Corn Yield Loss Research Articles

Weed Biology and Ecology Studies: Diversity, Dominance, Population and Weed Growth and Land Use Efficiency in Intercropping Corn (Zea mays l.) with Leguminous Crops in Dryland

The aim of the research is to examine the effect of intercropping corn with leguminous crops on weeds and land use efficiency. The experimental research method was designed using a randomized complete block design (RCBD) with three blocks. The treatments tested were monocrop planting patterns and intercropping between corn and leguminous crops. The results of the research showed that 16 weed species were found with high species diversity, evenness, dominance, and abundance, so that there were six dominant species that existed during plant growth. Peanuts and cowpeas are suitable for intercropping with corn because they can suppress the population and growth of weeds. Soybeans, green beans, and red beans are not suitable because they are not effective in suppressing the population and growth of weeds and compete with corn, so that corn yield losses due to competition are 38.20%–40.96% and due to weed competition, they reach 62.37%–63.77%. The best ecological and agronomic land use efficiency was obtained by intercropping corn with peanuts and cowpeas, with NKL values based on dry biomass weights of 1.90 and 1.89 (NKL > 1) and dry seed weights of 1.79 and 1.78 (NKL > 1).

Weed Biology and Ecology Studies: Diversity, Dominance and Prediction of Yield Loss of Corn (Zea mays L.) Due to Broadleaf Weeds Competition in Dryland

The aim of the research was to determine the diversity, distribution, dominance, and yield loss of corn due to competition from broadleaf weeds. Descriptive research method with direct survey techniques of research objects. Data were collected using 10 sample plots measuring 1 m2, which were placed using random sampling. Observation parameters include the population and dry biomass weight of weeds and corn. The data was analyzed descriptively and comparatively by calculating density, frequency, and dominance to obtain an important value index and summation diminance ratio (SDR). The results of the research showed that 14 species of broad-leaved weeds were found with high species diversity, distribution, dominance, and abundance indices. The competitiveness and relative weighted dominance of six weed species, namely Amaranthus spinusus, Amaranthus gracilis, Synedrella nodiliflora, Acalypha indica, Ageratum conyzoides, and Alternanthera philoxeroides, are higher than those of other weed species, causing corn yield losses of 5.56%–21.90%. Therefore, these six weed species must be controlled.

Diversified crop rotations mitigate agricultural losses from dry weather.

Abstract As changing climates create drought conditions with increasing frequency and severity, there is an urgent need for farmers to adopt agricultural systems that lower the risk of losses during drought. Diverse crop rotations have long been associated with a wide array of economic and environmental benefits, yet cropping systems in the US Midwest and across the world have been simplifying for over a century. Long-term experiments have shown potential for diverse rotations to avoid yield losses under dry conditions, and could be an impactful target in a region overwhelmingly dominated by corn-soy rotation. Here we use Bayesian modeling to show spatial patterns of yield benefits that result from increasing rotational diversity in a range of weather conditions. Data from over 2.2 million field-years reveal that diverse rotations decrease the risk of corn yield losses in dry years in areas that experience these conditions more frequently, while simultaneously increasing yields under favorable conditions across the region. The potential for yield risk mitigation described in the current analysis underscores the critical need for crop rotation adoption as changing climates threaten yield stability in the US and across the globe. We highlight areas where diverse rotations are most likely to improve yields and mitigate risk, amidst spatial heterogeneity in the magnitude of these benefits.

Prediksi Kehilangan Hasil Jagung (Zea mays L.) Akibat Kompetisi Gulma Poaceae di Lahan Kering

This research aims to determine the Poaceae weed species that have a significant effect on corn yield loss in dry land. The research method was descriptive and data collection using survey techniques in 10 sample plots measuring 1 m2 which were placed using random sampling. Observation parameters include the number of species and populations of weeds, the population of corn plants in plot-1 and the dry biomass weight of weeds and corn in plot-1. Quantitative data analysis by calculating relative density, relative frequency and relative dominance values ​​to calculate the importance value index and Summe Diminance Ratio (SDR). The results showed that the diversity, evenness, dominance and abundance of Poaceae weeds in corn plants in dry land was high. So it was found that seven species of weeds were dominant and continued to exist while the corn was growing, namely Paspalum vasginatum Sw., Leersia hexandra Sw., Digitaria longiflora (Retz.) Koel., Digitaria ciliaris (Retz.) Koel., Cynodon dactylon L., Eleusine indica Gaertn., and Panicum repens L. The competitiveness and ability to reduce corn yields of the weeds Paspalum vasginatum, Leersia hexandra and Digitaria longiflora are higher than other weeds, so that corn yield losses due to competition reach 16.45%, 7.48% and 4.40%. The weeds Brachiaria reptans, Axonopus compressus and Echinochloa colonum do not need to be controlled in corn after the plants are 45 DAT, because their competitiveness and ability to eliminate crop yields is very low.

