Crop Biomass Production Research Articles

Mapping predicted biomass in cereal rye using 3D imaging and geostatistics

Abstract Cover crops are becoming an increasingly important tool for weed suppression. Biomass production in cover crops is one of the most important predictors of weed suppressive ability. A significant challenge for growers is that cover crop growth can be patchy within fields, making biomass estimation difficult. This study tested ground-based structure-from-motion (SfM) for estimating and mapping cereal rye (Secale cereale L.) biomass. SfM generated 3D point clouds from red, green, and blue (RGB) videos collected by a handheld GoPro camera over five fields in North Carolina during the 2022 to 2023 winter season. A model for predicting biomass was generated by relating measured biomass at termination using a density–height index (DH) from point cloud pixel density multiplied by crop height. Overall biomass ranged from 320 to 9,200 kg ha−1, and crop height ranged from 10 to 120 cm. Measured biomass at termination was linearly related to DH (r2 = 0.813) through levels of 9,000 kg ha−1. Based on independent data validation, predicted biomass and measured biomass were linearly related (r2 = 0.713). In the field maps generated by kriging, measured biomass data were autocorrelated at a range of 5.4 to 42.2 m, and predicted biomass data were autocorrelated at a range of 3.4 to 12.0 m. However, the spatial arrangement of high- and low-performing areas was similar for predicted and measured biomass, particularly in fields with greatest patchiness and spatial correlation in biomass values. This study provides proof-of-concept that ground-based SfM can potentially be used to nondestructively estimate and map cover crop biomass production and identify low-performing areas at higher risk for weed pressure and escapes.

Engineered nanomaterials reduce metal(loid) accumulation and enhance staple food production for sustainable agriculture.

Metal(loid) contaminants in food pose a global health concern. This study offers a global analysis of the impact of nanomaterials (NMs) on crop responses to metal(loid) stresses. Our findings reveal that NMs have a positive effect on the biomass production of staple crops (22.8%), while showing inhibitory effects on metal(loid) accumulation in plants (-38.3%) and oxidative damage (-21.6%) under metal(loid) stress conditions. These effects are influenced by various factors such as NM dose, exposure duration, size and composition. Here we introduce a method using interval-valued intuitionistic fuzzy values by integrating the technique for order preference by similarity to an ideal solution and entropy weights to compare the effectiveness of different NM application patterns. These results offer practical insights for the application of NMs in similar multi-criteria decision-making scenarios, contributing to sustainable agriculture and global food safety.

Controlled drought stress affects rosemary essential oil composition with minimal impact on biomass yield

Rosemary (Salvia rosmarinus Spenn.), an indigenous medicinal and aromatic plant within the Mediterranean region, yields essential oils renowned for their antimicrobial, antioxidant, anticancer, and anti-inflammatory properties. When subjected to various stress conditions, rosemary intensifies the production of essential oils as a defensive mechanism, as occurs when it is subjected to drought stress, making it a potentially interesting crop for marginal dryland areas of Sicily and other Mediterranean areas. Managing rosemary cultivation through controlled drought stress close to the balsamic period may increase the concentration and quality of essential oils and optimize the use of limited resources like water. We conducted two on-farm field experiments in Sicily, southern Italy, to assess the effect of controlled drought stress on rosemary biomass, essential oil yield, and composition. The hypothesis was that drought could improve the concentration of essential oils and modify their chemical composition by increasing valuable aromatic components without negatively impacting crop biomass production, increasing interest in cultivating this species. The experiments were co-designed with farmers selecting dedicated field experiments, cultivars, and crop management. Drought stress was applied during autumn and spring in correspondence with medium-high temperatures and rainwater scarcity. The irrigation input was reduced for three weeks during the balsamic period for each trail. Under stressed conditions, morphometric traits were measured. At harvest time, essential oils were extracted using microwave-assisted extraction. Under the same farm conditions, the canopy height was significantly higher in ‘Barbeque’ than ‘Tuscan Blue cv. (67.3 cm vs. 43.8 cm) This indicates a genotype influence on stress response. Essential oil yield increased by 30 % in plants of Tuscan blue cv. subjected to stress conditions in one of two farms. Additionally, drought stress altered the aromatic profile of the essential oil, resulting in differing percentages of key compounds between stressed and unstressed plants. Generally, there was a higher α-pinene percentage in unstressed plants and higher bornyl-acetate and β-caryophyllene concentrations in drought-stressed plants. In the Scicli farm, α-pinene decreased in response to water stress, while camphene and myrcene increased. Our results summarized that controlled drought stress had a minimal impact on rosemary growth, increasing the percentages of some terpenes in its essential oils. No severe decrease was observed in the synthesis of essential oils, suggesting that rosemary is suitable for marginal soils in many Mediterranean countries to protect soils and diversify crops in farms.

