Virginia Corn Research Articles

In-season decision support tools for estimating sidedress nitrogen rates for corn in the Mid-Atlantic Coastal Plain

ABSTRACTIn corn (Zea mays L.) production, determining appropriate nitrogen (N) rates is a critical part of achieving profitable yields, while minimizing negative environmental effects. Many tools to assist in the determination of optimum corn sidedress N rates exist, however, those that are low cost, that can be used in real time and that do not require extensive scouting or sampling may be preferred. This study compared the rates prescribed by four in-season N rate recommendation approaches: (1) the Virginia Corn Algorithm (VCA); (2) the Maize-N simulation model; (3) the Nutrient Expert for Maize (NE-Maize) model; and (4) the standard yield goal-based approach used in Virginia for N rate prescription, nitrogen use efficiency (NUE), and corn performance. The VCA uses canopy reflectance from pre-existing high and low N areas to determine potential response to additional N fertilizer. Maize-N generates recommendations based on crop and soil-specific input parameters as well as long-term and current season weather data. The NE-Maize model requires input of site and crop specific data, as well as the history of inputs and crop rotation and generates recommendations based on previous result from studies conducted in similar environments. The purpose of this study was to compare N rate recommendations from these various systems for performance and utility in the mid-Atlantic region. A total of seven field trials were conducted from 2012 to 2014 in Virginia each with four replications in a randomized complete block design. Treatments evaluated included a complete factorial of four different pre-plant rates (0, 45, 90, and 134 kg ha−1) with the three different simulation model-prescribed rates and the yield-goal approach applied at sidedress. There were no differences in corn grain yield between the different systems or pre-plant N rate application at any location. Corn grain and stover N uptake were infrequently affected by treatment, but generally increased with increasing N rate applied, when a difference existed. Partial factor productivity (PFP) of N generally declined with increasing pre-plant N rate for all in-season N recommendation systems. The PFP for the in-season N rate recommendations generated from the VCA approach was greatest in four of seven instances with a mean of 68 kg grain kg N−1. Additionally, based on our results the Maize-N model, 56 kg grain kg N−1, also shows promise in this environment. While additional research is needed to validate these findings, producers should consider the use of sidedress N rate decision support tools to increase efficiency of N fertilizer.

Evaluation of Insecticides for the Control of Lepidopteran Larvae in Sweet Corn in Virginia, 2014: Table 1

Evaluation of Insecticides for the Control of Lepidopteran Larvae in Sweet Corn in Virginia, 2014: Table 1

Illinois Soil Nitrogen Test for Prediction of Fertilizer Nitrogen Needs of Corn in Virginia

Current N needs for corn (Zea mays L.) in Virginia are estimated based on expected yield and are adjusted to account for the estimated amounts of N mineralized from organic sources such as manures, biosolids, and legumes. The dynamic nature of soil N creates significant uncertainty in estimates of N availability from these sources. Accurate quantification of organic N mineralization during the corn growing season should improve the precision of fertilizer N recommendations. The Illinois soil N test (ISNT) has shown promise as a tool for estimating mineralizable soil N and predicting corn fertilizer N needs. Other research has found the ISNT to be poorly related to labile soil N and unrelated to corn response to fertilizer N. The objective of this study was to determine if the ISNT predicts the fertilizer N response of corn grown in a diverse set of Virginia agroecosystems. We conducted 29 on‐farm fertilizer N response trials in major corn‐producing regions of Virginia. The ISNT was significantly related to estimated yield without fertilizer N (R2 = 0.57, P < 0.0001) and relative yield (R2 = 0.64, P < 0.0001). We also found that the ISNT extracted a consistent percentage of total soil N (16.3 ± 0.7%), suggesting that it is a poor indicator of labile N. In fact, total soil N did as well as the ISNT at predicting yield without fertilizer N (R2 = 0.53, P = 0.0002) and relative yield (R2 = 0.64, P < 0.0001). The ISNT offered no more information about corn yield response to fertilizer N than did total soil N content.

