Search

Timely and cost-effective crop yield prediction is vital in crop management decision-making. This study evaluates the efficacy of Unmanned Aerial Vehicle (UAV)-based Vegetation Indices (VIs) coupled with Machine Learning (ML) models for corn (Zea mays) yield prediction at vegetative (V6) and reproductive (R5) growth stages using a limited number of training samples at the farm scale. Four agronomic treatments, namely Austrian Winter Peas (AWP) (Pisum sativum L.) cover crop, biochar, gypsum, and fallow with sixteen replications were applied during the non-growing corn season to assess their impact on the following corn yield. Thirty different variables (i.e., four spectral bands: green, red, red edge, and near-infrared and twenty-six VIs) were derived from UAV multispectral data collected at the V6 and R5 stages to assess their utility in yield prediction. Five different ML algorithms including Linear Regression (LR), k-Nearest Neighbor (KNN), Random Forest (RF), Support Vector Regression (SVR), and Deep Neural Network (DNN) were evaluated in yield prediction. One-year experimental results of different treatments indicated a negligible impact on overall corn yield. Red edge, canopy chlorophyll content index, red edge chlorophyll index, chlorophyll absorption ratio index, green normalized difference vegetation index, green spectral band, and chlorophyll vegetation index were among the most suitable variables in predicting corn yield. The SVR predicted yield for the fallow with a Coefficient of Determination (R2) and Root Mean Square Error (RMSE) of 0.84 and 0.69 Mg/ha at V6 and 0.83 and 1.05 Mg/ha at the R5 stage, respectively. The KNN achieved a higher prediction accuracy for AWP (R2 = 0.69 and RMSE = 1.05 Mg/ha at V6 and 0.64 and 1.13 Mg/ha at R5) and gypsum treatment (R2 = 0.61 and RMSE = 1.49 Mg/ha at V6 and 0.80 and 1.35 Mg/ha at R5). The DNN achieved a higher prediction accuracy for biochar treatment (R2 = 0.71 and RMSE = 1.08 Mg/ha at V6 and 0.74 and 1.27 Mg/ha at R5). For the combined (AWP, biochar, gypsum, and fallow) treatment, the SVR produced the most accurate yield prediction with an R2 and RMSE of 0.36 and 1.48 Mg/ha at V6 and 0.41 and 1.43 Mg/ha at the R5. Overall, the treatment-specific yield prediction was more accurate than the combined treatment. Yield was most accurately predicted for fallow than other treatments regardless of the ML model used. SVR and KNN outperformed other ML models in yield prediction. Yields were predicted with similar accuracy at both growth stages. Thus, this study demonstrated that VIs coupled with ML models can be used in multi-stage corn yield prediction at the farm scale, even with a limited number of training data. [ABSTRACT FROM AUTHOR]

Root-lesion nematodes, Pratylenchus spp., are economically important pathogens because of their detrimental and economic impact on a wide range of crops. In August 2018, two samples of both roots and rhizosphere soil were collected from a corn field in Liangyuanqu of Shangqiu city, Henan Province, China. Root-lesion nematodes were recovered from the roots and soil samples using the modified Baermann funnel extraction method. Both the morphological characters and molecular analysis of the internal transcribed spacer (ITS) and D2-D3 expansion region of 28S ribosomal RNA sequences confirmed that the root-lesion nematode population collected from corn in this study was P. neglectus. Phylogenetic analyses showed that this isolate formed a highly supported clade with other P. neglectus isolates. To the best of our knowledge, this is the first report of P. neglectus on corn in Henan Province of China. This study reports the first partial sequences of 28S D2-D3 region of P. neglectus on corn in China. Due to the great harmfulness of root-lesion nematodes to corn, care should be taken to prevent the spread of P. neglectus to other regions in China. At the same time, further study on the biological characteristics of P. neglectus is needed, which will be helpful to develop corresponding management and control strategies.

Timely and cost-effective crop yield prediction is vital in crop management decision-making. This study evaluates the efficacy of Unmanned Aerial Vehicle (UAV)-based Vegetation Indices (VIs) coupled with Machine Learning (ML) models for corn (Zea mays) yield prediction at vegetative (V6) and reproductive (R5) growth stages using a limited number of training samples at the farm scale. Four agronomic treatments, namely Austrian Winter Peas (AWP) (Pisum sativum L.) cover crop, biochar, gypsum, and fallow with sixteen replications were applied during the non-growing corn season to assess their impact on the following corn yield. Thirty different variables (i.e., four spectral bands: green, red, red edge, and near-infrared and twenty-six VIs) were derived from UAV multispectral data collected at the V6 and R5 stages to assess their utility in yield prediction. Five different ML algorithms including Linear Regression (LR), k-Nearest Neighbor (KNN), Random Forest (RF), Support Vector Regression (SVR), and Deep Neural Network (DNN) were evaluated in yield prediction. One-year experimental results of different treatments indicated a negligible impact on overall corn yield. Red edge, canopy chlorophyll content index, red edge chlorophyll index, chlorophyll absorption ratio index, green normalized difference vegetation index, green spectral band, and chlorophyll vegetation index were among the most suitable variables in predicting corn yield. The SVR predicted yield for the fallow with a Coefficient of Determination (R2) and Root Mean Square Error (RMSE) of 0.84 and 0.69 Mg/ha at V6 and 0.83 and 1.05 Mg/ha at the R5 stage, respectively. The KNN achieved a higher prediction accuracy for AWP (R2 = 0.69 and RMSE = 1.05 Mg/ha at V6 and 0.64 and 1.13 Mg/ha at R5) and gypsum treatment (R2 = 0.61 and RMSE = 1.49 Mg/ha at V6 and 0.80 and 1.35 Mg/ha at R5). The DNN achieved a higher prediction accuracy for biochar treatment (R2 = 0.71 and RMSE = 1.08 Mg/ha at V6 and 0.74 and 1.27 Mg/ha at R5). For the combined (AWP, biochar, gypsum, and fallow) treatment, the SVR produced the most accurate yield prediction with an R2 and RMSE of 0.36 and 1.48 Mg/ha at V6 and 0.41 and 1.43 Mg/ha at the R5. Overall, the treatment-specific yield prediction was more accurate than the combined treatment. Yield was most accurately predicted for fallow than other treatments regardless of the ML model used. SVR and KNN outperformed other ML models in yield prediction. Yields were predicted with similar accuracy at both growth stages. Thus, this study demonstrated that VIs coupled with ML models can be used in multi-stage corn yield prediction at the farm scale, even with a limited number of training data.