Cover Crop Species Selection, Seeding Rate, and Termination Timing Impacts on Semi-Arid Cotton Production

By improving soil properties, cover crops can reduce wind erosion and sand damage to emerging cotton (Gossypium hirsutum L.) plants. However, on the Texas High Plains, questions regarding cover crop water use and management factors that affect cotton lint yield are common and limit conservation adoption by regional producers. Studies were conducted near Lamesa, TX, USA, in 2017–2020 to evaluate cover crop species selection, seeding rate, and termination timing on cover crop biomass production and cotton yield in conventional and no-tillage systems. The no-till systems included two cover crop species, rye (Secale cereale L.) and wheat (Triticum aestivum L.) and were compared to a conventional tillage system. The cover crops were planted at two seeding rates, 34 and 68 kg ha−1, and each plot was split into two termination timings: optimum, six to eight weeks prior to the planting of cotton, and late, which was two weeks after the optimum termination. Herbage mass was greater in the rye than the wheat cover crop in three of the four years tested, while the 68 kg ha−1 seeding rate was greater than the low seeding rate in only one of four years for both rye and wheat. The later termination timing produced more herbage mass than the optimum in all four years. Treatments did not affect cotton plant populations and had a variable effect on yield. In general, cover crop biomass production did not reduce lint production compared to the conventional system.

Thermal time and precipitation dictate cereal rye shoot biomass production

ContextMaximizing cover crop biomass production is key to agroecosystem service delivery. Cover crop biomass accumulation is particularly important in corn (Zea mays L.) silage cropping systems due to the high rate of crop biomass removal that leaves the soil surface mostly bare from early fall until planting the following spring. ObjectiveWe evaluated how weather factors affect rye (Secale cereale L.) cover crop shoot biomass in different rotations including corn silage and soybean [Glycine max (L.) Merr.] and their influence on soybean and corn silage yields. MethodsIn a 13-year field study in a corn silage-soybean rotation, we assessed rye biomass and main crop yields when rye was planted after one or both main crops every year. ResultsRye after silage produced 1.98 Mg ha−1 more shoot biomass than rye after soybean. Thermal time (expressed as growing degree days) had a greater impact than precipitation on the shoot biomass of rye cover crop. A threshold of 800 growing degree days (0°C base) in the fall was determined, above which final biomass was not limited by fall thermal time (R2=0.58). Rye biomass was most strongly affected by fall thermal time (below 800 growing degree days) after soybean and by spring growing degree days and precipitation after corn silage. Rye cover crop inclusion did not decrease corn silage and soybean yields in 12 out of 13 years. ConclusionFall growing degree days below a threshold may limit the maximum potential for spring rye cover crop growth, but spring growing degree days or precipitation may prevent maximum growth from occurring when exceeding 800 growing degree days. Planting rye cover crops in both phases of the rotation did not affect cover crop biomass or main crop yields and may hold a greater potential to protect the soil than planting after only one crop in the rotation. ImplicationsCropping systems that allow a rye cover crop to be planted early enough to accumulate 800 growing degree days in the fall have the best potential for high cover crop biomass production.

