Corn Plant Population Research Articles

PERKEMBANGAN Spodoptera frugiperda J.E Smith PADA TANAMAN JAGUNG MANIS (Zea mays L. Saccharata)

This study was conducted to determine the relationship between sweet corn plant phenology and population development and the attack of Spodoptera frugiperda. The research was carried out at the Research Farm and at the Laboratory of Plant Pests, Faculty of Agriculture, Jambi University. The study was conducted on an area of 500 m2 containing 28 plant plots. The sample plants consisted of 4 plots determined systematically. In each sample plot, all plants were used as sample. plants to calculate the percentage of attacked plants, and the percentage of attacked cobs. S. frugiperda population observations were carried out directly on leaves, stems, flowers and cobs. If there were S. frugiperda faeces on the shoots, stems, and cobs, destructive observations were made where the plant parts were opened, to determine the presence of S. frugiperda in them. The data obtained were tabulated and arranged in the form of tables and figures, then explained descriptively. The results showed that: the population of S. frugiperda in each growth phase continued to increase, the highest population of S. frugiperda was found in the R6 phase or in the physiological ripening phase, which was as many as 21 heads per 12 corn plants; the percentage of attacks of S. frugiperda in each phase continues to increase, the highest percentage of attacks is in phase R6, which is 78.72%; the attack of S. frugiperda on cobs began to be seen in the R2-R5 phase and was highest in the R6 phase, which was 68.57%. It is necessary to find the right way to control S. frugiferda.

Is Strip‐till a Useful Soil Management Tool for Wisconsin Corn and Soybean Production?

Alleviation of cold, wet, and compacted soils is of great importance for earlier planting that can lead to improved yield in short growing season environments. Strip‐till adoption in corn has increased as a sustainable means to improve soil conditions and yield; however, the response of soybean to strip‐till has been less consistent. The objectives of this research were to (1) quantify the effect of strip‐till, row spacing (soybean only), crop rotation (corn only), fertilizer placement, and in‐furrow fungicide on corn and soybean plant population, canopy coverage, and grain or seed yield; (2) evaluate strip‐till, row spacing, fertilizer placement, and in‐furrow fungicide on soil temperature and penetration resistance; and (3) determine best management recommendations for strip‐till use in Wisconsin corn and soybean production systems. Earn 0.5 CEUs in Soil & Water Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/798.

Strip‐till, other management strategies, and their interactive effects on corn grain and soybean seed yield

AbstractAlleviation of cold, wet, compacted soils is of great importance for earlier planting that can lead to improved yield in short growing season environments. Strip‐till adoption in corn (Zea mays L.) has increased as a sustainable means to improve soil conditions and yield; however, the response of soybean [Glycine max (L.) Merr.] to strip‐till has been less consistent. This study aims to: (i) quantify the effect of strip‐till, row spacing (soybean only), crop rotation (corn only), fertilizer placement, and in‐furrow fungicide application on corn and soybean plant population, canopy coverage, and grain or seed yield, (ii) evaluate the effect of strip‐till on soil temperature and penetration resistance, and (iii) determine best management recommendations for strip‐till use in Wisconsin corn and soybean production systems. A small‐plot experiment was conducted in Arlington, WI, during the 2016, 2017, and 2018 growing seasons. In soybean, banded fertilizer resulted in 0.3 Mg ha–1 (6.5%) greater yield than surface‐applied fertilizer. Greatest soybean seed yield was obtained by combining strip‐till, in‐furrow fungicide, and 38‐cm row spacing. In corn, strip‐till yielded 0.8 Mg ha–1 (5.7%) greater than no‐till and banded fertilizer yielded 0.7 Mg ha–1 (4.9%) higher than surface‐applied fertilizer. In soybean, yields in strip‐till were generally equivalent to no‐till and yield benefits associated with strip‐till were dependent on other management factors. In corn, banded fertilizer, strip‐till, and the corn in corn–soybean (CS) rotation with in‐furrow fungicide resulted in greatest yields. Strip‐till was a beneficial soil management tool for improving grain yield in Wisconsin.