Heavy metal pollution is a significant environmental problem and has a negative impact on human health and agriculture. Phytoremediation has recently emerged as an efficient heavy metal remediation technology. To examine the phytoremediation potential, an experiment was conducted, where the influence of high and low concentrations of heavy metals, lead, cadmium and zinc (Pb, Cd and Zn) on the phenological characteristics of corn (Zea mays), as well as their accumulation in the underground and aboveground part was monitored. The experiment was carried out in outdoor conditions in pots in which corn was planted and the soil was contaminated with heavy metals in concentrations below and above the maximum allowable concentration prescribed by the Ordinance. The experiment lasted 45 days. By processing the results, statistically significant differences in plant development were determined. The highest concentration of Zn was recorded in the aboveground part of the plant, the stem in the amount of 24.443 mg/kg, and the lowest concentration in the leaf 0.216 mg/kg. The highest concentrations of Cd and Pb were recorded in the root, for lead 26.610 mg/kg and in the stem for cadmium 30.490 mg/kg, which is a statistically significantly higher established value compared to other parts of the plant. [ABSTRACT FROM AUTHOR]

This study was carried out for two years in Göllü village in the Artuklu district of Mardin province in 2015 and 2016 as the second product (June-November period). Commercial hybrid maize variety Dekalp 5401 (Ç1) and Limagrain Helen (Ç2) were used as materials of the field application. The trial was conducted in three iterations according to 'Split Plots in Coincidence Blocks' trial plan. In the study, fertilizer-free control parcel, standard commercial fertilizer (8 kg da-1 P2O5, 20 kg da-1 N), chicken manure (1000 kg da-1), farm manure (1500 kg da-1) and worm manure (1200 kg da- 1) are grouped as G1, G2, G3, G4 and G5 respectively. In this study, besides the grain yield, the content of some macro (K, Na, Mg and Ca) and micro (Fe, Cu, Zn and Mn) elements in the grain were examined. According to the results obtained in the research; while the highest grain yield is obtained in G2 (standard fertilizer) application of Ç1 with 1223 kg da-1, K ratio in G2 and G5 applications of Ç1; Na ratio in G1 and G2 applications in G1 and G2; Mg ratio in G2 applications of both types; and Ca ratio in G2 application of Ç2 are the highest. While iron (Fe) and Zn ratio were obtained in G3 application of Ç1; Cu ratio was obtained in G2 and G4 applications of Ç2; and Mn ratio was obtained in G2 application of Ç1. It has been concluded that G2 application is successful in terms of grain yield and G2 application has an important place in other organic fertilizer sources in terms of macro elements such as N, P, K, Ca and Mg and the content of micro elements such as Fe, Cu, Zn and Mn. [ABSTRACT FROM AUTHOR]

THIS STUDY aimed to investigate the response of maize to supper absorbent polymer (SAP) and exopolysaccharides (EPS) producing bacteria under drought stress conditions at Panjar El -Soukkar region, Alexandria government, Egypt. The functional groups and heavy metal contents of SAP were determined. The swelling capacity of the polymer increased with increasing the hydrolysis time up to 30 min and the de-swelling water ratios of the polymer varied from 0.25 to 8 days. EPS-producing bacteria, Klebsiella oxytoca, Serratia marcescens, and Pseudomonas aeruginosa were selected and classified based on their phenotypic, biochemical, and also their molecular criteria.The EPS production by the selected isolates ranged from 0.85 to 1.24 g/100ml and the total activity of antioxidant of the extracted EPS ranged from 1.464 to 1.827%. The bacterial isolates could tolerate up to -2.24 MPa of water stress and their production of EPS increased with increasing drought stress levels. Different plant growth promoting parameters of selected isolates were evaluated. Two field experiments were conducted during 2018 and 2019 summer growing seasons. The obtained data revealed that drought stress had significant adverse effects on growth and yield parameters of maize plant, NPK uptake by grains, nutrient availability and microbial activities in soil. Seed bacterization of maize with EPS-producing bacterial isolates in combination with SAP improved all measured characters compared to PGPR inocula or SAP used alone. The findings suggested that applying superabsorbent polymer in combination with EPS-producing bacteria could improve tolerance of maize plant toward drought. [ABSTRACT FROM AUTHOR]

The rapid adoption of glyphosate-resistant crops at the end of the 20th century caused a simplification of weed management that relied heavily on glyphosate for weed control. However, the effectiveness of glyphosate has diminished. A greater understanding of trends related to glyphosate use will shed new light on weed adaptation to a product that transformed global agriculture. Objectives were to (1) quantify the change in weed control efficacy from postemergence (POST) glyphosate use on troublesome weeds in corn and soybean and (2) determine the extent to which glyphosate preceded by a preemergence (PRE) improved the efficacy and consistency of weed control compared to glyphosate alone. Herbicide evaluation trials from 24 institutions across the United States of America and Canada from 1996 to 2021 were compiled into a single database. Two subsets were created; one with glyphosate applied POST, and the other with a PRE herbicide followed by glyphosate applied POST. Within each subset, mean and variance of control ratings for seven problem weed species were regressed over time for nine US states and one Canadian province. Mean control with POST glyphosate alone decreased over time while variability in control increased. Glyphosate preceded by a labeled PRE herbicide showed little change in mean control or variability in control over time. These results illustrate the rapid adaptation of agronomically important weed species to the paradigm-shifting product glyphosate. Including more diversity in weed management systems is essential to slowing weed adaptation and prolonging the usefulness of existing and future technologies., (Published by Oxford University Press on behalf of National Academy of Sciences 2023.)

