Leonardo Deiss

In the US Midwest, liquid manure is most commonly applied on bare soil after fall crop harvest, increasing the risk of nutrient loss during winter and early spring. Applying manure as a side‐dress into standing corn ( Zea mays L.) using tankers or soft drag hose systems can better match seasonal plant N uptake, but producers need evidence that this practice maintains crop yields and reduces excess nitrogen (N) in the soil after harvest. We evaluated paired, on‐farm strip trials across corn fields in Ohio (five counties) during 2022–2023, comparing synthetic fertilizer management with side‐dressed liquid hog (swine) manure. Trials were in a randomized complete block design with three replicates at eight on‐farm sites. Soils (0–20 cm) were sampled pre‐application (Early Season) and post‐harvest (Late Season). Across sites, side‐dressed manure increased corn grain yield by 8.5% on average relative to fertilizer ( p = 0.06) with 12% less first‐year available N that more closely matched seasonal crop N demand and reduced the window for environmental losses relative to fall application. Ear‐leaf nutrients remained unchanged between practices, indicating manure maintained corn nutritional status. Most soil nutrients and soil health indicators were not affected by treatment × sampling time interaction, indicating that side‐dressed manure improved yield without increasing post‐harvest topsoil nutrient surpluses, with exception of side‐dress manure showing higher zinc after corn harvest. Overall, in‐season manure side‐dressing can enhance corn productivity while maintaining post‐harvest topsoil nutrient status under working‐farm conditions.

Managing Kernza [ Thinopyrum intermedium (Host) Barkworth & Dewey] as a dual‐use crop for grain and forage has potential to improve economic viability, particularly in organic systems where premiums and diversified outputs can enhance profitability. We evaluated how the timing and frequency of Kernza forage harvest affected grain and forage yields, forage composition, and weed pressure in organic systems. A 4‐year study (2020–2023) was conducted across five diverse environments in the US Midwest. Four forage harvest strategies coupled with an annual grain harvest were evaluated: (1) a single summer harvest (1x‐Su), (2) spring and summer harvests (2x‐SpSu), (3) fall and summer harvests (2x‐FaSu), and (4) fall, spring, and summer harvests (3x‐FaSpSu). Forage harvest timing and intensity affected forage nutritive value more than grain or total forage yields. Strategies including spring harvests (2x‐SpSu and 3x‐FaSpSu) improved overall nutritive value by increasing total crude protein from 5%–6% to 10% and increasing total relative feed value from 70–80 to 80–92 compared to summer harvest alone (1x‐Su). Grain yields were impacted by stand age, declining substantially over time, ranging from 385–860 kg ha ⁻¹ in Year 1 to 45–224 kg ha ⁻¹ in Year 4 across sites, while forage yields remained relatively stable (2.8–4.8 Mg ha ⁻¹ in Year 1 to 2.2–7.5 Mg ha ⁻¹ in Year 4). Weed biomass was similar among treatments but increased in Year 4, which can be a consideration for termination timing of Kernza. Our findings show that well‐timed forage harvests may improve forage quality without sacrificing productivity, offering organic farmers more flexible and profitable management for this perennial grain crop.

The effects of nitrogen (N) on crop growth when water is limited are unclear in the literature. Using maize as a model system, a field study with two levels of water (100% and 70% plant evapotranspiration) and six levels of N availability (50 – 327 kg N ha-1 as the sum of fertilizer N, irrigation water N, and soil residual inorganic N) was conducted in the US Great Plains Region from 2021 – 2023. Maize grain yield and aboveground biomass increased with N availability with full water, but excess N was detrimental when water was limited. Additionally, excess N depressed maize root biomass relative to moderate N availability when water was limited. Maximum grain yield was achieved with an average of 31% less N under limited water relative to full water. Maximum grain yields with limited water were 36%, 59%, and 30% less than full water for the 2021, 2022, and 2023 growing seasons, respectively. The 2023 season had lower fertilizer N inputs due to residual N accumulation from previous years, yet a yield reduction at the higher N availabilities was still observed in the water limited treatment. Maize N uptake increased with N and was greater with full water. High N uptake, however, was not only uncoupled with and, thus, not co-limiting with water, but depressed grain yield and biomass. Adjusting N inputs based on soil N availability and yield potential is necessary to maximize yields and resource use efficiency and will become increasingly important as water limitations become more common.

Measuring soil health indicators at scale remains a major challenge to implementing soil health management, given the high cost and labour intensity of traditional laboratory analysis. Mid‐infrared diffuse reflectance spectroscopy (mid‐DRIFTS) offers a promising alternative to conventional wet chemistry by enabling rapid, high‐throughput prediction of key soil indicators, while capturing mechanistic links between soil biochemical and mineral composition with soil health properties. This study evaluated the predictive and interpretive potential of mid‐DRIFTS for soil health assessment. We compared the predictive performance of three modelling approaches: partial least squares (PLS), support vector machines (SVM) and neural networks (NN) and tested the added benefit of spectral partitioning, a novel approach in soil Fourier transform infrared (FTIR) spectroscopy. Results demonstrated that spectral partitioning consistently improved model performance across indicators, with root mean squared error (RMSE) reduction of up to 37%, and it was especially beneficial for non‐linear machine learning models (SVM and NN). Indicators including soil organic matter (SOM), permanganate oxidizable carbon (POX‐C) and autoclaved citrate‐extractable (ACE) protein were predicted with high accuracy, while indicators such as mineralizable carbon (Cmin), water‐extractable nitrogen (WEN) and extractable nutrients showed moderate to poor predictive performance. These findings suggest that integrating spectral partitioning into modelling routines is a viable approach for accurately predicting biochemical indicators with strong spectral signals. Furthermore, we examined correlations between mineral and organic functional groups estimated as peak areas in mid‐DRIFTS and soil health indicators. POX‐C and ACE protein were positively associated with aliphatic C–H groups and negatively related to aromatic and clay‐derived mineral functional groups, highlighting the role of biochemical composition and mineral–organic interactions in regulating dynamic soil health properties. Overall, mid‐DRIFTS approaches enable estimation of key soil health indicators while revealing mechanistic links between soil composition and soil health.