Investigation of management practices to optimize cereal rye cover crop-based weed mitigation in Canadian sweet corn production

Abstract Fall-sown cereal rye has gained popularity as a cover crop in vegetable production due to its weed-suppressive capabilities. However, previous research has shown that replacing preemergence and/or postemergence herbicide applications with roller-crimped rye has variable success at controlling weeds and maintaining vegetable cash crop yields. The objective of this research was to determine whether roller-crimped rye can provide season-long weed control and maintain sweet corn yield. Two rye cultivars (early vs. standard maturity) were compared at three seeding rates (150, 300, and 600 seeds m−2) for their effect on weed control and sweet corn yield. The trial was conducted at three locations: Harrow, ON, and St. Jean-sur-Richelieu, QC, from 2019 to 2021; and Agassiz, BC, in 2019 and 2021. Results suggest that although the early-maturing cultivar allowed for earlier roller crimping in some locations, it was inferior at weed control and resulted in lower sweet corn yield than local standard cultivars. The average rye biomass was lower than the current literature recommendations, and the resulting level of weed control was not high enough to prevent sweet corn yield loss in cover crop treatments. Weed control provided by roller-crimped rye peaked between crimping and 8 wk after crimping and was highest in the standard cultivars sown at 300 and 600 seeds m−2. Preliminary testing of supplemental postemergence weed control showed evidence for sweet corn yields comparable to the weed-free no-cover crop check. However, more research is needed. Overall, with the cultivars and seeding rates tested, roller-crimped rye is not a suitable stand-alone weed control option in sweet corn production. Given the benefits of cover crops, further research should evaluate its potential as a component of an integrated weed management program.

Split fertilizer nitrogen application with a cereal rye cover crop reduces tile nitrate loads in a corn-soybean rotation.

Splitting fertilizer nitrogen (N) applications and using cover crops are management strategies to reduce nitrate in tile drainage water. We investigated split fertilizer N applications to corn (Zea mays L.) on crop yields and tile nitrate loss in both corn and soybean (Glycine max L.) in rotation from 2016 through 2019. We evaluated the inclusion of cover crops in a split-N treatment. Fertilizer N treatments included 100% in the fall; 50% in the fall + 25% at planting + 25% at side-dress; 100% as spring preplant; 75% as spring preplant (reduced N rate); 50% as spring preplant + 50% at side-dress; and 50% as spring preplant + 50% at side-dress with a cover crop. We did not find significant differences between split and single full rate N application treatments for corn yields or tile nitrate loss; however, the reduced N rate treatment significantly decreased corn yield by 10%. Cumulative tile nitrate losses (over four seasons) ranged from 115kg ha-1 for all of the N in the fall to 65kg ha-1 for 50% as spring preplant + 50% at side-dress with a cover crop, a decrease of 43%. Tile nitrate loss responded similarly to (corn) N treatments under both corn and soybean, with 64% of the loss under corn and 36% under soybean. Our results suggest that decreasing the fertilizer N rate may impact corn yield more than nitrate loss, while split fertilizer N application with a cover crop has potential to reduce tile nitrate loss without decreasing crop yield.

Interseeded cover crops did not cause corn yield loss in eastern North Dakota

AbstractNorth Dakota is a transitional semiarid region with annual precipitation in the eastern part of the state of about 50–55 cm, mostly from rainfall. The moisture demand from interseeding cover crops into standing corn (Zea mays) early in the season has been a concern and is likely why most corn growers do not interseed cover crops. Corn grain yield was determined in response to interseeding of cereal rye (Secale cereale) or oat (Avena sativa), radish (Raphanus sativus), and camelina (Camelina sativa) and incremental fertilizer nitrogen (N) application rates for five site‐years in the eastern North Dakota. Fifty‐eight days and 35 days of leaf wetness from dew in 2019 and 2020, respectively, were recorded. Cumulative dew accumulation since cover crop emergence was 5.6 mm and 3.5 mm in 2019 and 2020, respectively. Interseeding and its interactions with fertilizer‐N rate did not influence the grain yield. However, cereal rye produced the most biomass of the cover crop species, but the amount varied with site and growing season conditions. Late October, cereal rye biomass produced was 98.8 kg ha−1 in 2018, 352 kg ha−1 in 2019, and 70.3 kg ha−1 in 2020 at the Gardner site. Interseeding did not reduce grain yield loss compared to control. Outcomes will encourage corn growers to adopt cover crops without any changes in their fertilizer N application.

