Nutrition, and Physiological Parameters of Corn Plants and Affects Soil Microbiological Attributes

Mycorrhizal inoculants can contribute to the development of corn crops by improving crop productivity. In this sense, the objective of this study was to evaluate the effects of a mycorrhizal inoculant on the dynamics of root system growth, gas exchange, corn crop productivity, and microbial activity in the rhizospheric soil in a no-till area with different levels of available soil phosphorus. The experiment was conducted during the 2019/2020 and 2020/2021 growing seasons. At 75 days after plant emergence, root morphological parameters (total root length (cm), average root diameter (mm), root surface area (cm2), and root volume), shoot biomass production, P content in the plant shoots, gas exchange, and microbiological attributes of the rhizospheric soil of corn were evaluated. At the end of the cycle, corn grain yield was determined. A beneficial effect of AMF inoculation was observed on the root and shoot parameters regardless of soil P level. Under conditions of evenly distributed rainfall during the experiment (2019/2020 season), AMF inoculation contributed to a 90% increase in acid phosphatase activity and a 76% increase in microbial biomass carbon (C-BIO), independent of soil P level. In contrast, under water deficit conditions (2020/2021 season), AMF inoculation provided a 29% increase in grain yield. We concluded that introducing a commercial mycorrhizal inoculant in corn benefits root system morphological parameters and physiological traits, and favors the activity of enzymes related to increased P availability, contributing to increased crop productivity in a no-till system.

Spatial variability analysis of physical attributes of subsurface soil in an area of no-till system with crop rotation

Spatial variability analysis of physical attributes of subsurface soil in an area of no-till system with crop rotation

Hairy vetch influence on nitrous oxide and nitrate leaching losses during corn growing seasons in reduced and no-till systems

Shifting from reduced tillage (RT) to no-till (NT) often reduces phosphorus (P) runoff by minimizing soil erosion. However, it might increase nitrous oxide (N2O) emissions or nitrate-N (NO3-N) leaching. Including a legume cover crop such as hairy vetch (Vicia villosa L.) before corn (Zea mays L.) is a common practice among growers in the Midwest USA. However, the effects of hairy vetch following soybean (Glycine max L.) harvest on NO3-N leaching and N2O emissions during the following corn season in soil with clay and fragipans are less assessed. This study evaluated the influence of cover crop (hairy vetch vs. no-CC control) and tillage systems (NT vs. RT) when 179 kg ha−1 nitrogen (N) was applied at planting on (i) corn yield, N uptake, removal, and balance; (ii) N2O emissions and NO3-N leaching; (iii) yield-scaled N2O emissions and NO3-N leaching during two corn growing seasons. We also evaluated factors influencing N2O emissions and NO3-N leaching via principal component analysis. Corn grain yield was higher in RT (8.4 Mg ha−1) than NT (6.2 Mg ha−1), reflectingmore available N in the soil in RT than NT, possibly due to the favorable aeration and increased soil temperature in deeper soil layers resulting from tillage. Hairy vetch increased corn grain yield and soil N. However, it led to higher losses of both N2O-N and NO3-N, indicating that increased corn grain yield, due to the hairy vetch’s N contribution, also resulted in higher N losses. Yield-scaled N2O-N emissions in NT-2019 (3696.4 g N2O-N Mg−1) were twofold higher than RT-2019 (1872.7 g N2O-N Mg−1) and almost fourfold higher than NT-2021 and RT-2021 indicating in a wet year like 2019, yield-scaled N2O-N emissions were higher in NT than RT. Principal component analysis indicated that NO3-N leaching was most correlated with soil N availability and corn grain yield (both positive correlations). In contrast, due to the continued presence of soil N, soil N2O-N fluxes were more driven by soil volumetric water content (VWC) with a positive correlation. We conclude that in soils with claypan and fragipans in humid climates, NT is not an effective strategy to decrease N2O-N fluxes. Hairy vetch benefits corn grain yield and supplements N but increases N loss through NO3-N leaching and N2O-N emissions.