Nitrous oxide (N2O) is a major greenhouse gas and cultivated soils are the most important anthropogenic source. N2O production and consumption are known to occur at depths below the A or Ap horizon, but their magnitude in situ is largely unknown. At a site in SW Michigan, USA, we measured N2O concentrations at different soil depths and used diffusivity models to examine the importance of depth-specific production and consumption. We also tested the influence of crop and management practices on subsurface N2O production in (1) till versus no-till, (2) a nitrogen fertilizer gradient, and (3) perennial crops including successional vegetation. N2O concentrations below 20 cm exceeded atmospheric concentrations by up to 900 times, and profile concentrations increased markedly with depth except immediately after fertilization when production was intense in the surface horizon, and in winter, when surface emissions were blocked by ice. Diffusivity analysis showed that N2O production at depth was especially important in annual crops, accounting for over 50% of total N2O production when crops were fertilized at recommended rates. At nitrogen fertilizer rates exceeding crop need, subsurface N2O production contributed 25–35% of total surface emissions. Dry conditions deepened the maximum depth of N2O production. Tillage did not. In systems with perennial vegetation, subsurface N2O production contributed less than 20% to total surface emissions. Results suggest that the fraction of total N2O produced in subsurface horizons can be substantial in annual crops, is low under perennial vegetation, appears to be largely controlled by subsurface nitrogen and moisture, and is insensitive to tillage. [ABSTRACT FROM AUTHOR]

Corn production in less planr sensity has been struggled over the last decades with differnt degrees of accomplishment. This research was conducted on the second crop growing season in 2016 at the Mustafa Kemal Univertiy, Turkey to determine the optimum plant density (8, 9, 10, and 11 plant/m2) for two different maturitiy groups hybrid corn varieties of P31 P 41 (FAO 650) and DKC 5741 (FAO 500). Tasseling time, plant height, stem diameter, stalk length, cob thickness, wedge weight, SPAD, leaf area index, harvest index and grain yield were measured. The results indicated that there were sinificant differences among the plant densities, and between the varieties, and their intercations for almost all the growth and yield trains of hybrid corn varieties. For the plant density, wider spaced plants (8 plants/m2) produced the highest values of stem diameter (SD), SPAD reading, ear diameter (ED), grain weight (GW), and grain yield (GY) followed by nearest spaced plants (9 plants/m²) as compared to closed spaced plants (10 and 11 plants/m²). Significant varietal differences were recorded in all studied traits except SPAD falue and ED. However, the variety DKC 5741 produced shorter plant, lesser LAI and tasseled earlier but generated higher SD, EL (ear length), GW, and GY than the variety P31 P 41. Therefore, the early maturing maize variety DKC 6547 can be grown with maintaining 8-9 plants/m2 for obtaining maximum grain yield corn. [ABSTRACT FROM AUTHOR]

A direct, controlled comparison of the photodegradation of imazethapyr has been made between imazethapyr in aqueous solutions, imazethapyr on the surface of epicuticular waxes of corn and soybean plants, and imazethapyr on the surface of intact corn and soybean plant leaves. In some experiments, the imazethapyr solutions were allowed to evaporate partially or fully after application to better model environmental conditions. The photodegradation of imazethapyr was fastest in aqueous solutions (k = 0.16 ± 0.02 h−1) and slowest on the surface of corn and soybean plants (kcorn = 0.00048 ± 0.001 h−1 and ksoy = 0.00054 ± 0.003 h−1). Experiments allowing evaporation during irradiation have intermediate rate constants (e.g., kcorn = 0.082 ± 0.005 h−1). Finally, identification of photoproducts was also examined on epicuticular waxes of corn and soybean plants for the first time. [ABSTRACT FROM AUTHOR]

Aspergillus flavus colonization in developing kernels of maize single-cross hybrids resistant (Mp313E × Mp717) and susceptible (GA209 × T173) to aflatoxin accumulation was determined in the field over three growing seasons (2012–2014). Plants were hand pollinated, and individual kernels were inoculated with a needle dipped in a suspension of A. flavus conidia 21 days after pollination. Kernels were harvested at 1- to 2-day intervals from 1 to 21 days after inoculation (DAI). Kernels were placed in FAA fixative, dehydrated, embedded in paraffin, sectioned, and stained with toluidine blue. Kernels were also collected additional kernels for aflatoxin analyses in 2013 and 2014. At 2 DAI, A. flavus hyphae were observed among endosperm cells in the susceptible hybrid, but colonization of the endosperm in the resistant hybrid was limited to the wound site of the resistant hybrid. Sections of the scutellum of the susceptible hybrid were colonized by A. flavus by 5 DAI. Fungal growth was slower in the resistant hybrid compared to the susceptible hybrid. By 10 DAI, A. flavus had colonized a large section of the embryo in the susceptible hybrid; whereas in the resistant hybrid, approximately half of the endosperm had been colonized and very few cells in the embryo were colonized. Fungal colonization in some of the kernels of the resistant hybrid was slowed in the aleurone layer or at the endosperm-scutellum interface. In wounded kernels with intact aleurone layers, the fungus spread around the kernel between the pericarp and aleurone layer with minimal colonization of the endosperm. Aflatoxin B1 was first detected in susceptible kernel tissues 8 DAI in 2013 (14 μg/kg) and 2014 (18 μg/kg). The resistant hybrid had significantly lower levels of aflatoxin accumulation compared to the susceptible hybrid at harvests 10, 21, and 28 DAI in 2013, and 20 and 24 DAI in 2014. Our study found differential A. flavus colonization of susceptible and resistant kernel tissues, and that the aleurone and the outer layer of the scutellum slowed the rate of colonization by A. flavus.