Can Management Practices Enhance Corn Productivity in a Rye Cover Crop System?

Cereal rye (Secale cereale L.) cover crops (RCC) have good potential to take up residual NO3 between grain crops and reduce loss to surface waters. However, studies in Iowa have shown a 6% corn (Zea mays L.) yield reduction in no‐till when grown following a RCC. The objective of this research was to study tillage and starter N agronomic practices that have potential to improve corn yield in a RCC system. This study was conducted at four sites from 2014–2016 with corn grown in rotation with soybean [Glycine max. (L.) Merr.]. Treatments included rye aerial broadcast into soybean before leaf drop and no RCC, tillage or no‐till, and starter N fertilizer (34 kg N ha−1) or no starter. The main fertilizer N was sidedressed. The aerial rye sowing, especially with dry fall conditions and planned RCC termination in the spring at 15–20 cm height, resulted in non‐uniform RCC stand with low biomass and N content (range 6–36 kg N ha−1). However, the profile soil NO3–N at rye termination was decreased, approximately the same amount as the RCC aboveground N content. The V6 stage corn height and V10 stage canopy sensing indexes increased with tillage and starter. Overall, corn yield was reduced with the RCC (0.2 Mg ha−1), tillage increased yield (3%), but starter N did not increase yield despite consistent increased early corn growth. If soil erosion potential is low, springtime tillage would be a practice to help improve corn early growth and yield in a RCC system.Core Ideas A cereal rye cover crop preceding corn can result in reduced grain yield. Rye cover crop did not affect corn plant population. Starter N improved early corn growth but not grain yield. Corn yield was 1.6% reduced with the rye cover crop, but tillage improved yield by 3%.

Enhanced Efficiency Liquid Nitrogen Fertilizer Management for Corn Production

Claypan soils have a high potential for N loss, which can lower corn (Zea maysL.) yields. Field research was conducted from 2011 to 2013 in Northeast Missouri to determine corn yield, plant population, and grain quality response to N application timings (fall vs. spring) and five N sources/placements at two different N rates (84 and 168 kg·N·ha−1) on a poorly drained claypan soil. The five N source/placement systems were no-till (NT)/surface broadcast urea ammonium nitrate (UAN) (Surface UAN) or strip-till (ST)/deep banded UAN (deep UAN), NT/surface broadcast UAN plus Nitamin Nfusion (surface NF) or ST/deep banded UAN plus Nitamin Nfusion (deep NF), and ST/deep banded anhydrous ammonia (AA) (deep AA). The field trial was a split-plot randomized complete block design with four replications. Deep UAN with a fall N application produced the highest grain yield (8.12 to 9.12 Mg·ha−1) at 84 and 168 kg·N·ha−1, but it was less effective with a spring application in 2011. Fall deep AA produced the lowest grain yields (5.97 and 6.8 Mg·ha−1) in 2013 at 84 and 168 kg·N·ha−1potentially due to wet soil conditions at the time of application. Warmer and wetter soil conditions during April-May of 2013 resulted in relatively higher grain yields compared to cooler and drier soil conditions in 2011 with all spring-applied N source/placement treatments. Extreme drought in the 2012 growing season resulted in poor corn growth. Farmers may need to consider fall N applications on claypan soils because spring N application might be riskier since corn grain yield was generally greater than or equal to spring-applied treatments.

Effects of agronomic factors on yield and quality of whole corn plants and the impact of feeding high concentrations of corn silage in diets containing distillers grains to finishing cattle.