Use of Soil Remineralizer to Replace Conventional Fertilizers: Effects on Soil Fertility, Enzymatic Parameters, and Soybean and Sorghum Productivity

The reliance on soil acidity correctives and mineral fertilizers poses a threat to food production due to the finite nature of these resources and their susceptibility to price volatility from importation. Soil remineralizers have emerged as a sustainable alternative. This study assessed silicate agrominerals as soil remineralizers to replace limestone, gypsum, and conventional fertilizers in a no-tillage system. Conducted in a tropical climate on sandy/medium-textured Ultisol, twelve treatments (combinations of liming, gypsum, mineral fertilization, and remineralizer) were tested for their effects on soybean and sorghum agronomic traits. Applying a remineralizer at 2500 kg ha−1 enhanced soybean productivity by 15% and sorghum by 35% in succession, along with increases in P, S, Ca, Mg, sum of bases (SB), cation exchange capacity (CEC), base saturation (V%) in the 0–0.20 m layer and organic matter in the 0–0.40 m layer, benefiting soil microbiological parameters, with the treatment combining all four products improving soil fertility; however, for better crop productivity, split applications appear to be an alternative to avoid nutrient imbalance. Due to the finer particle size of the remineralizer, which allows faster nutrient release, further research is recommended to investigate the long-term impacts on soil microbiota dynamics, optimal doses and combinations, and economic viability across various soil types and climates.

Performance of Urea-Based Enhanced Efficiency Fertilizers Under Sidedress Nitrogen Placement Methods

Enhanced efficiency nitrogen fertilizer (EENF) is a viable N management tool that can minimize N loss and maximize crop productivity. Research on the efficiency of EENF under relatively newer N-sidedress placement methods for liquid fertilizers, such as Y-Drop dribble, is limited, hence the necessity to address this knowledge gap. A two-year field trial was conducted to evaluate ammonia volatilization, grain quality, and grain yield from surface-applied EENF forms of urea and EENF forms of urea ammonium nitrate (UAN) applied under four placement methods in a rainfed no-till corn production system. The EENF forms of urea evaluated in this trial included Environmentally Smart Nitrogen, SuperU, and ANVOL-treated urea, while ANVOL-treated UAN was the EENF form of UAN. All the urea fertilizers were surface broadcasted while the UAN fertilizers were broadcasted, dribbled in between rows, Y-Drop dribbled, and injected behind colters. Among the non-EENF, urea volatilized the most ammonia (23.1% of total N applied) compared to UAN. Broadcast UAN was much more susceptible to ammonia volatilization than dribbled UAN in between rows. In this trial, the EENF forms of urea and UAN reduced ammonia loss by 65 to 94 and 50 to 51%, respectively, compared to their corresponding non-EENF forms. In 2021, the grain yield of the non-EENF forms of UAN was similar to the EENF forms of the corresponding placement methods. In contrast, there was an additive yield effect from all the urea forms of EENF. A significant negative relationship was observed between ammonia loss and grain protein, grain N, and grain yield; hence, placement methods with higher ammonia loss potential are prone to yield loss.

Cover crops influence the physical hydric quality of a tropical sandy soil under no-tillage cotton cropping

ABSTRACT Reduced stability and structural resilience expose sandy soils to physical degradation under intensive production systems. This study aimed to evaluate the influence of different cover crops (CC) under no-tillage system (NTS) cotton cropping, grown either individually or in combination, on the soil physical quality (SPQ) of a sandy loam Oxisol (Latossolo) in southeastern Brazil. To quantify the effects of CC on soil physical quality indicators, an experiment in randomized blocks design was implemented with the treatments: CC1: single cultivation of Ruzi grass; CC2: Intercropping of Pearl Millet + Ruzigrass; CC3: Intercropping of Pearl Millet + Velvet bean; CC Mixture : Intercropping of Ruzi grass, Pearl Millet and Velvet bean; and Control: maintenance of spontaneous plants. Undisturbed samples were taken from layers 0.00-0.10, 0.10-0.20, 0.20-0.40 and 0.40-0.60 m, in which were determined the soil bulk density (Bd), total porosity (TP), available water (AW), soil penetration resistance (PR) and the least limiting water range (LLWR). According to the multivariate analyses, the CC 2 treatment resulted in better SPQ compared to the other treatments. The LLWR, air-filled porosity (θ AFP ), and AW were responsible for differentiating the CC 2 treatment compared to the other treatments evaluated. Regardless of treatments, values of Bd> 1.75 Mg m -3 result in loss of SPQ due to the significant increase in PR and decreases in AW and LLWR. In the CC 3 and Control, there was a physical impediment caused by the increase in Bd in the 0.10-0.20 m layer, which could result in the confinement of cotton roots to the surface, making them more susceptible to water stress. Soil PR reached values greater than 2.5 MPa for water contents lower than the θ PWP in most treatments. In treatment CC3, for water contents equivalent to the θ PWP , the PR did not exceed 6 MPa, while for the other treatments, the PR reached values greater than 10 MPa. Only the PR was influenced using CC. Soil moisture is considered crucial to maintain PR below impeding values, determining the control of the physical quality of this sandy soil.