Implementation of the AquaCrop Model for Forecasting the Effects of Climate Change on Water Consumption and Potato Yield Under Various Irrigation Techniques

In this study, the AquaCrop model was employed to analyze the impact of projected future climate changes on the water usage and biomass production of potato crops in Babylon, Iraq, under varying irrigation methods. The irrigation techniques evaluated included sprinkler irrigation, surface drip irrigation, and subsurface drip irrigation at depths of 10 cm and 20 cm. The study involved simulating and forecasting conditions for the year 2050, comparing them to current conditions. The model measured and predicted the evapotranspiration (ETa) and actual biomass of potato crops for 2050 using the RCP 8.5 scenarios, which outline different trajectories for greenhouse gas emissions. The AquaCrop model was calibrated and validated using statistical measures such as the R2, RMSE, CV, EF, and D, achieving a 99% accuracy level in its performance. The findings suggest that using drip irrigation systems and applying the AquaCrop model significantly mitigates the adverse effects of environmental stress on desert soils and enhances sustainable agricultural practices in arid regions.

Plant Biostimulants Enhance Tomato Resilience to Salinity Stress: Insights from Two Greek Landraces

Salinity, one of the major abiotic stresses in plants, significantly hampers germination, photosynthesis, biomass production, nutrient balance, and yield of staple crops. To mitigate the impact of such stress without compromising yield and quality, sustainable agronomic practices are required. Among these practices, seaweed extracts (SWEs) and microbial biostimulants (PGRBs) have emerged as important categories of plant biostimulants (PBs). This research aimed at elucidating the effects on growth, yield, quality, and nutrient status of two Greek tomato landraces (‘Tomataki’ and ‘Thessaloniki’) following treatments with the Ascophyllum nodosum seaweed extract ‘Algastar’ and the PGPB ‘Nitrostim’ formulation. Plants were subjected to bi-weekly applications of biostimulants and supplied with two nutrient solutions: 0.5 mM (control) and 30 mM NaCl. The results revealed that the different mode(s) of action of the two PBs impacted the tolerance of the different landraces, since ‘Tomataki’ was benefited only from the SWE application while ‘Thessaloniki’ showed significant increase in fruit numbers and average fruit weight with the application of both PBs at 0.5 and 30 mM NaCl in the root zone. In conclusion, the stress induced by salinity can be mitigated by increasing tomato tolerance through the application of PBs, a sustainable tool for productivity enhancement, which aligns well with the strategy of the European Green Deal.

Summer cover crop and temporary legume-cereal intercrop effects on soil microbial indicators, soil water and cash crop yields in a semi-arid environment

ContextFew studies have investigated summer cover crops as a replacement for bare fallow in semi-arid temperate regions, and summer cover crop impacts on soil biological function, water balances and subsequent winter crop yields in these regions remain largely unknown. ObjectiveThe 4-year field study aimed to determine the consequences of replacing a summer fallow with a summer growing cover crop on soil function, water balances and subsequent winter cash crop yields in a semi-arid region (486 mm mean annual rainfall) of the Australian southern cropping zone. MethodsA canola (Brassica napus)-wheat (Triticum aestivum L.) rotation with summer fallow was compared to the same rotation with either i) a single species (buckwheat, Fagopyrum esculentum L.) summer cover crop; ii) a four-species mixed brassica + cereal summer cover crop or iii) a cropping sequence with a temporary legume intercrop in the wheat phase of the rotation. Cover crop biomass production, soil water to a depth of 90 cm at cash crop sowing, crop yields and soil functional indices were quantified. ResultsCover crops produced 500–700 kg biomass ha−1 in the 2020 and 2021 seasons and 1000–2400 kg biomass ha−1 in 2022. The four-species mixed cover crop significantly lowered soil water (around 30 mm; P < 0.05) at the time of sowing the cash crop compared to the control and resulted in 15% reduction (P = 0.12) in canola seed yield in 2020, but no significant effect of cover crops of soil water and mineral N at sowing, or cash crop yields, were observed in subsequent seasons. In 2021 the temporary vetch intercrop produced > 1000 kg ha−1 biomass over 9 weeks, and led to a (non-significant) 10% wheat yield reduction. There was no significant effect of cover crop or temporary intercrop treatments on soil functions in the 2020 or 2021 seasons, but activities of several soil enzymes (leucine aminopeptidase, arylsulfatase and B-glucosidase; P < 0.05) and water-soluble carbon (P = 0.059) were significantly higher in the summer cover crop plots compared to control and intercrop plots in March 2022 following termination of the cover crops. These changes coincided with a significant increase in saturated hydraulic conductivity in the four-species cover crop plots in March 2022 compared to control plots. ImplicationsThe study did not provide any compelling evidence for benefits of summer cover crops over fallow in the short term (3–4 years). The relatively low cover crop biomass production over the 4-year study suggests summer cover crops are unlikely to substantially improve soil carbon levels in temperate, semi-arid cropping systems.