Interaction of quizalofop-p-ethyl with 2,4-D choline and/or glufosinate for control of volunteer corn in corn resistant to aryloxyphenoxypropionates

AbstractCorn that is resistant to aryloxyphenoxypropionate, known commercially as Enlist™ corn, enables the use of quizalofop-p-ethyl (QPE) as a selective postemergence (POST) herbicide for control of glufosinate/glyphosate-resistant corn volunteers. Growers usually mix QPE with 2,4-D choline or glufosinate or both to achieve broad-spectrum weed control in Enlist corn. The objectives of this study were 1) to evaluate the efficacy of QPE applied alone or mixed with 2,4-D choline and/or glufosinate to control glufosinate/glyphosate-resistant corn volunteers in Enlist corn and 2) to determine the effect of application time (V3 or V6 growth stage of volunteer corn) of QPE-based treatments on volunteer corn control and Enlist corn injury and yield. Field experiments were conducted in Clay Center, NE, in 2021 and 2022. Quizalofop-p-ethyl (46 or 93 g ai ha−1) applied at the V3 or V6 growth stage controlled volunteer corn by ≥88% and ≥95% at 14 and 28 d after treatment (DAT), respectively. QPE (46 g ai ha−1) mixed with 2,4-D choline (800 g ae ha−1) produced 33% less than expected control of V3 volunteer corn in 2021, and 8% less than expected control of V6 volunteer corn in 2022 at 14 DAT. Volunteer corn control was improved by 7% to 9% using the higher rate of QPE (93 g ai ha−1) in a mixture with 2,4-D choline (1,060 g ae ha−1). QPE mixed with glufosinate had an additive effect and interactions in any combinations were additive beyond 28 DAT. Mixing 2,4-D choline can reduce QPE efficacy on glufosinate/glyphosate-resistant corn volunteers up to 14 DAT when applied at the V3 or V6 growth stage; however, the antagonistic interaction did not translate into corn yield loss. Increasing the rate of QPE (93 g ai ha−1) while mixing with 2,4-D choline can reduce antagonism.

First Report of Heterodera zeae Koshy, Swarup & Sethi, 1971 (corn cyst Nematode) Infecting Corn (Zea mays) in Spain.