The Crop Succession Systems Under No-Tillage Alters the Surface Layer Soil Carbon Stock and Stability

The main challenge of the no-tillage system (NTS) is to reconcile productivity, the maintenance of surface residues, and the stabilization of soil organic matter (SOM). To address this challenge, particularly in tropical regions, various cover crops have been tested. The objective of this study was to test the effects of agricultural crop succession systems on the stock and stability of soil organic carbon in different surface layers of the soils. The research was carried out in the state of Goiás, Brazil, in an experiment set up in 2016, designed in randomized blocks with a split-plot scheme (treatments and soil layers), comprising four repetitions (blocks). The treatments (plots) consisted of crops grown in succession to soybean, which were as follows: T1—soybean/corn (Zea mays); T2—soybean/pearl millet (Pennisetum glaucum); T3—soybean/Urochloa ruziziensis (brachiaria); and T4—corn + Urochloa ruziziensis. The subplots represented the following soil layers: 0–5, 5–10, 10–20, and 20–40 cm. We evaluated the biomass dry mass and the soil parameters such as soil density, total porosity, and light organic matter across all layers. The organic carbon, grain size fractionation (mineral-associated organic carbon—MOC; sand-sized carbon—POC), and isotopic composition (δ13C) were determined in the 0–5 and 5–10 cm layers. The highest biomass dry production was observed in the soybean/pearl millet succession, which reduced the soil density and increased the total porosity in the surface layer. The soybean/pearl millet treatment produced high amounts of light organic matter, particularly in the 0–5 cm layer, a result also found for the soybean/brachiaria and soybean/corn + brachiaria systems. The crop successions did not alter the soil carbon stock or stability; however, the surface layer stored the highest amount of carbon, with elevated total organic carbon values and carbon stocks and stability (MOC and POC). Overall, in this study, replacing corn with other crops in succession with soybean did not affect the stock or stability of soil organic carbon. The species grown in succession with soybean contributed to the higher surface carbon stock and stability, promoting the formation of more stable and recalcitrant carbon.

Long-Term Effects of Nitrogen Sources on Yields, Nitrogen Use Efficiencies, and Soil of Tilled and Irrigated Corn

Although corn is the most important and nitrogen (N)-fertilized crop, there is a lack of long-term data on the effects of organic and inorganic N fertilizers on the N balance and losses for corn systems under different tillage approaches. From 2012 to 2023, we assessed the effects of the N source on the grain yields from cultivated continuous corn receiving irrigation at a site with minimal erosion in Fort Collins, Colorado, USA, and compared these effects to no-till (NT) and strip till (ST) systems receiving inorganic N. An N balance accounting for N and carbon (C) sequestration found a system nitrogen use efficiency (NUESys) for organic N fertilizer (manure) with a tillage of 86.6%, which was higher than the NUESys of 62.6% with inorganic N fertilizer (enhanced efficiency fertilizer, EEF). Conventional tillage with manure use is a good management practice that contributed to higher grain yields (2 of 11 years), C sequestration (p < 0.05), soil organic N content (p < 0.05), and soil phosphorus (P) content than inorganic N fertilizer with tillage (p < 0.05). The tilled systems, whether receiving organic or inorganic N fertilizer, had higher yields and grain N content than the NT and ST systems receiving inorganic N fertilizer (p < 0.05). The grain production of the cultivated system receiving organic N fertilizer did not decrease with time, while the yields of the cultivated system receiving inorganic N fertilizer decreased with time (p < 0.05), suggesting that cultivated systems receiving organic N fertilizer may be more sustainable and better able to adapt to a changing climate. Additionally, a combination of manure (30% of N input) with EEF (70% of N input) contributed to a synergistic effect that increased the agronomic productivity (harvested grain yields).