Detection of Hybrids in Willows (Salix, Salicaceae) Using Genome-Wide DArTseq Markers.

The genus Salix, comprising some 400-500 species, is important in various alluvial or wet habitats of the northern hemisphere. It is a promising crop for applications such as biomass production, biofuels, or environmental projects. Clear species delimitation is crucial in ecology, biotechnology, and horticulture. DArTseq markers, a genome-wide technique, were tested for species and hybrid identification. A total of 179 willow samples were analysed, including six species of Salix subgen. Salix and four species of Salix subgen. Vetrix, including those used in biomass crop production, representing important European taxa. Identification of species-specific markers, clustering analyses (principal coordinate analysis, neighbor-joining) and Bayesian methods (Structure) unambiguously identified putative hybrids. In addition to demonstrating the high efficiency of DArT-seq markers in identifying willow hybrids, we also opened-up new questions about hybridisation processes and systematics. We detected unidirectional hybridisation between S. alba and S. fragilis, forming backcross hybrids, and we rejected the hypothesis that S. fragilis does not occur naturally in Europe. Further, the isolated position of Salix triandra within the genus was confirmed.

Light partitioning strategies impact relative fitness of weeds and cover crops when drill-interseeding in corn

AbstractDrill-interseeding cover crops into corn (Zea mays L.) is an emerging establishment method in northern U.S. production regions. However, cover crop performance in interseeded systems remains variable, and creating environments that are conducive to cover crop but not weed growth is challenging. Cultural practices that partition resources between corn and interseeded cover crops have potential to improve performance if weeds are adequately managed. This study evaluated interactions among corn hybrids differing in leaf architecture (upright, pendulum), corn row spacing (76 cm, 152 cm), and interseeding timing (V3, V6) on light transmittance, relative fitness of cover crop species (cereal rye [Secale cereale L.], annual ryegrass (Lolium multiflorum Lam), red clover [Trifolium pratense L.]) and weeds, and corn grain yield at three U.S. Northeast locations. Results showed that light transmittance through the corn canopy was greater in 152-cm row spacing compared with 76-cm row spacing at the V6 growth stage, with the magnitude of difference increasing at the V10 corn growth stage. Corn hybrids had a marginal effect on light transmittance. The effect of row spacing and interseeding timing on fall cover crop biomass varied across cover crop species and locations. In 76-cm rows, interseeding earlier (V3) increased cover crop biomass production. The relative fitness of cover crops was greater than that of weeds in each combination of cultural practices that included narrow spacing (76 cm), whereas the relative fitness of weeds was greater than that of cover crops when interseeding in wide rows (152 cm). The effect of row spacing on corn yield varied among locations, with higher yields observed in 76-cm row spacing compared with 152-cm at two of three locations. Our results show that interseeding early (V3) on 76-cm row spacing can balance cover crop and corn production management goals, while placing cover crops at a relative fitness advantage over weeds.