Corn plants were sampled over 2 consecutive years to assess the effects of corn hybrid maturity class, plant population, and harvest time on whole corn plant quality and yield in Nebraska. A finishing experiment evaluated the substitution of corn with corn silage in diets with corn modified distillers grains with solubles (MDGS). The first 2 harvest dates were at the mid- and late-silage harvest times whereas the final harvest was at the grain harvest stage of plant maturity. Whole plant yields increased as harvest time progressed (yr 1 quadratic P < 0.01; yr 2 linear P < 0.01). However, differences in TDN concentration in both years were quite minimal across harvest time, because grain percentage increased but residue NDF in-situ disappearance decreased as harvest time was delayed. In the finishing experiment, as corn silage inclusion increased from 15 to 55% (DM basis) by replacing dry rolled and high moisture corn grain with corn silage in diets containing 40% MDGS, DMI, ADG, and G:F linearly decreased (P ≤ 0.01), with the steers on the 15% corn silage treatment being 1.5%, 5.0%, and 7.7% more efficient than steers on treatments containing 30, 45, and 55% corn silage, respectively. Calculated dietary NEm and NEg decreased linearly as corn silage inclusion increased indicating that net energy values were greater for corn grain than for corn silage. In addition, dressing percentage decreased linearly (P < 0.01) as silage inclusion increased suggesting more fill as silage inclusion increases in diets. Cattle fed greater than 15% corn silage in finishing diets based on corn grain will gain slower and be slightly less efficient and likely require increased days to market at similar carcass fatness and size. When 30% silage was fed with 65% MDGS, DMI, and ADG were decreased (P < 0.01) compared to feeding 30% silage with 40% MDGS suggesting some benefit to including a proportion of corn in the diet. Conversely, when 45% silage was fed with 40% MDGS, ADG, and G:F were greater (P < 0.04) than when 45% silage was fed with just grain implying a greater energy value for MDGS than for corn grain. Substituting corn silage for corn grain in finishing diets decreased ADG and G:F which would increase days to finish to an equal carcass weight; however, in this experiment, increasing corn silage levels with MDGS present reduced carcass fat thickness without significantly decreasing marbling score.

Green Manure Comparison between Winter Wheat and Corn: Weeds, Yields, and Economics

Red clover (Trifolium pratense L.) and hairy vetch (Vicia villosa Roth) are leguminous crops (“green manure” hereafter), widely studied for their N2‐fixing contributions to cropping systems. Under certain circumstances they can provide weed control in cash crops. This study compared weed control, crop yields, herbicide use, and economic performance of these green manures in a no‐till winter cereal–green manure–corn (Zea mays L.) silage cropping sequence in central Pennsylvania. Red clover was interseeded into winter wheat (Triticum aestivum L.) or rye (Secale cereale L.), while hairy vetch and triticale (X Triticosecale) were planted after winter cereal harvest. Compared to hairy vetch, red clover provided continuous soil cover between the winter cereal and corn and two herbicide applications could not be applied (one in wheat and one prior to seeding hairy vetch) to the red clover, reducing herbicide active ingredient use by 28%. Weed infestation in wheat and corn did not differ between green manure systems, but corn yield following red clover averaged 3320 kg ha−1more, and 2012 wheat yield was 180 kg ha−1 greater in the red clover sequence. Corn after hairy vetch–triticale had lower corn plant population in 2012–2013. Yield differences in corn in 2012 probably resulted from population differences. Primarily because of red clover forage value, the red clover system resulted in greater net returns to management by US$1360 ha−1, and even without the forage harvest, the red clover system would have been more profitable due to lower production costs.Core Ideas As a green manure, red clover provided multiple benefits over hairy vetch and triticale. Red clover underseeded in winter grain, produced continuous cover, forage, and higher corn yield. Compared to hairy vetch and triticale, red clover controlled weeds with less herbicide. Red clover was more profitable than hairy vetch.

Improvement of a ground-LiDAR-based corn plant population and spacing measurement system