Heterodera zeae Koshy, Swarup & Sethi, 1971 (corn cyst nematode) is an important disease of corn in several areas of the world, including India, Nepal, Pakistan, Egypt, USA, Greece and Portugal (Subbotin et al., 2010). It is a sedentary semi-endoparasite feeding on corn roots and other Poaceae plants and has been associated with significant yield losses in corn (Subbotin et al., 2010). During autumn 2022 a plant-parasitic nematode survey performed in corn at central-western area of Spain (Talavera de la Reina, Toledo), revealed a commercial field with stunted plants. Nematodes were extracted from soil by centrifugal-flotation method (Coolen, 1979). Corn roots inspection detected infections by immature and mature cysts, and soil revealed also mature live cysts and second-stage juveniles (J2s) with a population density of 1010 eggs and J2s/500 cm3 soil (including eggs from cysts). J2s and cysts were processed to pure glycerine using De Grisse's (1969) method. DNA was isolated from single live fresh J2s specimens for amplifying and sequencing of cytochrome c oxidase subunit II (COII) mitochondrial region using the primer pair species-specific H.Gly-COIIF_inFOR/P116F-1R (Riepsamen et al., 2011); D2 and D3 expansion domains of the 28S rRNA were amplified using the D2A/D3B primers (De Ley et al. 1999); internal transcribed spacer (ITS) region using primers TW81/AB28 (Subbotin et al., 2001); and cytochrome c oxidase subunit 1 (COI) gene was amplified using the primers JB3/JB5 (Bowles et al., 1992). Brown cysts were lemon-shaped with a protruding vulval cone with fenestra ambifenestrate, bullae prominent below underbridge and characteristically arranged in finger-like bullae (Fig. 1). J2 with slightly offset lip region (3-5 annuli), stylet strong with rounded stylet knobs, lateral field with four lines, and tail short and tapering conically. Measurements of cysts (n=10) included body length 559 (432-688) µm, body width 450 (340-522) µm, fenestral length 40 (36-43) µm, semifenestral width 19 (17-21) µm, and vulval slit 40 (35-44) µm. J2 measurements (n=10) included body length 477 (420-536) µm, stylet length 21 (20-22) µm, tail length 51 (47-56) µm, and tail hyaline region 23 (20-26) µm. Morphology and morphometrics of cysts and J2, fit with original description and others from several countries (Subbotin et al., 2010). Two J2s individuals were sequenced for COII region (OQ509010-OQ509011) showing 97.1-98.1% similarity with H. zeae from USA (HM462012). Six almost identical 28S rRNA sequences from J2s (OQ449649-OQ449654) were 99.2-99.4% similar to 28S rRNA sequences of H. zeae from Greece, Afghanistan and USA (GU145612, JN583885, DQ328695). Four identical ITS DNA fragments from J2s (OQ449655-OQ449658) were 97.0-97.8% similar to ITS sequences of H. zeae from Greece, and China (GU145616, MW785771, OP692770). Finally, six COI sequences of 400 bp obtained for J2s (OQ449699-OQ449704) were under 87% similarity to several COI sequences of Heterodera spp. in NCBI, being a new molecular barcoding for identifying this species. On the basis of these results, the cyst nematodes isolated from the corn plants from the central-western area of Spain (Talavera de la Reina, Toledo) were confirmed as H. zeae and up to our knowledge it is the first report in Spain. This is a well-known pest of corn, causing important losses in this crop (Subbotin et al., 2010) and it was previously regulated as a quarantine nematode in the Mediterranean region (EPPO).

Assessing wind damage and potential yield loss in mid-season corn using a geospatial approach

Yield loss due to natural disasters, such as storms with high-speed winds and rainfall, can significantly damage standing corn (Zea mays L.) plants and yield. Using a geospatial approach, the study aimed to estimate green snap wind damage to corn and assess potential yield and economic loss in the Mississippi Delta. Midseason corn (V12–V14) snapping occurred on 8 June 2022. We recorded green snap damage in 13 fields [1.0 to 2.0 hectares (ha−1)] with low (224 kg ha−1) and high (336 kg ha−1) N rates and two different row orientations (north–south and east–west) after the damage. The results indicated no nitrogen rates or row orientation effect on green snap damage. The average yield loss could be ~29.25 kg ha−1, with every 1% increase in green snap wind damage causing significant economic loss to producers. Research methods can help scientists to estimate potential green snap yield loss due to severe winds in the larger fields. Research results can also help estimate potential yield and economic loss to assist producers and other stakeholders in decision-making to prepare for changing weather patterns and unprecedented severe windstorms in the future.

An Estimation of Corn yield losses arising from water shortage by measuring thermalized neutrons

An Estimation of Corn yield losses arising from water shortage by measuring thermalized neutrons

Improved weed mapping in corn fields by combining UAV-based spectral, textural, structural, and thermal measurements.

Spatial-explicit weed information is critical for controlling weed infestation and reducing corn yield losses. The development of unmanned aerial vehicle (UAV)-based remote sensing presents an unprecedented opportunity for efficient, timely weed mapping. Spectral, textural, and structural measurements have been used for weed mapping, whereas thermal measurements-for example, canopy temperature (CT)-were seldom considered and used. In this study, we quantified the optimal combination of spectral, textural, structural, and CT measurements based on different machine-learning algorithms for weed mapping. CT improved weed-mapping accuracies as complementary information for spectral, textural, and structural features (up to 5% and 0.051 improvements in overall accuracy [OA] and Marco-F1, respectively). The fusion of textural, structural, and thermal features achieved the best performance in weed mapping (OA=96.4%, Marco-F1=0.964), followed by the fusion of structural and thermal features (OA=93.6%, Marco-F1=0.936). The Support Vector Machine-based model achieved the best performance in weed mapping, with 3.5% and 7.1% improvements in OA and 0.036 and 0.071 in Marco-F1 respectively, compared with the best models of Random Forest and Naïve Bayes Classifier. Thermal measurement can complement other types of remote-sensing measurements and improve the weed-mapping accuracy within the data-fusion framework. Importantly, integrating textural, structural, and thermal features achieved the best performance for weed mapping. Our study provides a novel method for weed mapping using UAV-based multisource remote sensing measurements, which is critical for ensuring crop production in precision agriculture. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