Traditional soil fertility management ameliorates climate change impacts on traditional Andean crops within smallholder farming systems

Global changes, particularly rising temperatures, threaten food security in smallholder mountain communities by impacting the suitability of cultivation areas for many crops. Land-use intensification, associated with agrochemical use and tillage, threatens soil health and overall agroecosystem resilience. In the Andean region, farmers often cultivate crops at multiple elevations. Warming climates have led to a shift in cultivation upslope, but this is not feasible in many areas. Traditional soil fertility management practices together with a focus on traditional (orphan) crops offers promise to cope with rapid climate warming in the region. To understand the impacts of warming and changing nutrient management, we established two side-by-side experiments using the traditional Andean crops Oxalis tuberosa (Oca) and Lupinus mutabilis (Tarwi) at three elevations, each with two fertility treatments (organic and synthetic). Soil and climate data (i.e., temperature and precipitation) were collected throughout the growing season, and crop performance was evaluated through impacts on yield and other growth metrics (e.g., biomass, pest incidence). We used two-way ANOVA to assess the influence of site (elevation) and management type (organic vs. synthetic) on crop performance. Results indicated that warmer climates (i.e., lowest elevation) negatively impact the production and performance of O. tuberosa, but that organic fertilization (sheep manure) can help maintain crop yield and biomass production in warmer conditions relatively to synthetic nutrient inputs. In contrast, L. mutabilis showed accelerated growth in warmer conditions, but grain yield and biomass production were not significantly affected by site and showed no interaction with nutrient management. Our findings highlight that climate warming represents a serious threat to small-scale crop production in the Peruvian Andes and could cause severe declines in the production of locally important crops. Additionally, the continued reliance on traditional crops with organic inputs, instead of synthetic fertilizers, may help support agricultural productivity and resilience under climate change.

Residual herbicides in corn and their effect on fall‐planted cover crop species

AbstractThe use of residual herbicides as a part of preemergence (PRE) and in‐season layered treatments has proven to be an effective strategy for controlling late‐emerging broadleaf weed species in annual crops. However, the use of residual PRE herbicides has the potential to negatively affect other crops within an annual two‐crop rotation, such as fall‐planted cover crops. The intent of this study was to determine if PRE herbicides commonly used in the upper Midwest United States would affect stand density, height, and biomass production of fall‐planted cover crops. Field studies were conducted at three locations that differed in soil type and climate. Four PRE herbicides were applied in silage corn (Zea mays L.) in the spring: dimethenamid‐P (single application), dimethenamid‐P + saflufenacil, acetochlor + clopyralid + mesotrione, and a layered treatment of dimethenamid‐P at planting and 30 days after first application. Three cover crops were planted in the fall following silage corn harvest with a no‐till drill: winter cereal rye (Secale cereale L.), winter camelina (Camelina sativa L.), and red clover (Trifolium pratense L.). Although some of the PRE HBs tested affected cover crop spring plant density and height in sandy soils, there was no difference in cover crop biomass production at termination between herbicide treatments, regardless of soil type. These results indicate that the application of these residual PRE herbicides for control of late‐emerging weed species did not interfere with cover crop biomass production as long as soil moisture was not limiting.

Short-term effects of subsoil management by strip-wise loosening and incorporation of organic material

Agricultural production in Central Europe increasingly suffers from extreme drought events. Improving root access to nutrient and water resources in the subsoil below the plow layer is a potential option to maintain productivity during dry summers. Here, we tested a strip-wise subsoil amelioration method that combines subsoil loosening with organic matter incorporation into the subsoil (biowaste or green waste compost) and compared it with a treatment of only subsoil loosening and a non-ameliorated control. A field experiment with randomized block design was conducted on a Luvisol with an argic horizon (Bt), with a rotation of spring barley and winter wheat. In the first two years after amelioration, we monitored soil physico-chemical parameters, microbial biomass, and shoot and root growth at anthesis as well as harvested grain yield and quality. Subsoil loosening with organic matter incorporation significantly decreased soil bulk density at the depth of compost incorporation when biowaste compost was used, but not when green waste compost had been incorporated. Nutrient stocks, nutrient availability and microbial biomass were not consistently affected by the subsoil amelioration. Nevertheless, the incorporation of organic material, especially biowaste compost, significantly increased root growth into the subsoil and subsequently significantly enhanced crop nutrient uptake, biomass and grain yield production. Green waste compost incorporation had less pronounced effects, with an increase in grain yield only in the second year after amelioration. Differences in crop development could not be explained by any single soil parameter, suggesting that it was rather a combined effect of loosened subsoil and better supply of subsoil resources that resulted in an increase in subsoil root length density and subsequently led to better crop performance.