The variability of corn plant location and within-row spacing has been demonstrated to have a significant correlation with grain and biomass yield. They are included in many yield prediction models which are used to guide mid-season variable-rate fertilizer applications. A prototype sensing system was developed to automatically measure corn plant location and spacing on-the-go based on ground LiDAR technology. The system travelled along crop rows with a ground LiDAR sensor scanning at the bottom section of each corn plant. The possibility of corn stalk identification was increased because each stalk appeared in multiple scans from various view angles of the sensor. The first version of the prototyping system was developed earlier and resulted in a relatively low detecting accuracy. In this paper, an improved version of the prototyping system was presented with substantial additional field evaluation results. The system was improved in terms of the data acquisition platform and the data processing algorithms, specifically, the scan registration and stalk recognition procedures to reduce the misidentification errors. Additional field evaluation was conducted on 200 plants at their V8 growth stage. A total plant counting error of 5.5% and a 1.9cm of root-mean-squared error (RMSE) in spacing measurement were achieved between the sensor measurements and the manually measured ground truth data. The new data processing algorithm was also tested on the data collected with the first version system. The false positive plant counting error was reduced from 24.0% with the first version system to 14.0% with the improved algorithms.

Winter Annual Weed Management and Nitrogen Rate Effects on Corn Yield

Management of winter annual weeds (WAWs) can affect soil N availability and corn (Zea mays L.) production under no‐till systems. The objective of this study was to evaluate the effect of delaying WAW herbicide applications on N availability and grain yield for no‐till corn following soybean [Glycine max (L.) Merr.]. Field research was conducted in 2010 and 2011 at 14 sites with naturally‐occurring populations of WAWs in eastern Kansas. A factorial arrangement of three herbicide application dates (November–March, April, and May) and five N rates (0, 17, 34, 67, and 135 kg N ha–1) were used to evaluate the interaction between weed and N response. Corn plant population, soil nitrate‐N, early corn N uptake, chlorophyll meter (CM) readings at silking, and grain yield were measured. Analysis across site‐years, no significant interaction occurred between herbicide application date and N rate for variables measured. Delaying herbicide application until April significantly reduced early corn N uptake by 52 mg N plant–1, CM readings at silking by 3.4%, and grain yield by 0.48 Mg ha–1 across site‐years. Using the N fertilizer equivalence values (based on CM readings and grain yield), an estimated additional 16 to 17 kg N ha–1 was needed if herbicide application was delayed until April. Producers can increase corn N uptake and grain yield for rainfed no‐till corn following soybeans in eastern Kansas by applying herbicides on WAWs before April.

Corn yield response to polymer and non-coated urea placement and timings

Poorly drained claypan soils can increase the importance of tillage and N management for corn (Zea mays L.) production. Field research in 2008, 2009 and 2010 (high rainfall years) near Novelty, MO (40° 1' N, 92° 11' W) sought to determine the effect of polymer-coated urea (PCU) placement [strip-tillage (ST) deep banded and no-till (NT) broadcast] and application timing (fall, early preplant and preplant) on red clover (Trifolium pratense L.) biomass and corn response compared to non-coated urea (NCU) and anhydrous ammonia (AA) in the presence and absence of nitrapyrin a nitrification inhibitor. Strip-tillage reduced clover dry weights 20% in 2008 and 2009 and early preplant ST reduced dry weights 40 to 45% in 2010 compared to NT. Corn plant population was 8,100 to 8,400 plants ha -1 greater with ST compared to NT. Preplant applications of AA plus nitrapyrin, AA, ST placement of PCU and NCU increased grain yields 1 to 1.2 Mg ha -1 compared to fall applications of these fertilizer sources. Fall and preplant ST placement of PCU increased grain yields 1.2 Mg ha -1 compared to NCU. Strip-till placement of PCU and NCU increased yields 2.1 to 3.2 Mg ha -1 over broadcast applications of these fertilizer sources. Strip-till placement of PCU synergistically increased yield over NCU and broadcast applications of PCU or NCU due to increased stands and possibly due to better plant utilization of the banded N fertilizer utility.