Aspergillus flavus colonization in developing kernels of maize single-cross hybrids resistant (Mp313E × Mp717) and susceptible (GA209 × T173) to aflatoxin accumulation was determined in the field over three growing seasons (2012-2014). Plants were hand pollinated, and individual kernels were inoculated with a needle dipped in a suspension of A. flavus conidia 21 days after pollination. Kernels were harvested at 1- to 2-day intervals from 1 to 21 days after inoculation (DAI). Kernels were placed in FAA fixative, dehydrated, embedded in paraffin, sectioned, and stained with toluidine blue. Kernels were also collected additional kernels for aflatoxin analyses in 2013 and 2014. At 2 DAI, A. flavus hyphae were observed among endosperm cells in the susceptible hybrid, but colonization of the endosperm in the resistant hybrid was limited to the wound site of the resistant hybrid. Sections of the scutellum of the susceptible hybrid were colonized by A. flavus by 5 DAI. Fungal growth was slower in the resistant hybrid compared to the susceptible hybrid. By 10 DAI, A. flavus had colonized a large section of the embryo in the susceptible hybrid; whereas in the resistant hybrid, approximately half of the endosperm had been colonized and very few cells in the embryo were colonized. Fungal colonization in some of the kernels of the resistant hybrid was slowed in the aleurone layer or at the endosperm-scutellum interface. In wounded kernels with intact aleurone layers, the fungus spread around the kernel between the pericarp and aleurone layer with minimal colonization of the endosperm. Aflatoxin B1 was first detected in susceptible kernel tissues 8 DAI in 2013 (14 mg/kg) and 2014 (18 mg/kg). The resistant hybrid had significantly lower levels of aflatoxin accumulation compared to the susceptible hybrid at harvests 10, 21, and 28 DAI in 2013, and 20 and 24 DAI in 2014. Our study found differential A. flavus colonization of susceptible and resistant kernel tissues, and that the aleurone and the outer layer of the scutellum slowed the rate of colonization by A. flavus. [ABSTRACT FROM AUTHOR]

Agronomic characteristics of genetically modified (GM) MON 89034 × TC1507 × NK603 × DAS-40278–9 (PowerCore™ Enlist™), MON 89034 × TC1507 × NK603 (PowerCore™), and DAS-40278–9 (Enlist™) corn, a non-GM near-isogenic hybrid, and 2 commercial non-GM hybrids were assessed in a field study to determine if the agronomic performance of the GM corn hybrids is equivalent to that of non-transgenic hybrid corn. The MON 89034 × TC1507 × NK603 × DAS-40278–9 hybrid corn was developed through stacking of 4 individual transgenic events, MON 89034, TC1507, NK603, and DAS-40278–9 by traditional breeding and contains thecry1A.105andcry2Ab2(MON 89034),cry1Fandpat(TC1507),cp4 epsps(NK603) andaad-1(DAS-40278–9) transgenes. These transgenes encode the proteins Cry1A.105, Cry2Ab2, and Cry1F, which confer insect resistance, PAT, CP4 EPSPS, and AAD-1, which confer herbicide tolerance. The following agronomic characteristics were assessed in the study: initial and final stand count, seedling vigor, time to silk, time to pollen shed, pollen viability, plant height, ear height, stalk lodging, root lodging, days to maturity, stay green, disease incidence, insect damage, herbicide injury, and yield. The agronomic assessment was conducted in 2 regions of Brazil (Indianopolis-MG; Cravinhos-SP). The agronomic attributes for all GM entries were statistically indistinguishable from the non-GM near-isogenic hybrid. In addition, most of the agronomic assessments fell within the range of the commercial varieties included in the study. Taken together, MON 89034 × TC1507 × NK603 × DAS-40278, MON 89034 × TC1507 × NK603, and DAS-40278–9 were found to be agronomically equivalent to non-GM corn. [ABSTRACT FROM PUBLISHER]

The large-scale cultivation of crops may lead to biodiversity decreases as a result of habitat loss and degradation of natural habitats. A popular strategy for enhancing insect diversity in intensively cultivated habitats involves maintaining plant diversity in field margins by means of sown grass and wildflower strips., Despite extensive cultivation of maize/corn (approximately 3.1 million ha) in the grassy biomes of South Africa, little effort has been made to understand whether plant groups maintain insect biodiversity within these agro-ecosystems., The diversity relationships between three prominent guilds of arthropods (herbivores, parasitoids and predators) and three large plant families ( Asteraceae, Fabaceae and Poaceae) are described at regional scale across the Grassland and Savanna Biomes of South Africa., The results obtained indicate general positive relationships between plant and arthropod diversity of the lower vegetation layers (≤2 m)., An increased abundance of members of the grass family ( Poaceae) led to significantly higher invertebrate numbers in maize fields and adjacent vegetation. This suggests that grasses play a significant role in supporting arthropod diversity within these agro-ecosystems., When considering farm design in maize-agro-ecosystems, our results indicate that maintaining grassy natural vegetation patches adjacent to actively cultivated maize fields may be sufficient to maintain and conserve arthropod diversity within agricultural landscapes. [ABSTRACT FROM AUTHOR]