Benefits of organic amendments on soil C stock may be offset by increased methane flux in rice paddy field

Periodic application of organic manure (OM) has been suggested to increase soil carbon stock and mitigate global warming. However, in irrigated rice fields, OM amendment greatly increases methane (CH4) emissions, which in turn may offset the effect of increased soil carbon storage on mitigating global warming. Research on the effects of OM application on net global warming potential that integrates greenhouse gas (GHG) fluxes and soil carbon stocks change in rice cultivating systems has been elusive. To determine the impact of organic amendments on global warming in a rice paddy, chemical (NPK) and organic fertilization were installed, and straw removal and recycling plots were added in two fertilization treatments. Annual CH4 and nitrous oxide (N2O) fluxes were evaluated using the static closed chamber method. Soil C stock changes were estimated using the net ecosystem C budget (NECB) which indicates the difference between C input and output. In chemical fertilization, straw removal decreased soil C stock by an average of 751 kg C ha−1 year−1, but straw recycling significantly increased soil C stock by an average of 464 kg C ha−1 year−1. In organic fertilization, soil C stock was strongly affected by cover crop productivity. Under favorable climatic conditions for cover cropping, soil C stocks were greatly increased by green manuring and even more so by straw recycling. However, under an unfavorable climate, soil C stock was not statistically increased, regardless of straw addition. Straw recycling increased annual CH4 flux by approximately 220–310 and 130–190% over straw removal in chemical (7.9 Mg CO2-eq. ha−1 year−1) and organic fertilization (40 Mg CO2-eq. ha−1 year−1), respectively, but negligibly affected N2O flux. Irrespective of fertilization background, net GWP was mainly decided by CH4 flux with 54–98% coverage, and then followed by soil C stock change and N2O flux. As a result, straw addition increased net GWP by around 110–140 and 120–150% over straw removal in chemical and organic fertilization, respectively. Rice yield was stable between years in the chemical fertilization but showed a big difference in organic fertilization, due to the difference in cover crop biomass productivity. However, rice productivity was not significantly affected by straw recycling. Organic amendment and straw applications increased greenhouse gas intensity (GHGI) by an average of 131% and 269% in a rice paddy, respectively, due to a high increase of CH4 flux but a low increase of soil C stock. In conclusion, more effective OM management which can decrease CH4 emissions and increase SOC stock is required in rice paddies.

Determination of Crop Soil Quality for Stevia rebaudiana Bertoni Morita II Using a Fuzzy Logic Model and a Wireless Sensor Network

Stevia rebaudiana Bertoni Morita II, a perennial plant native to Paraguay and Brazil, is also widely cultivated in the state of Colima, Mexico, for its use as a sweetener in food and beverages. The optimization of soil parameters is crucial for maximizing biomass production and stevioside levels in stevia crops. This research presents the development and implementation of a monitoring system to track essential soil parameters, including pH, temperature, humidity, electrical conductivity, nitrogen, phosphorus, and potassium. The system employs a wireless sensor network to collect quasi-real-time data, which are transmitted and stored in a web-based platform. A Mamdani-type fuzzy logic model is utilized to process the collected data and provide farmers an integrated assessment of soil quality. By comparing the quality data output of the fuzzy logic model with a linear regression model, the system demonstrated acceptable performance, with a determination coefficient of 0.532 for random data and 0.906 for gathered measurements. The system enables farmers to gain insights into the soil quality of their stevia crops and empowers them to take preventive and corrective actions to improve the soil quality specifically for stevia crops.