UJI EFEKTIVITAS KONSENTRASI EKSTRAK DAUN CENGKEH (Syzygium aromaticum L.) BERPELARUT ORGANIK TERHADAP MORTALITAS ULAT GRAYAK (Spodoptera litura F.) HAMA TANAMAN JAGUNG

Corn (Zea mays L.) is one of the most important food crop in the world after rice and wheat. Yield loss in corn due to armyworm (Spodoptera litura F.) in Indonesia can reach 80%. Clove leaf (Syzygium aromaticum L.) is one of the plants that have the potential as a vegetable insecticide to control pests. This study aims to obtain the concentration of clove leaf extract (S. aromaticum) with ethanol organic solvents. The research was carried out at the Plant Pest Laboratory, Faculty of Agriculture, Riau University from February to April 2022. The study was conducted experimentally using a completely randomized design (CRD) consisting of six treatments with four replications that obtained 24 experimental units. The treatments given were several concentrations of clove leaf extract with ethanol organic solvents, namely 0.0%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%. The results showed that the application of clove leaf extract with an organic solvent concentration of 0.8% (8 ml.l-1 water) was the best concentration for total mortality of S. litura based on BNJ test results at 5% level and was able to cause total mortality of 77.50% with an initial time of death of 8 hours after application and lethal time 50 at 21 hours after application, but it has not been said to be effective because it has not reached 80%. A concentration of 1% was an effective concentration for controlling S. litura. because it was able to cause total mortality of 82.50% with an initial time of death 5 hours after application and a lethal time of 50 at 17.50 hours application.

Impact of Acetochlor Rate and Application Timing on Multiple-Herbicide-Resistant Waterhemp Control in Corn and Soybean

Documented 6-way (Groups 2, 4, 5, 9, 14, and 27) and 5-way (Groups 2, 5, 9, 14, and 27) multiple-herbicide-resistant (MHR) waterhemp have been confirmed in the US and Canada, respectively causing corn and soybean yield losses > 70%. The objective of this study was to determine the effect of acetochlor application timing and rate on non-emerged MHR waterhemp control in corn and soybean. Acetochlor is not yet registered in Canada, but it could be useful component of an integrated MHR waterhemp control program. Two studies, one in corn and one in soybean, were conducted in southwestern Ontario, Canada from 2020 to 2022. Three rates of acetochlor were applied preplant (PP), preemergence (PRE) and postemergence (POST) to non-emerged waterhemp. In corn, acetochlor [Emulsifiable Concentrate (EC)] applied at 1,225, 2,100 and 2,950 g ai ha-1 controlled MHR waterhemp 81, 85, and 90%, respectively, at 8 weeks after POST application (WAC). Acetochlor EC applied POST or PRE provided better control than when applied PP at 4, 8, and 12 WAC. In soybean, acetochlor [Capsule suspension (CS)] applied at 1,050, 1,375, and 1,700 g ai ha-1 controlled MHR waterhemp 63, 70, and 74%, respectively, at 8 WAC. The timing of acetochlor CS application did not affect MHR waterhemp control. Acetochlor applied at the low, medium, and high rate reduced waterhemp density by 87, 89, and 92% in corn, and by 82, 84, and 87% in soybean, respectively. The high rate of acetochlor provides acceptable control of MHR waterhemp in corn; control in soybean was inadequate.

Regulation Mechanisms of Nitrogen-Doped Carbon Dots in Enhanced Maize Photosynthesis under Drought Stress