Optimization of corn plant population according to management zones in Southern Brazil

Precision agriculture relies on site-specific interventions determined by the spatial variability of factors driving plant growth. The main objective of this study was to assess the efficiency of variable-rate seeding of corn (Zea mays L.) with delineated management zones. This study involved two experiments carried out in Nao-Me-Toque, Rio Grande do Sul, Brazil. For the first experiment, carried out in 2009/2010, management zones were delineated by the farmer’s knowledge of the crop field. The field was split into low (LZ), medium (MZ) and high (HZ) crop performance zones. In the second experiment, carried out in 2010/2011, management zones were delineated by overlaying standardized yield data from nine crop seasons (seven of soybean and two of corn). The experiment was carried out with a randomized block design with three management zones and five corn seeding rates ranging from 50 000 to 90 000 seeds per ha−1. The soil was a Rhodic Hapludox with a subtropical climate. Optimization of the corn plant population within the field increased grain yield compared to the reference plant population (70 000 plants ha−1). Yield increases in the LZ, due to corn plant population reduction in relation to the target population, were 1.20 and 1.90 Mg ha−1 for first and second experiments, respectively. This resulted in economic gains of 19.8 and 28.7 %, respectively. Yield increases in the HZ were 0.89 and 0.94 Mg ha−1, respectively, and were due to an increase in plant population in relation to the target population. This resulted in economic gains of 5.6 and 6.6 % for the first and second experiments, respectively. In the MZ, the adjustment of the target plant population was not necessary. Optimizing corn population according to management zones is a promising tool for precision agriculture in Southern Brazil.

Rendimento do milho em diferentes condições físicas de solo e quantidade de resíduo na ausência ou na presença de irrigação

Visando avaliar o efeito do tráfego de máquinas, da profundidade de atuação da haste sulcadora de adubo e da quantidade de resíduos presentes na superfície do solo sobre o desempenho do milho, com e sem irrigação, foi conduzido um experimento, em semeadura direta, sobre um Argissolo Vermelho Distrófico. O delineamento foi de blocos casualizados (DBC), com 36 parcelas, sendo 18 irrigadas e 18 sem irrigação. Os tratamentos consistiram de seis doses de resíduos de aveia preta consorciada com ervilhaca (0, 2, 4, 5, 6 e 8Mg ha-1), duas profundidades teóricas de atuação da haste sulcadora de adubo da semeadora (6 e 12cm) e duas condições de tráfego de máquinas (trator e colhedora), sendo enquadrados numa análise trifatorial com três repetições. A semeadura do milho foi realizada em 10 de dezembro de 2005, com densidade de 62.000 sementes por hectare. A adubação usada foi de 400kg ha-1 da formulação NPK 5-20-20 e duas aplicações de nitrogênio, totalizando 180kg ha-1. Foram avaliados o rendimento de grãos, a população e a matéria seca de raízes. Tanto a população de plantas, quanto o rendimento de grãos do milho, foram influenciados pela presença ou não de irrigação. A profundidade de atuação das hastes sulcadoras não interferiu em nenhumas das variáveis avaliadas no milho. A condição de tráfego de rodado afetou a produtividade e a população de plantas.

Impact of Irrigation and Hail on Palmer Amaranth (Amaranthus Palmeri) in Corn

In 2005 a hailstorm struck a long-term dose–response study of irrigation requirements and corn plant populations. This misfortune occurred again in 2006 at approximately the same growth stage. Therefore, the objectives of the studies were redirected to measure the impact of actual hail events on corn leaf area index (LAI) and the competitive interaction of escaped Palmer amaranth populations induced by hail across different levels of irrigation and corn populations. In 2005, the study treatment with the lowest corn population and level of irrigation had twice the Palmer amaranth biomass (PABM) at corn harvest compared with the highest corn population and irrigation level. Corn LAI produced simple linear models that predicted both corn grain yield and PABM. In 2007, the nonhail year, PABM was depressed 4- to 15-fold compared with hail years. PABM declined linearly from 417 kg/ha at the lowest level of irrigation and corn population to 48 kg/ha at the highest level of irrigation and corn plant population. Although economic return per increment of irrigation declined in both hail years, the trends in economic returns were still positive. This suggests that a producer with similar conditions should continue to irrigate even though his or her rate of economic return is reduced.