Increasing rye cover crop biomass production after corn residue removal to balance economics and soil health

Low or variable cover crop (CC) biomass production could limit CC benefits. Longer CC growing periods via late termination could increase CC benefits, especially under limited crop residue return. We studied whether early (2–3 wk before planting)- or late (at planting)-terminated winter rye (Secale cereale L.) CC maintains soil properties, crop yields, and farm income under 0%, 25%, 50%, 75%, and 100% corn (Zea mays L.) residue removal in rainfed and irrigated no-till in the U.S. Great Plains after 6 yr. Early-terminated CCs produced < 1 Mg ha-1 of biomass while late-terminated CCs averaged 1.6 Mg ha-1 at the rainfed site and 3.0 Mg ha-1 at the irrigated site. At the rainfed site, CC termination date did not affect soils, but ≥ 75% residue removal reduced soil organic matter (OM) fraction concentrations and 100% reduced mean weight diameter of water-stable aggregates (MWD) in the 0–5 cm depth. At the irrigated site, late-terminated CC increased MWD by 0.22 mm and OM concentration by 5.1 g kg-1 compared with no CC. At the same site, 100% residue removal reduced microbial biomass, while ≥ 50% removal reduced OM concentration by 7.6 g kg-1, available water, and MWD by 0.75 mm relative to no removal. Cover crops only partially offset the adverse effects of residue removal if biomass production was 3 Mg ha-1 yr-1. Corn yield was generally unaffected. High residue removal rates offset CC-induced reduction in net income. Overall, late-terminated CC partially maintains soil health indicators following residue removal and minimally impacts crop yields and economics.

Crop Productivity Boosters: Native Mycorrhizal Fungi from an Old-Growth Grassland Benefits Tomato (Solanum lycopersicum) and Pepper (Capsicum annuum) Varieties in Organically Farmed Soils.

This paper investigates the response of five tomato and five pepper varieties to native arbuscular mycorrhizal (AM) fungal inoculation in an organic farming system. The field experiment was conducted across a growing season at a working organic farm in Lawrence, KS, USA. The researchers hypothesized that native AM fungi inoculation would improve crop biomass production for both crop species, but that the magnitude of response would depend on crop cultivar. The results showed that both crops were significantly positively affected by inoculation. AM fungal inoculation consistently improved total pepper biomass throughout the experiment (range of +2% to +8% depending on the harvest date), with a +3.7% improvement at the final harvest for inoculated plants. An interaction between pepper variety and inoculation treatment was sometimes observed, indicating that some pepper varieties were more responsive to AM fungi than others. Beginning at the first harvest, tomatoes showed a consistent positive response to AM fungal inoculation among varieties. Across the experiment, AM fungi-inoculated tomatoes had +10% greater fruit biomass, which was driven by a +20% increase in fruit number. The study highlights the potential benefits of using native AM fungi as a soil amendment in organic farmed soils to improve pepper and tomato productivity.

Evaluating Critical Nitrogen Dilution Curves for Assessing Maize Nitrogen Status across the US Midwest