Herein, greenhouse experiments were designed to reveal the role of nitrogen-doped carbon dots (N-CDs) in enhancing maize drought tolerance. Two humidity conditions were created: adequate watering (soil moisture, 75%) and drought stress (soil moisture, 35%). Corn seedlings were harvested after spraying the N-CD solution (5 mg·L–1) on maize leaves for 5 days. The results indicated that foliar application of N-CDs increased the net photosynthesis rate (28.6%) of maize, and the fresh and dry weights of roots and shoots increased by 224.5, 360.0, 230.8, and 63.3% under drought stress, respectively. N-CDs showed high reactive oxygen species (ROS)-scavenging activity, resulting in enhanced superoxide dismutase activity (26.7%) and reduced malondialdehyde enzyme activity (18.9%). Besides, N-CDs could be used as light-harvesting materials to improve the light utilization efficiency, upregulate psbA gene expression (81.7-fold), and promote fast synthesis of the D1 protein, which could repair photosystem II under drought stress. Therefore, foliar-sprayed N-CDs could improve photosynthesis through multiple pathways under drought stress: light harvesting, photoprotection, and light repairing. Then, N-CD exposure reduced the corn yield loss under drought by nearly 30% compared with those of the control groups in a full life cycle study. Therefore, this study found for the first time that N-CD-enabled nanoagriculture could ensure crop growth and yield under drought stress, which would be important for global crop cultivation and a promising alternative to deal with the global climate change.

Performance of the domestic Bt corn event expressing pyramided Cry1Ab and Vip3Aa19 against the invasive Spodoptera frugiperda (J. E. Smith) in China.

The invasive fall armyworm, Spodoptera frugiperda (J.E. Smith), has caused serious corn yield losses and increased the frequency of insecticide spraying on corn in Africa and Asia. Drawing lessons from the use of Bt corn to manage fall armyworm in the Americas, China released a certificate for the genetically modified corn event DBN3601T pyramidally expressing Cry1Ab and Vip3Aa19 for industrialization in 2021. Performance of the DBN3601T event against invasive fall armyworm in China was evaluated by plant tissue-based bioassays and field trials during 2019-2021. In the bioassays, tissues and organs of DBN3601T corn differed significantly in lethality to fall armyworm neonates in the order: leaf > husk > tassel and kernel > silk. In field trials, compared with non-Bt corn, DBN3601T corn greatly suppressed fall armyworm populations and damage; larval density, damage incidence, and leaf damage scores for DBN3601T corn were significantly lower than for non-Bt corn at different vegetative stages, and efficacy against larval populations during the 3 years ranged from 95.24% to 98.30%. A laboratory bioassay and 3-year field trials confirmed that DBN3601T corn greatly suppressed fall armyworm populations and has high potential as a control of this invasive pest, making it a key tactic for integrated management of fall armyworm in China. © 2022 Society of Chemical Industry.

Evidence of sweet corn yield losses from rising temperatures

Crop production is sensitive to anomalous weather conditions, but vegetable crops can be highly sensitive to environmental changes. Using sweet corn data collected on 16,040 fields over a 27-year period, we: (a) estimate yield sensitivities to changes in growing season temperature and total precipitation, (b) estimate critical thresholds in non-linear temperature effects on sweet corn yield across diverse environments, and (c) quantify yield losses from surpassing the upper temperature threshold during anthesis in sweet corn. Our results show growing-season temperatures exceeding 30 ^circ{rm C} were detrimental to crop yield. Each additional degree day spent above 30 ^circ{rm C} during anthesis reduced crop yields by 0.5% and 2% in irrigated and rainfed fields, respectively. This study shows evidence for sweet corn yield losses across broad spatial domains in the wake of climate change and underscores the urgency to accelerate crop adaptation strategies to sustain production of this highly popular crop.

Assessing the impacts of pre-growing-season weather conditions on soil nitrogen dynamics and corn productivity in the U.S. Midwest

Improving nitrogen (N) use efficiency is urgently needed to achieve co-sustainability of agricultural productivity and environmental quality. Environmental conditions and farming management practices affect the N cycle in agroecosystems. Particularly, weather conditions during the pre-growing-season (e.g. winter and early spring for the U.S. Corn Belt) can influence the dynamics of soil inorganic N (SIN) content and have implications for the end-of-season crop yield. Here, we used an advanced agroecosystem model, ecosys, to assess the consequences of different pre-growing-season weather scenarios in terms of both SIN dynamics and crop productivity. We first benchmarked ecosys using extensive N trial data collected across the U.S. Midwest, and found that ecosys captured the N fertilizer-yield responses and field-scale N cycle dynamics. We then used ecosys to conduct multiple experiments by changing the pre-growing-season precipitation and temperature, and assessed how these changes affected soil N dynamics and crop yield. We found that: (1) wetter pre-growing-seasons reduced SIN content through increasing leaching, leading to a reduction in corn grain yield of 0.54–0.86 Mg/ha (5–14%) under no fertilizer and of 0.21–0.33 Mg/ha (1–3%) under the normal N fertilizer rate (167 kg N/ha; Illinois average N fertilizer rate in 2018); yield loss induced by higher pre-growing-season precipitation can be eliminated by applying more N fertilizer in spring; and (2) colder pre-growing-seasons can reduce SIN content through decreased N mineralization and enhanced leaching. Both factors further contribute to corn yield loss of 0.10–0.68 Mg/ha (2–8%) under no fertilizer and of 0.12–0.48 Mg/ha (1–4%) under the normal fertilizer rate; however, in this case adding more fertilizer does not necessarily eliminate the yield loss caused by the colder pre-growing-season, because the lower temperature not only causes SIN deficiency but also reduces early-growing-season active root nutrients uptake and crop N demand by cooling soil temperature. These findings expand our understanding of the impact of weather conditions on crop yield and can inform improvements in N fertilizer use efficiency in the U.S. Midwest agroecosystems.