Currently, water scarcity is serious and the irrigation scheduling with efficient water use becomes important in China. In this study, irrigation systems were scheduled in the saline area along Laizhou Bay. Field study was conducted to determine the relation of irrigation regime and crop yield from 2010 to 2012, and the representative rainfall years (high-flow year, normal-flow year and low-flow year) were calculated by analyzing rainfall frequency over 30 years. Six irrigation regimes were set according to local farmers' practices. Irrigation amounts of T1, T2, T3, T4, T5 and T6 were 225.0 mm, 270.0 mm, 337.5 mm, 300.0 mm, 360.0 mm and 450.0 mm, respectively, with the same frequency of four times. The results showed that soil salt content decreased with the increase of irrigation water amounts. The corn yield varied from 6560 kg/hm2 to 8060 kg/hm2. The highest yield was obtained from T5. Production functions related to irrigated water (I, mm) for corn yield (Y, kg/hm2) was Y = -0.0397I2 + 1059.6 (R2 = 0.8892). Aiming at high corn yield, total water supply (irrigation and rainfall) to corn crops was 859 mm. Precipitation amounts at low-flow year (p=80%), normal-flow year (p=50%) and high-flow year (p=20%) were obtained by the simulation of rainfall frequency curve, which were 348 mm, 457 mm and 604 mm respectively in the whole growth period (from late June to mid-October). In order to obtain the highest theoretical corn yield, according to field results and rainfall, the optimum irrigation frequency at low-flow year, normal-flow year or high-flow year was four times for corn in the saline area along Laizhou Bay. [ABSTRACT FROM AUTHOR]

This study investigated the water balance, crop yield, and water use efficiency (WUE) of a water table management system compared to a conventional drainage system at three nitrogen levels. A two-year field study was conducted using three blocks; each block was composed of two water management treatments: controlled drainage with subirrigation (CD-SI) and conventional or free drainage (FD). The water table depth was maintained at 60 cm below the soil surface in the CD-SI plots. Three nitrogen treatments (low, medium, and high) were applied in strips across all blocks. The seasonal water balance indicated surplus water conditions in the CD-SI plots, while the FD plots had deficit conditions. In 2008 and 2009, the corn grain WUE for the FD plots was 2.49 and 2.46 kg m-3 respectively. The corn grain WUE for the CD-SI plots was 2.43 and 2.26 kg m-3 in 2008 and 2009, respectively. The WUE of corn grain responded to the water treatments (p < 0.05) in 2009 but not in 2008. In 2009, at low and high nitrogen levels, the water management treatments demonstrated significant differences (p < 0.05) in grain yields. However, water management demonstrated no significant effect (p > 0.05) on grain yields at the normal nitrogen level. Furthermore, the two water treatments had no effect on the aboveground dry biomass yields in both years. [ABSTRACT FROM AUTHOR]

Taking normal corn, waxy corn, pop corn, and sweet corn as test materials, this paper studied their seed germination and seedling growth under effects of simulated acid rain (pH 6. 0, 5.0, 4. 0, 3. 0, 2. 0, and 1. 0). Simulated acid rain at pH 2. 0-5. 0 had no significant effects on the seed germination and seedling growth, but at pH 1. 0, the germination rate of normal corn, waxy corn, pop corn, and sweet corn was 91. 3%, 68. 7%, 27. 5%, and 11. 7%, respectively. As compared with those at pH 6. 0 (CK), the germination rate, germination index, vigor index, germination velocity, shoot height, root length, shoot and root dry mass, and the transformation rate of stored substances at pH 1. 0 had significant decrease, and the average germination time extended apparently. At pH 1. 0, the effects of acid rain were greater at seedling growth stage than at germination stage, and greater on underground part than on aboveground part. Due to the differences in gene type, normal corn and waxy corn had the strongest capability against acid rain, followed by pop corn, and sweet corn. It was suggested that corn could be categorized as an acid rain-tolerant crop, the injury threshold value of acid rain was likely between pH 1. 0 and pH 2. 0, and normal corn and waxy corn would be prioritized for planting in acid rain-stricken area. [ABSTRACT FROM AUTHOR]

The article discusses results of a study that examines the ammonium sulfate (AMS) and water hardness effect on glyphosate and glufosinate activity in corn in fields near Harrow and Ridgetown, Ontario. The study showed that water hardness has no effect on control of velvetleaf, common lambsquarters, redroot pigweed and annual grasses green foxtail and barnyardgrass. It concludes that AMS and water hardness have little benefit on glyphosate efficacy in corn.

Fifty-one maize samples, intended for animal feed and human consumption, were collected from the four main maize production provinces in Iran and analyzed by high-performance liquid chromatography (HPLC) for contamination by four naturally occurring aflatoxin analogues (AFB1, AFB2, AFG1, and AFG2). AFB1 was detected in 58.3, and 80% of the maize samples obtained from Kermanshah and Mazandaran provinces, respectively. The maximum AFB1 (276.3 μg/kg) and highest level of total aflatoxins (AFT) (316.9 μg/kg) were detected in a maize sample collected from Kermanshah province. The mean aflatoxin level from contaminated samples (52.60 μg/kg) from Kermanshah was significantly higher ( P < 0.0001) than those in maize from the other three provinces and exceeded all the maximum tolerated levels (MTLs) set for AFT in maize. The level of AFB1 in 15.68% of the total samples was above the MTL (5 μg/kg) for AFB1 in maize in Iran. The mean contamination level of AFT (23.86 μg/kg) in the positive samples was higher than MTL for maize in Iran (20 μg/kg) intended for animal feed. The levels of AFB1, AFB2, AFG1, and AFG2 ranged between not detected (<0.1 μg/kg) and 276.3, 30.4, 9.1, and 1.1 μg/kg in maize grain, respectively. [ABSTRACT FROM AUTHOR]