Self‐Seeded Cereal Cover Crop Effects on Interspecific Competition with Corn

Perpetuating cereal cover crops through self‐seeding may increase adoption by reducing risk and cost. Winter rye (Secale cereale L.), wheat (Triticum aestivum L.), and triticale (× Triticosecale Wittmack) were used to develop self‐seeding cover crop systems in a soybean [Glycine max (L.) Merr.]–corn (Zea mays L.) rotation. Cereal cover crops were planted in varying row spacing configurations and managed chemically and mechanically to achieve different levels of resource utilization in time and space. The objective of this study was to quantify interspecific competition of self‐seeded winter cereal cover crops growing concurrently with corn. Total weed density responded more to environment than cover crop treatment, with 12.0 and 2.2 weeds m−2 in 2005 and 2006. Averaged across species, cover crop treatments lowered corn grain yield 5 to 22% compared with a no cover crop check. The most promising treatment lowered corn grain yield 7 and 11%, which is in the range for previously reported yield reduction using rye cover crops when rye was killed at or immediately after planting in a corn–soybean rotation. Cover crop regrowth intercepted &lt;9% of photosynthetically active radiation (PAR) during early growth of corn. Combinations of lower corn plant population density and kernel density in cover crop treatments appear most responsible for the yield reduction. Additional research should focus on reducing interspecific competition during vegetative growth in corn when sink size is being determined.

In-Row Subsoil Tillage and Planting Depth Influence on Corn Plant Population and Yield on Sandy-Textured Mid-Atlantic Coastal Plain Soils

In-Row Subsoil Tillage and Planting Depth Influence on Corn Plant Population and Yield on Sandy-Textured Mid-Atlantic Coastal Plain Soils

Real-Time Crop Row Image Reconstruction for Automatic Emerged Corn Plant Spacing Measurement

In-field variations in corn plant spacing and population can lead to significant yield differences. To minimize these variations, seeds should be placed at a uniform spacing during planting. Since the ability to achieve this uniformity is directly related to planter performance, intensive field evaluations are vitally important prior to design of new planters and currently the designers have to rely on manually collected data that is very time consuming and subject to human errors. A machine vision-based emerged crop sensing system (ECSS) was developed to automate corn plant spacing measurement at early growth stages for planter design and testing engineers. This article documents the first part of the ECSS development, which was the real-time video frame mosaicking for crop row image reconstruction. Specifically, the mosaicking algorithm was based on a normalized correlation measure and was optimized to reduce the computational time and enhance the frame connection accuracy. This mosaicking algorithm was capable of reconstructing crop row images in real-time while the sampling platform was traveling at a velocity up to 1.21 m s-1 (2.73 mph). The mosaicking accuracy of the ECSS was evaluated over three 40 to 50 m long crop rows. The ECSS achieved a mean distance measurement error ratio of -0.11% with a standard deviation of 0.74%.

SHAPE AND SIZE ANALYSIS OF CORN PLANT CANOPIES FOR PLANT POPULATION AND SPACING SENSING

An effective corn plant population and spacing sensing system may provide a key layer of field variabilityinformation useful for crop management. An algorithm was developed to count corn plants and to estimate plant location andintra-row spacing in segmented images of 6.1-m (20-ft) long row sections. Images were scanned to detect and determine theboundaries of top projected corn plant canopy objects using a chain code methodology. Plant objects were fused togetherbased on a multi-step process that took into account the spatial structure of the crop row. Position, roundness, and area ofplant canopies were used to distinguish between corn plants and weeds. Estimates of plant counts in row sections werecompared with manual counts across three growth stages, three populations, and three tillage treatments. Overall, the systemestimated the number of plants with an RMSE of 1.49 plants per row section, which corresponds to 6.2% RMSE or 3210plants/ha (1300 plants/acre). No evidence of significant differences in mean plant spacing estimates was detected althoughsignificant, albeit small, increases in spacing variance were detected. These results demonstrate the importance of canopyshape and size analysis in the implementation of a machine vision plant population and intra-row spacing sensing system.