Rye cover crop and in-furrow fertilizer and fungicide impacts on corn optimum seeding rate and grain yield

Higher corn seeding rates and in-furrow fertilizer and fungicide combinations may be effective tools to overcome early-season corn (Zea mays L.) stress, stand reductions, and yield loss following a rye (Secale cereale L.) cover crop (RCC). The objective of this research trial was to evaluate corn growth and yield response and optimum seeding rate requirement following a RCC and different in-furrow starter treatments. Trials were established at three Kentucky, USA locations (2017–20), 7 site-years to evaluate corn response to seeding rate (49,421–108,726 seeds ha-1) following a RCC and no cover crop, and in-furrow fertilizer (10-34-0) + fungicide (pyraclostrobin) and no in-furrow starter. At 2 of 3 locations, a RCC reduced corn V5 chlorophyll content and grain yield by 3.1% and 2.7%, respectively. The inclusion of an in-furrow starter failed to increase corn yield at any location and no interaction with a RCC was observed. Furthermore, an in-furrow starter reduced corn plant stand by 3.2% at 2 of 3 locations. At Lexington, quadratic regression analysis revealed that a higher corn agronomic optimum seeding rate (AOSR) and economic optimum seeding rate (EOSR) was required to maximize corn following a RCC compared to no cover crop. However, no significant stand loss was observed at this location. Overall, these results suggest that in-furrow fertilizer and fungicide do not ameliorate negative effects from a RCC and may cause negative impacts when applied simultaneously in-furrow. In addition, a higher corn AOSR and EOSR may be required following a RCC to maximize corn yield. However, because the effects of a RCC on AOSR were inconsistent among locations, further research may be required.

Impact of delayed postemergence herbicide application on corn yield based on weed height, days after emergence, accumulated crop heat units, and corn growth stage

AbstractNine field experiments were conducted from 2017 to 2019 in Ontario to determine the impact of early weed interference on corn yield based on corn growth stage, days after emergence (DAE), accumulated crop heat units (CHU), and weed size. The predicted weed size at herbicide application that resulted in a 1%, 2.5%, 5%, 10%, 25%, and 50% yield loss in corn was estimated to be 1, 4, 11, 53, non-estimable (N est.*), and N est.* cm under low weed density and 3, 5, 7, 11, 27, and N est.* cm under high weed density, respectively. The predicted DAE at herbicide application time that resulted in a 1%, 2.5%, 5%, 10%, 25%, and 50% yield loss in corn was predicted to be 14, 20, 27, 44, N est.*, and N est.* DAE under low weed density and 5, 7, 11, 17, 25, and 59 DAE under high weed density, respectively. The predicted CHU from planting at herbicide application time that led to a 1%, 2.5%, 5%, 10%, 25%, and 50% yield loss in corn was 468, 636, 821, 1,271, N est.*, and N est.* CHU from planting under low weed density and 207, 283, 385, 551, 972, and 1,748 CHU from planting under high weed density, respectively. The predicted crop stage at herbicide application that led to a 1%, 2.5%, 5%, 10%, 25%, and 50% yield loss in corn was V5, V6, V7, V11, N est.*, and N est.* under low weed density and V1, V2, V3, V4, V8, and V14 under high weed density, respectively. Results indicate that weeds must be controlled before they reach 7 cm in height, prior to 11 d after crop emergence, prior to 385 accumulated CHU from emergence, or prior to the V3 stage under high weed density to avoid greater than 5% yield loss.