Efficacy and economics of fresh-market Bt transgenic sweet corn in Virginia

The effectiveness and cost of managing the suite of insect pests that attack sweet corn in Virginia were evaluated using multiple foliar applications of pyrethroid insecticides and Bt transgenic sweet corn in 2000 and 2002. Several Bt cultivars and their non-transgenic isolines were tested in different locations in Virginia to examine efficacy over a range of growing conditions and pest pressure. Overall, insect damage was far less in the Bt cultivars than in the non-Bt isolines that were not sprayed or sprayed with lambda-cyhalothrin up to six times. When insect pressure was low to moderate, Bt sweet corn did not require supplementary insecticide applications for a high percentage (⩾88%) of ears to be considered fresh-market quality. In contrast, when insect pressure was extremely high, Bt sweet corn required two insecticide applications for a high percentage (⩾88%) of ears to be considered fresh-market quality. Based on an economic comparison between insecticide-treated conventional sweet corn and Bt sweet corn, growers should expect a $547/ha gain by growing Bt sweet corn. If Bt sweet corn was sprayed twice with an insecticide, this gain should be approximately $1777/ha. We conclude that Bt sweet corn is an effective and economically sound pest management strategy for growers in Virginia.

Presidedress soil nitrogen test for corn in Virginia

The presidedress soil nitrate test (PSNT) and the presidedress tissue nitrogen test (PTNT) have been developed to assess residual soil nitrogen (N) sufficiency for corn (Zea mays L.) in the humid eastern U.S. We conducted field studies at 47 sites during 1990 and 1991 to evaluate the use of the PSNT and PTNT for corn in Coastal Plain, Piedmont, and Appalachian Ridge and Valley regions of Virginia. Seven rates of fertilizer N (0, 45, 90, 135, 180, 225, and 270 kg/ha) were applied at corn height of 0.40 to 0.50 m and replicated four times in a randomized complete block design. Whole corn plants and soil to a depth of 0.30 m were sampled when corn height was 0.15 to 0.30 m to estimate available soil N prior to the application of fertilizer N treatments. Corn grain yield response to fertilizer N was used to assess residual soil N availability. Nitrogen concentration of whole corn plants at 0.15 to 0.30 m height was not an accurate indicator of plant‐available soil N. Corn yields were maximized without sidedress N at the 19 sites where soil NO3‐N was at least 18 mg‐kg‐1 and at the 17 sites where soil (NO3+NH4)‐N was at least 22 mg‐kg‐1. The PSNT predicted corn N sufficiency regardless of soil physiographic region or surface texture; however, the critical values for NO3‐N and (NO3+NH4)‐N were 3 to 5 mg‐kg‐1 lower than those established in Pennsylvania and Maryland, where cooler soil temperatures may permit greater residence time of inorganic N.

Risk of Western Corn Rootworm (Coleoptera: Chrysomelidae) Damage to Continuous Corn in Virginia

Information on the risk of western corn rootworm, Diabrotica virgifera virgifera LeConte, damage to continuously-grown corn previously was lacking in Virginia, as well as other mid-Atlantic states. A field study was conducted in 1993 and 1994 comparing root damage, whole-plant yields, and silage quality in insecticide-treated and untreated sections of 32 continuous corn fields in Virginia. Approximately 28% of the fields had serious root damage exceeding a rating of 3.5 (1–6 scale) in sections not treated with a soil insecticide. Also, 19% of the fields had an economic loss in whole-plant yield due to corn rootworm feeding damage. Silage quality, as evidenced by percent crude protein and acid detergent fiber, was not significantly affected by corn rootworm feeding. Because much of the continuous corn acreage in Virginia is treated preventively with soil insecticides for corn rootworms, the results of this study suggest that a large percentage of this insecticide use is unnecessary.

Energy and economic savings from the use of legume cover crops in Virginia corn production

AbstractEnergy analysis provides a measure of the effectiveness of sustainable agricultural systems in reducing inputs purchased from off-farm sources. This study compares the total (direct plus indirect) energy costs of growing corn for silage using manufactured N fertilizer or N-fixing legume cover crops. The cover crop either was killed with herbicide in a no-till system or disked in the spring. Economically competitive alternative crop production practices are identified.In both the no-till and the disked versions, cover-cropped treatments used about half as much energy per hectare as the corresponding winter fallow N-fertilizer treatments. Using vetch to provide N significantly lowered energy use per unit of crop output compared with the N-fertilized treatments. For the treatments that used hairy vetch, either alone or in combination with big/lower vetch, net revenue was statistically equivalent to that of standard-practice treatments in each year of the study.

Incidence of Western Corn Rootworm Beetles (Coleoptera: Chrysomelidae) on Corn in Virginia from 1987 to 1992

The discovery of western corn rootworm beetles, Diabrotica virgifera virgifera LeConte, in a southwest Virginia corn field in 1985 prompted annual surveys of corn fields in an average of 28 counties across the state from 1987 to 1992. All counties included in the annual surveys were representative of the major corn-growing regions of Virginia. Survey results indicated that western corn rootworm beetles spread rapidly throughout most of the western and central continuous corn-growing regions of the state. In the eastern and southeastern corn-growing regions of the state, where crop rotation is widely practiced, detections of western corn rootworm beetles were less common and typically involved only one to two counties per year from 1987 to 1992.