Abstract: The recent emphasis on corn production to meet the increasing demand for bioethanol has resulted in trepidation regarding the sustainability of the global food supply. To assess the potential of alternative crops as sources of bioethanol production, we grew sweet potato (Ipomoea batatas) and cassava (Manihot esculentum) at locations near Auburn, Alabama and Beltsville, Maryland in order to measure root carbohydrate (starch, sucrose, glucose) and root biomass. Averaged for both locations, sweet potato yielded the highest concentration of root carbohydrate (ca 80%), primarily in the form of starch (ca 50%) and sucrose (ca 30%); whereas cassava had root carbohydrate concentrations of (ca 55%), almost entirely as starch. For sweet potato, overall carbohydrate production was 9.4 and 12.7Mgha−1 for the Alabama and Maryland sites, respectively. For cassava, carbohydrate production in Maryland was poor, yielding only 2.9Mgha−1. However, in Alabama, carbohydrate production from cassava averaged ∼10Mgha−1. Relative to carbohydrate production from corn in each location, sweet potato and cassava yielded approximately 1.5× and 1.6× as much carbohydrate as corn in Alabama; 2.3× and 0.5× for the Maryland site. If economical harvesting and processing techniques could be developed, these data suggest that sweet potato in Maryland, and sweet potato and cassava in Alabama, have greater potential as ethanol sources than existing corn systems, and as such, could be used to replace or offset corn as a source of biofuels. [Copyright &y& Elsevier]

Commercial products containing propagules of arbuscular mycorrhizal fungi (AMF) are widely marketed to improve woody plant performance in the landscape. However, the infectivity of these products has rarely been subjected to independent testing. We evaluated commercial AMF inoculants in a series of greenhouse experiments using corn (Zea mays), sorghum (Sorghum bicolor), trident maple (Acerbuergerianum), and sweetbay magnolia (Magnolia virginiana) as host plants. In corn and sorghum, colonization rarely exceeded 5% when plants were treated with commercial inoculants. In contrast, viable lab-cultured inoculant of similar species composition yielded mean colonization percentages of 38 to 61%. Despite the near absence of colonization, commercial inoculants generally improved shoot growth and increased soil nutrient concentrations in a dose-dependent manner. Commercial inoculants had no effect on mycorrhizal colonization or shoot growth of trident maple or sweetbay magnolia liners. Product-treated magnolias grown from seed also developed little or no mycorrhizal colonization, whereas plants treated with a lab-cultured inoculant were 74% colonized. If commercial AMF inoculants are to receive broad acceptance as landscape soil amendments, manufacturers must demonstrate that their products can promote mycorrhizal colonization under the conditions of their intended distribution and use. [ABSTRACT FROM AUTHOR]

Abstract: The effect of thermal processing via autoclaving on modifications of total phenolics, antioxidant activity and functionality of wheat, buckwheat, corn and oats sprouts and seedlings were investigated. Functionality for type 2 diabetes related α-amylase, α-glucosidase inhibition and levo-dihydroxy phenylalanine (l-DOPA) content, hypertension related angiotensin converting enzyme 1 (ACE) inhibition and ulcer related Helicobacter pylori inhibition were evaluated using in vitro assays. Thermal processing in general resulted in tissue browning leading to higher total phenolic content and free radical scavenging-linked antioxidant activity. It increased α-amylase inhibitory activity in buckwheat and oats but decreased in wheat and corn sprouts and seedlings. It increased α-glucosidase inhibitory activity in wheat, buckwheat and oats but decreased in corn sprouts. It reduced the cognitive function/diabetes related l-DOPA content in all grains sprouts and seedlings tested. It increased ACE inhibitory activity in buckwheat and oats, but decreased in wheat and corn sprouts. It also improved the ulcer related H. pylori inhibitory activity in all grain sprouts and seedlings studied. These changes in functionality are suggested to be due to modifications in the total phenolic content and profile by phenolic oxidation or polymerization caused by thermal processing. Therefore, diet designs for chronic disease management will have to consider thermal processing-linked modification of bioactive ingredient profiles. Industrial relevance: Thermal processing altered the total phenolic content and antioxidant activity in winter wheat, buckwheat, corn and oats sprouts and seedlings. It modified the α-amylase inhibitory activity, α-glucosidase inhibitory activity, l-DOPA content, ACE inhibitory activity and H. pylori inhibitory activity of samples. Therefore, the food processing industry and diet design for chronic disease management will have to consider thermal processing-linked modification of bioactive ingredient profiles for more effective health benefits. [Copyright &y& Elsevier]

Abstract: General circulation models (GCMs), used to predict rainfall at a seasonal lead-time, tend to simulate too many rainfall events of too low intensity relative to individual stations within a GCM grid cell. Even if bias in total rainfall is corrected relative to a target location, this distortion of frequency and intensity is expected to adversely affect simulations of crop growth and yield. We present a procedure that calibrates both the frequency and the intensity distribution of daily GCM rainfall relative to a target station, and demonstrate its application to maize yield simulation at a location in semi-arid Kenya. If GCM rainfall frequency is greater than observed frequency for a given month, averaged across years, GCM rainfall frequency is corrected by discarding rainfall events below a calibrated threshold. To correct the intensity distribution, each GCM rainfall amount above the calibrated threshold is mapped from the GCM intensity distribution onto the observed distribution. We used a gamma distribution for observed rainfall intensity, and considered both gamma and empirical distributions for GCM rainfall intensity. At the study location, the proposed correction procedure corrected both the mean and variance of monthly and seasonal GCM rainfall total, frequency and mean intensity. The empirical (GCM)-gamma (observed) transformation overestimated mean intensity slightly. A simple multiplicative shift did a better job of correcting monthly and seasonal rainfall totals, but left substantial frequency and intensity bias. All of the bias correction procedures improved maize yield simulations, but resulted in substantial negative mean bias. This bias appears to be associated with a tendency for the GCM rainfall to be more strongly autocorrelated than observed rainfall, resulting in unrealistically long dry spells during the growing season. Nonlinearity of crop response to the variability of water availability across GCM realizations may also contribute. Averaging simulated yields each year across multiple GCM realizations improved yield predictions. The proposed correction procedure provides an option for using the daily output of dynamic climate prediction models for impact studies in a manner that preserves any useful predictive information about the timing of rainfall within the season. However, its practical utility for yield forecasting at a long lead-time may be limited by the ability of GCMs to simulate rainfall with a realistic time structure. [Copyright &y& Elsevier]