Cover Crop Management and Weed Suppression in No-tillage Sweet Corn Production

Cover crops combined with conservation tillage practices can minimize chemical inputs and improve soil quality, soil water-holding capacity, weed suppression and crop yields. No-tillage production of sweet corn (Zea mays var. `Silver Queen') was studied for 2 years at the USDA Beltsville Agricultural Research Center, Md., to determine cover crop management practices that maximize yield and suppress weeds. Cover crop treatments were hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and hairy vetch mixture, and bare soil (no cover crop). There were three cover crop killing methods: mowing, rolling or contact herbicide paraquat. All plots were treated with or without atrazine and metolachlor after planting. There was a 23% reduction in sweet corn plant population in the rye-hairy vetch mixture compared to bare soil. Averaged over both years, sweet corn yield in hairy vetch treatments was 43% greater than in bare soil, whereas yield in the rye-hairy vetch mixture was 30% greater than in bare soil. There were no significant main effects of kill method or significant interactions between kill method and cover crop on yield. Sweet corn yields were not different for hairy vetch or rye-hairy vetch treatments with or without atrazine and metolachlor. However, yield in bare soil without the herbicides atrazine and metolachor were reduced by 63% compared to bare soil with these herbicides. When no atrazine and metolachlor were applied, weed biomass was reduced in cover crops compared to the bare soil. Regression analysis showed greater yield loss per unit of weed biomass for bare soil than for the vetch or rye-hairy vetch mixture. This analysis suggests that cover crops increased sweet corn yield in the absence of atrazine and metolachlor not only by reducing weed biomass, but also by increasing the competitiveness of corn to weeds at any given biomass.

Weed Management in Strip Tillage Corn

Field studies were conducted in 2000 and 2001 to determine if differences exist in weed emergence patterns, weed control, corn (Zea mays L.) plant population, and grain yield in strip tillage, conventional tillage, and no‐tillage production. Weed emergence peaked at 2 and 4 wk after planting (WAP) in 2000 and 2001, respectively. Weed emergence at 2 WAP in 2000 was greater in conventional tillage compared with no‐tillage and strip tillage. Tillage system did not affect total weed species emergence in 2001. In both years, lower control of giant foxtail (Setaria faberi Herrm.) and common waterhemp (Amaranthus rudis Sauer) occurred following acetochlor {[2‐chloro‐N‐(ethoxymethyl)‐N‐(2‐ethyl‐6‐methylphenyl)acetamide]} plus atrazine {[6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine]} applied pre‐emergence in no‐tillage compared with conventional tillage. Control of common waterhemp in 2001 and giant foxtail in both years was similar with glyphosate [N‐(phosphonomethyl)glycine] applied postemergence regardless of tillage system. Corn population was greater in conventional tillage compared with no‐tillage in 2000 and greater than the population in no‐tillage and strip tillage in 2001. When averaged across weed management strategies, corn yield was greatest in strip tillage in 2000 and conventional tillage in 2001.

A genetic-algorithm-based selective principal component analysis (ga-spca) method for high-dimensional data feature extraction

A genetic-algorithm-based selective principal component analysis (GA-SPCA) method is proposed and tested using hyperspectral remote sensing data and ground reference data collected within an agricultural field. The proposed method uses a global optimizer, the genetic algorithms, to select a subset of the original image bands, which first reduces the data dimension. A principal component transformation is subsequently applied to the selected bands. By extracting features from the resulting eigenimage, the remote sensing data, originally high in dimension, will be further reduced to a feature space with one to several principal component bands. Subsequent image processing on the reduced feature space can thus be performed with improved accuracy. Experiments were conducted using three sets of ground reference data: corn chlorophyll content, corn plant population, and various corn hybrids. The results showed that with GA-SPCA, the number of original bands used for principal component analysis (PCA) could be reduced to 17, 26, and 25 from a 60-band hyperspectral image, respectively. In all cases, the correlation coefficients between image and ground reference data were greater when using GA-SPCA than that for PCA results with all original bands. This indicates that bands with no contribution to a specific application were removed prior to PCA. The variance related to a specific application within the image was transformed with more emphasis by using bands sensitive to that application. The selected bands can also provide useful information for future imaging sensor development.