Enhancement of Recruiting Activities to Attract Rural Youth to Careers in Agronomy

Much attention in recent years has been directed toward attracting the nontraditional student to agronomy and other agricultural areas. However, during this time there has been little attention directed toward recruiting efforts targeting rural and farm youth. A proposal to enhance recruiting of such young people to agronomic careers was presented to the Virginia Corn Board, the committee responsible for administering the funds collected from corn grain sold in Virginia. More than 350 letters were sent to members, resulting in 30 student nominees to attend a weekend program at Virginia Polytechnic Institute and State University (VPI & SU) in Blacksburg, Virginia. Of the nominees, 15 were juniors and seniors in high school. These students and their parents were invited to a 2-d program involving faculty and students in the Department of Crop and Soil Environmental Sciences (CSES). Responses were received from 15, and 13 attended. Reactions to the program were positive from both student and faculty perspectives. Of the 13 students who visited, 10 were seniors and three were juniors in high school. All 10 were sufficiently impressed with the college, the department, and programs to seek admission in the fall of 1991. Of the 10, seven were offered admission to VPI & SU, and six accepted, an 86% acceptance rate compared with 63% for the College of Agriculture and Life Sciences as a whole. Two of the three students who were rejected are attending local community colleges with the intention of applying for transfer admission in the fall of 1992. The three junior students all indicated they would seek admission in 1992. The success of this rural and farm student component of an overall recruiting effort has encouraged us to expand the program by submitting similar proposals to other state agricultural commodity groups for additional funding.

Correlation of Zn2+ content with aflatoxin content of corn.

Forty-nine samples from the 1983 Virginia corn harvest were analyzed for aflatoxin, zinc, copper, iron, and manganese content. Values (mean +/- standard deviation) were as follows: aflatoxin, 117 +/- 360 micrograms/kg; zinc, 22.5 +/- 3.4 mg/kg; copper, 2.27 +/- 0.56 mg/kg; iron, 40.8 +/- 18.7 mg/kg; and manganese, 5.1 +/- 1.1 mg/kg. Aflatoxin levels positively correlated with zinc (Spearman correlation coefficient, 0.385; P less than 0.006) and copper levels (Spearman correlation coefficient, 0.573; P less than 0.0001). Based on biochemical data in the literature, we believe that the correlation with zinc is important and that there may be a cause-and-effect relationship between zinc levels in corn and aflatoxin levels which are produced upon infection with Aspergillus flavus or A. parasiticus. Control of aflatoxin contamination in field corn by decreasing the zinc levels may be feasible, but no methods to decrease zinc levels are currently available.

Within-plant and Within-field Distribution of First-generation European Corn Borer (Lepidoptera: Pyralidae) Egg Masses on Field Corn in Virginia

The oviposition site selection by the European corn borer and the within-field pattern of egg mass distribution were studied on field corn in western Virginia. Nearly all egg masses were found on the lowest six leaves of the plant. The within-field distribution of egg masses was found to be a random distribution, as interpreted from the variance/ mean ratio, the method of Taylor and Green's coefficient of dispersion.

Five-Year Study of Mycotoxins in Virginia Wheat and Dent Corn

Every year during the 5-year period 1976-1980, approximately 100 samples each of corn and wheat from trucks delivering the grains at elevators in Virginia were collected by personnel of the Federal Grain Inspection Service and shipped to NRRC. Samples were analyzed as soon as possible for aflatoxin, zearalenone, and ochratoxin A. The 3 mycotoxins were not detected in any wheat sample. Zearalenone and ochratoxin A were not found in any corn sample; however, aflatoxin was detected in at least 25% of the corn samples from every crop year. In 1976-1980, the incidence of aflatoxin at levels of 20 ng/g or more (the Food and Drug Administration guideline) ranged from 18 to 61%; aflatoxin incidence above 100 ng/g was 5-29%. The average aflatoxin levels in corn samples collected in the 5 years varied from 21 to 137 ng/g. Moisture content of the samples was not determined, so aflatoxin levels given may be higher than they were at harvest. However, there are obviously differences from year to year. In freshly harvested corn samples collected by fieldmen of the Statistical Reporting Service in yield surveys in 1978 and 1979, aflatoxin incidence above the FDA guideline was 10 and 13%, and above 100 ng/g was 4 and 7%. The average aflatoxin level in all samples collected in 1978 was 13 ng/g and in 1979, 36 ng/g. Some aflatoxin can be expected yearly in Virginia corn, but the incidence and levels vary from year to year.