Abstract: Stochastic weather generators are useful for producing daily sequences that reproduce climatic statistics aggregated to, e.g., a monthly time scale, for use with biological simulation models. This paper describes a stochastic weather generator that disaggregates monthly rainfall by adjusting input parameters or by constraining output to match target rainfall totals, and demonstrates its use with a maize crop simulation model at three locations. Constraining generated monthly rainfall to match observations reproduced the cross-correlation between observed amount, frequency and mean intensity of rainfall more nearly than conditioning weather generator parameters on monthly rainfall. The use of stochastically disaggregated observed monthly rainfall accounted for between 55 and 93% of the variance of yields simulated with observed daily rainfall. Constraining weather generator output required roughly an order of magnitude fewer realizations than conditioning input parameters, to achieve 95 or 99% of the asymptotic maximum correlation with yields simulated with observed rainfall. Negative mean bias of yields simulated with rainfall disaggregated by adjusting weather generator parameters may be due to the variance among stochastic realizations and nonlinearity of yield response to water availability. For maize yields simulated with GCM rainfall predictions at Katumani, conditioning frequency parameters on predicted monthly totals gave the lowest systematic and random error with 1000 realizations. However, constraining generated rainfall to monthly predictions gave better results with few realizations. Although most of the predictability of monthly rainfall was associated with predictability of rainfall frequency, there was little benefit from incorporating predicted frequency into stochastic disaggregation. [Copyright &y& Elsevier]

Abstract: The phenylpropanoid pathway (PPP) was stimulated in dark-germinated corn sprouts and light-germinated seedlings through the pentose phosphate and shikimate pathways during sprouting and subsequent growth phase. Overall trends indicated that natural elicitors such as fish protein hydrolysates (FPH), lactoferrin (LF) and oregano extract (OE) did not stimulate phenolics, antioxidant and seed vigour properties of the corn sprouts and seedlings significantly, but were stimulated in certain stages for specific treatments. The general trend of developmental regulation of total phenolics in corn sprouts was a steady increase with germination. The total phenolic content of control increased almost three-fold from days 1–8 (4mg/g FW) of dark germination. In the case of 5ml/l FPH and 2ml/l OE treatment, the highest phenolic content of 4.5mg/g FW on days 8 and 7 of dark germination was observed. The FPH and OE primed light-germinated seedlings had 29 and 22% higher phenolic levels, respectively, compared to control on day 3, which was associated with a 33 and 22% increase, respectively, in growth on the same day. In general, the antioxidant activity also increased with germination and growth for control and all treatments. The highest antioxidant activity was observed in the case of 2ml/l OE treatment for sprouts on day 8 with 81% 1,1-diphenyl-2-picrylhydrazyl (DPPH) inhibition. This higher activity coincided with higher phenolic content, showing that total soluble phenolics were contributing to high antioxidant activity. In the case of light-germinated corn seedlings, the antioxidant activity was high during early growth, suggesting that activity was linked to free soluble phenolics as GPX activity indicates that phenolics were not being partitioned to polymerization or lignification at this stage. In dark-germinated sprouts, higher glucose-6-phosphate dehydrogenase (G6PDH) activity was observed during early germination possibly due to the carbohydrate mobilization from the cotyledons directed towards the high nutrient requirements of the growing sprout. In light-germinated seedlings, the G6PDH activity only in FPH primed treatment peaked on day 3, and this increased activity was maintained throughout late stages. A positive correlation between G6PDH activity, phenolics and growth was observed for all treatments and control. Both in the case of dark-germinated corn sprouts and light-germinated seedlings, a steady increase in the GPX activity was observed as the germination progressed, reflecting the plants’ need for phenolics for lignification and structural development during growth. This study supports the developmental and partial short-term influence of elicitors on the pentose phosphate pathway (PPP), and its mobilization of enhanced phenolics and antioxidant activity. [Copyright &y& Elsevier]

Aflatoxin contamination in corn caused by Aspergillus flavus Link is a serious constraint on economical corn (Zea mays L.) production in the Mississippi Delta. The ecology of A. flavus was evaluated in a 3-year study assessing the spatial variability of soil populations of A. flavus in a Mississippi Delta field under different crops. A 1.07-ha section of the field was laid out in 126 9.2-m2 plots, and soil was sampled in May 2000, March 2001, and April 2002. Aspergillus flavus populations were determined by plating on selective media, and A. flavus colonization was assessed in corn during 2000. Aspergillus flavus populations in soil were significantly (P < 0.01 level) influenced by previous crop. The highest propagule density (794 cfu·g–1) was found following the corn crop in 2001 versus 251 cfu·g–1 soil in 2000 following cotton and 457 cfu·g–1 following wheat in 2002. Aspergillus flavus populations in 2001 and 2002 exhibited a moderate degree of spatial structure, described by spherical and exponential models, respectively, but populations in 2000 exhibited little spatial structure. Colonization of corn kernels by A. flavus in 2000 ranged from 0% to 100% (mean = 15% colonized kernels), and aflatoxin levels ranged from 0 to 1590 ppb (mean = 57 ppb). Aflatoxin levels were randomly distributed in the field and not correlated with A. flavus colonization. Aflatoxin production was found in 43% to 59% of A. flavus soil isolates with the highest incidence in soil populations following corn in 2001. However, 84% of A. flavus isolated from corn kernels produced aflatoxin. Results indicate that within a single field there was a wide range of A. flavus soil propagule densities varying in potential to produce aflatoxin.Key words:Aspergillus flavus, aflatoxins, soil, corn (Zea mays), cotton, wheat, spatial variability. [ABSTRACT FROM AUTHOR]