Plant N concentration (PNC) has been commonly used to guide farmers in assessing maize (Zea mays L.) N status and making in-season N fertilization decisions. However, PNC varies based on the development stage. Therefore, a relationship between biomass and N concentration is needed (i.e., critical N dilution curve; CNDC) to better understand when plants are N deficient. A few CNDCs have been developed and used for plant N status diagnoses but have not been tested in the US Midwest. The objective of this study was to evaluate under highly diverse soil and weather conditions in the US Midwest the performance of CNDCs developed in France and China for assessing maize N status. Maize N rate response trials were conducted across eight US Midwest states over three years. This analysis utilized plant and soil measurements at V9 and VT development stages and final grain yield. Results showed that the French CNDC (y = 34.0x−0.37, where y is critical PNC, and x is aboveground biomass) was better with a 91% N status classification accuracy compared to only 62% with the Chinese CNDC (y = 36.5x−0.48). The N nutrition index (NNI), which is the quotient of the measured PNC and the calculated critical N concentration (Nc) based on the French CNDC was significantly related to soil nitrate-N content (R2 = 0.38–0.56). Relative grain yield on average reached a plateau at NNI values of 1.36 at V9 and 1.21 at VT but for individual sites ranging from 0.80 to 1.41 at V9 and from 0.62 to 1.75 at VT. The NNI threshold values or ranges optimal for crop biomass production may not be optimal for grain yield production. It is concluded that the CNDC developed in France is suitable as a general diagnostic tool for assessing maize N status in US Midwest. However, the threshold values of NNI for diagnosing maize N status and guiding N applications vary significantly across the region, making it challenging to guide specific on-farm N management. More studies are needed to determine how to effectively use CNDC to make in-season N recommendations in the US Midwest.

Validation of a metabolite-GWAS network for Populus trichocarpa family 1 UDP-glycosyltransferases.

Metabolite genome-wide association studies (mGWASs) are increasingly used to discover the genetic basis of target phenotypes in plants such as Populus trichocarpa, a biofuel feedstock and model woody plant species. Despite their growing importance in plant genetics and metabolomics, few mGWASs are experimentally validated. Here, we present a functional genomics workflow for validating mGWAS-predicted enzyme-substrate relationships. We focus on uridine diphosphate-glycosyltransferases (UGTs), a large family of enzymes that catalyze sugar transfer to a variety of plant secondary metabolites involved in defense, signaling, and lignification. Glycosylation influences physiological roles, localization within cells and tissues, and metabolic fates of these metabolites. UGTs have substantially expanded in P. trichocarpa, presenting a challenge for large-scale characterization. Using a high-throughput assay, we produced substrate acceptance profiles for 40 previously uncharacterized candidate enzymes. Assays confirmed 10 of 13 leaf mGWAS associations, and a focused metabolite screen demonstrated varying levels of substrate specificity among UGTs. A substrate binding model case study of UGT-23 rationalized observed enzyme activities and mGWAS associations, including glycosylation of trichocarpinene to produce trichocarpin, a major higher-order salicylate in P. trichocarpa. We identified UGTs putatively involved in lignan, flavonoid, salicylate, and phytohormone metabolism, with potential implications for cell wall biosynthesis, nitrogen uptake, and biotic and abiotic stress response that determine sustainable biomass crop production. Our results provide new support for in silico analyses and evidence-based guidance for in vivo functional characterization.

Gas Exchanges and Agricultural Performance of Cover Plants in Compacted Soil After Soybean Cultivation

ABSTRACT The present study sought to evaluate gas exchange and biomass production in cover crops grown in soils with different levels of compaction, after soybean cultivation. Experimental design was completely randomized in 4 × 4 factorial scheme, with the factors being composed of four levels of soil density (1.0 ± 0.013; 1.15 ± 0.022; 1.30 ± 0.035 and 1.45 ± 0.040 Mg.m−3) and four cover crops (Avena strigosa Schreb.; Crotalaria juncea L.; Urochloa brizantha cv. Piatã and Crotalaria spectabilis Roth), with three repetitions. Net photosynthesis rate and the transpiration of cover plants were not influenced by soil compaction, unlike the SPAD index of U. brizantha, which improved performance in the photosynthetic process with increasing soil density. All cover plant species show a reduction in shoot dry biomass starting at a density of 1.00 Mg.m−3, as well as the dry biomass and root volume in the compacted layer and below the compacted layer for A. strigosa Schreb and U. brizantha and, with lower root volumes for C. juncea L. and C. spectabilis Roth in the layer below the compacted. U. brizantha showed the best root development in density of 1.45 Mg.m−3, and a greater number of roots per shoot dry biomass, being good alternatives for the preventive management of compaction in compacted soils. Root growth was higher above and below the compacted layer.