Nitrogen for no‐tillage corn in Virginia: Sources and time of application

Abstract No‐tillage corn (Zea mays L.) culture normally entails the placement of N fertilizer on the soil surface without mechanical incorporation. This field investigation was conducted to compare the N fertilizers that are most widely used in Virginia, when applied in this manner, for their effectiveness in producing notillage corn. Comparisons of the time of applying NH4NO3 were also made. Grain and stover yields, in addition to N removed in the crop, were used to draw conclusions. The experiments were conducted on both fertile and infertile soils in 1972 and 1973, both of which were relatively wet years. The fertilizers tested, urea, NH4NO3, and N solutions, were equally effective, per unit of N applied. Split applications of NH4NO3 showed no statistically significant advantage over all applied at planting but slightly trended to do so. N deficiency reduced grain yields relatively more than stover yields.

Comparison of S1 and Testcross Evaluation after Two Cycles of Recurrent Selection in Maize1

Two populations of maize (Zea mays L.), Virginia Corn Belt‐Southern Synthetic (VCBS) which was developed from a broad genetic base, and Virginia Long Ear Synthetic (VLE) which was developed from intercrosses of seven Corn Belt inbred lines, were advanced two cycles of recurrent selection based on S1 and testcross progeny yield. The 10 populations and their diallel crosses were grown at 3 locations with 6 replications at each location. Significant improvement in population yield and combining ability was achieved only with VCBS.S1 selection in VCBS was more effective than testcross selection in increasing both population yield and combining ability. Testcross selection was effective in increasing the frequency of genes that contribute to yield in crosses but not in populations per se whereas S1 selection increased both combining ability and population yield. The yield of the second‐cycle S1 selection population yielded 9.0 q/ha (11%) more than the second‐cycle testcross population and its mean population cross yield was 1.5 q/ha higher. The two populations derived from VCBS by S1 selection produced significantly higher yields when intercrossed or crossed with VCBS than either population derived by testcross selection. S1 selection in VCBS was as effective as testcross selection in increasing the frequencies of genes that contribute to yield, whether in inbred (derived) or hybrid populations.

Yields of S1 Lines from Original and Advanced Synthetic Varieties of Maize1

Four maize (Zea mays L.) synthetic varieties were selfed and approximately 200 S1 lines of each were grown in separate replicated yield trials with the parental populations to compare inbreeding depressions and yield distributions among the S1 lines. The four parental populations were (i) ‘iowa Stiff Stalk Synthetic,’ SSS, (ii) an advanced synthetic derived from SSS by seven cycles of recurrent selection based on half‐sib yield, SSS(HT)C7, (iii) ‘Virginia Corn Belt‐Southern Synthetic,’ CBS, and (iv) an advance synthetic derived from CBS by four cycles of recurrent selection for S1 yield, CBS(S)C4.Inbreeding depression was lower for S1 lines from each of the advanced synthetics than for those of the corresponding original and was lowest for the S1 lines from SSS(HT)C7. Inbreeding depressions were 39.1 and 27.8%, respectively, for S1 lines from SSS and SSS(HT)C7, and 38.3 and 32.5%, respectively, for S1 lines from CBS and CBS(S)C4. S1 lines from SSS(HT)C7 averaged 9.3% higher in yield than those from SSS, although the range of yields was less at both extremes for lines from the advanced population. S1 lines from CBS(S)C4 averaged 27.2% higher than those from CBS with a comparable range of yields.SSS(HT)C7 yielded slightly less than SSS. CBS(S)C4 yielded approximately 19% more than CBS. In all populations the maximum S1 yield approximated that of the parental source. Two S1 lines from CBS(S)C4 were comparable in yield to that of a double‐cross hybrid check variety. One effective means of increasing inbred line yields appears to be increasing the yields of parental source populations.

Governor Berkeley and King Philip's War

V IRGINIA and Massachusetts had little official contact with each other in the seventeenth century.1 However, a good deal of trade between the two colonies was carried on, consisting mostly in the exchange of Virginia corn and tobacco for New England fish and other commodities.2 The trade was often triangular via the West Indies. Despite the lack of official contact, the leaders of each colony followed developments in the other with great interest and no little partiality. Governor Winthrop noted in his journal for May 20, 1644, a ship from Virginia had brought news of the great massacre there in which perhaps 500 English were killed. It was reported an Indian confessed that they did it because they saw the English took up all their lands from them, and would drive them out of the country.... Winthrop commented soberly