The objective of this work was to evaluate the performance and ingestive behavior of singleton and twin lambs after weaning under different feeding systems on tropical pasture. Studies were carried out over three years with castrated and weaned males of Texel x Corriedale lambs. In the first year, the treatments were: grass; grass and supplementation with concentrate (1.5% or 2.5% of live weight); grass and controlled legume grazing. In the second and third years, the treatments were: either grass or legume; mixed, this is, contiguous area of both grass and legume. On tropical pasture system, twin lambs fed with high levels of concentrate can gain more live weight than singletons, showing a compensatory growth and reaching the singletons live weight. Sheep litter size does not affect weaned lambs’ grazing behaviour under different feeding systems on tropical grassland. The use of concentrate supplementation changes lambs’ ingestive behavior by reducing grazing time and increasing idling time. Pigeon pea, as a monoculture or associated with grass, can be an important source of nutrients for lambs; however, it is not sufficient to ensure the same performance of twin and singleton lambs.

Integrated crop-livestock systems (ICLS) foster synergistic relationships to increase nitrogen (N) cycling and soil organic carbon (SOC) accrual in agricultural setups. This study evaluated how the grazing intensity and N fertilization (rates and timing) affect both SOC and N fractions, and soil organic matter chemical composition in an ICLS managed under no-tillage in an Oxisol, six years after initiation. The ICLS was compared to a nearby pasture (PA) and a native forest (NF). The treatments consisted of two grazing intensities: Low Sward Height (LH) and High Sward Height (HH) were maintained with high and low stocking rates, respectively. The HH varied between 0.20 and 0.60 m, and LH between 0.10 and 0.30 m according to the plant forage species throughout the experiment. Fertilization using 200 kg ha ^-1 N-urea, not splitting up, was conducted at two timings, either at the winter pasture establishment (autumn), about 35 days after sowing or during the summer cash crop cycle (spring). Total N amount per year, including both phases, pasture and cash crop was the same for all treatments. The SOC and N contents were assessed in soil and particulate organic matter (POM), while carbon (C) and N stocks were specifically determined in the soil. Soil organic matter composition was characterized by FTIR. The combination of HH and N fertilization during the pasture phase increased the content of C from 36.1 to 39.9 ± 0.7 g C kg ^-1 and of N from 2.7 to 3.2 ± 0.1 g N kg ^-1 . The SOC stocks varied from 37.3 to 41.1 ± 0.7 Mg C ha ^-1 , and the N stocks from 2.1 to 3.3 ± 0.1 Mg N ha ^-1 at 0.0-0.10 m soil layer. The SOC content of the POM and the soil organic matter chemical composition determined by FTIR were mainly affected by the grazing intensity. The HH led to an increased in C content within the POM fraction, reaching values of 51.6 ± 1 and 49.2 g C kg ^-1 , respectively to N crop fertilization and N pasture fertilization. Land-use changed how organic functional groups were stored in soil organic matter fractions. The NF had a greater abundance of aliphatic and phenol in the MAOM, while pasture and ICLS systems had greater aliphatic in the POM fraction. In ICLS, SOC accrual was positively associated with more recalcitrant organic functional groups of phenol, aromatic, and carbonyl C-O. The HH increases SOC accrual, while N-fertilization on pasture ensures adequate nutrition of plants and animals during the winter ICLS phase, at the same time as providing greater residual N for subsequent cash crops through enhanced catalyzed by ruminants. Therefore, grazing and fertilization management strategies should be considered to promote sustainable agriculture intensification with ICLS.

Soil test phosphorus (P) and potassium (K) and the associated soil test critical values (CSTVs) are widely used as the primary diagnostic tool to determine if a crop needs P and K fertilizer. However, identifying robust and predictive CSTVs requires a large number of field trials in representative soils and environments to assess crop fertilizer responses. From 1976 to 2021, a total of 457 P trials and 458 K trials were conducted in corn ( Zea mays ), soybean ( Glycine max ), and wheat ( Triticum aestivum ) across 40 counties in Ohio. The trials consisted of both multi‐rate, multi‐year trials and single‐year, single‐rate and large strip trials. Across all crops, grain yield responded to P and K fertilizer in 23.4% and 25.3% of trials, with average yield increases of 8.8% and 11.0%, respectively. Corn yield was more responsive to P and K fertilizer (∼30% of P and K trials) than soybean yield (14% of P trials, 20% of K trials). Several models were run to identify CSTVs, but models imparted systematic bias in CSTVs, and a superior model was not identified due to poor model fit and indiscernible criteria to guide model selection. Instead of a single CSTV, data were classified into five discrete categories based on relative yields and Mehlich‐3 soil test values. These classifications provided a useful and consistent framework for assessing the probability of crop response to P and K fertilizer. Ohio soils with Mehlich‐3 values greater than 20 mg P kg ⁻¹ and 130 mg K kg ⁻¹ have a low probability of responding to P or K fertilizer application.