In the intensely farmed corn-growing regions of the mid-western USA, surface waters have often been contaminated by herbicides, principally as a result of rainfall runoff occurring shortly after application of these to corn and other crops. In some vulnerable watersheds, water quality criteria for chronic human exposure through drinking water are occasionally exceeded. We selected three settings representative of vulnerable corn-region watersheds, and used the PRZM-EXAMS model with the Index Reservoir scenario to predict corn herbicide concentrations in the reservoirs as a function of herbicide properties and use pattern, site characteristics and weather in the watersheds. We compared herbicide application scenarios, including broadcast surface pre-plant atrazine and alachlor applications with a glyphosate pre-plant application, scenarios in which losses of herbicides were mitigated by incorporation or banding, and scenarios in which only glyphosate or glufosinate post-emergent herbicides were used with corn genetically modified to be resistant to them. In the absence of drift, in almost all years a single runoff event dominates the input into the reservoir. As a result, annual average pesticide concentrations are highly correlated with annual maximum daily values. The modeled concentrations were generally higher than those derived from monitoring data, even for no-drift model scenarios. Because of their lower post-emergent application rates and greater soil sorptivity, glyphosate and glufosinate loads in runoff were generally one-fifth to one-tenth those of atrazine and alachlor. These model results indicate that the replacement of pre-emergent corn herbicides with the post-emergent herbicides allowed by genetic modification of crops would dramatically reduce herbicide concentrations in vulnerable watersheds. Given the significantly lower chronic mammalian toxicity of these compounds, and their vulnerability to breakdown in the drinking water treatment process, risks to human populations through drinking water would also be reduced. [ABSTRACT FROM AUTHOR]

The rate of electron transfer from NADH to ferricyanide associated with corn root plasma membrane vesicles was not significantly affected by the presence of Ca2+, Cd2+, Zn2+, or Co2+. However, unlike Ca2+, other tested divalent cations induced an electron transfer-dependent increase in light scattering by the vesicles. The efficacy in inducing the light scattering increase followed the order of Cd2+>Zn2+>Co2+. The extent of the light scattering change increased as the concentration of added Cd2+ increased. Using phase contrast microscopy, the increase in light scattering was related to an expansion of the vesicles. Accompanying the volume increase, a decrease of Cd2+ concentration in the external space was observed by the use of Arsenazo III, a metallochromophore specific for divalent cations. Under a specified electron transfer condition, a similar percentage of decrease over a wide range of initial Cd2+ concentration was detected. The presence of A23187 decreased the rate and extent of light scattering increase and its associated Cd2+ concentration change. However, A23187 had no effect on scattering changes already established by the electron transfer and Cd2+. These results suggest that the NADH linked electron transfer reaction may induce a Cd2+ uptake by the vesicles of corn root plasma membrane with inside-out orientation. [ABSTRACT FROM AUTHOR]

ABSTRACT Given the increase in crop yields and the expansion of agriculture in low fertility soils, deficiency of micronutrients, such as iron, in plants grown in tropical soils has been observed. The aim of this study was to evaluate Fe availability and Fe uptake by corn (Zea mays L.) plants in 13 different soils, at two depths. Iron was extracted by Mehlich-1, Mehlich-3, and CaCl2 (Fe-CC) and was fractionated in forms related to low (Feo) and high (Fed) crystallinity pedogenic oxyhydroxides, and organic matter (Fep) using ammonium oxalate, dithionite-citrate, and sodium pyrophosphate, respectively. In order to relate Fe availability to soil properties and plant growth, an experiment was carried out in a semi-hydroponic system in which part of the roots developed in a nutrient solution (without Fe) and part in the soil (the only source of Fe). Forty-five days after seeding, we quantified shoot dry matter and leaf Fe concentration and content. Fed levels were high, from 5 to 132 g kg-1, and Feo and Fe-CC levels were low, indicating the predominance of Fe as crystalline oxyhydroxides and a low content of Fe readily available to plants. The extraction solutions showed significant correlations with various soil properties, many common to both, indicating that they act similarly. The correlation between the Mehlich-1 and Mehlich-3 extraction solutions was highly significant. However, these two extraction methods were inefficient in predicting Fe availability to plants. There was a positive correlation between dry matter and Fe levels in plant shoots, even within the ranges considered adequate in the soil and in the plant. Dry matter production and leaf Fe concentration and content were positively correlated with Fep concentration, indicating that the Fe fraction related to soil organic matter most contributes to Fe availability to plants.

A currently utilized pre-harvest biocontrol method involves field inoculations with non-aflatoxigenic Aspergillus flavus strains, a tactic shown to strategically suppress native aflatoxin-producing strains and effectively decrease aflatoxin contamination in corn. The present in situ study focuses on tracking the invasion and colonization of an aflatoxigenic A. flavus strain (AF70), labeled with green fluorescent protein (GFP), in the presence of a non-aflatoxigenic A. flavus biocontrol strain (AF36), to better understand the competitive interaction between these two strains in seed tissue of corn (Zea mays). Corn kernels that had been co-inoculated with GFP-labeled AF70 and wild-type AF36 were cross-sectioned and observed under UV and blue light to determine the outcome of competition between these strains. After imaging, all kernels were analyzed for aflatoxin levels. There appeared to be a population difference between the co-inoculated AF70-GFP+AF36 and the individual AF70-GFP tests, both visually and with pixel count analysis. The GFP allowed us to observe that AF70-GFP inside the kernels was suppressed up to 82% when co-inoculated with AF36 indicating that AF36 inhibited progression of AF70-GFP. This was in agreement with images taken of whole kernels where AF36 exhibited a more robust external growth compared to AF70-GFP. The suppressed growth of AF70-GFP was reflected in a corresponding (upto 73%) suppression in aflatoxin levels. Our results indicate that the decrease in aflatoxin production correlated with population depression of the aflatoxigenic fungus by the biocontrol strain supporting the theory of competitive exclusion through robust propagation and fast colonization by the non-aflatoxigenic fungus.