Corn Rows Research Articles

Agricultural land use and hydrology affect variability of shallow groundwater nitrate concentration in South Florida

AbstractSouth Florida's Miami‐Dade agricultural area is located between two protected natural areas, the Biscayne and Everglades National Parks, subject to the costliest environmental restoration project in history. Agriculture, an important economic activity in the region, competes for land and water resources with the restoration efforts and Miami's urban sprawl. The objective of this study, understanding water quality interactions between agricultural land use and the shallow regional aquifer, is critical to the reduction of agriculture's potentially negative impacts. A study was conducted in a 4‐ha square field containing 0·9 ha of corn surrounded by fallow land. The crop rows were oriented NW–SE along the dominant groundwater flow in the area. A network of 18 monitoring wells was distributed across the field. Shallow groundwater nitrate–nitrogen concentration [N‐NO3−] was analyzed on samples collected from the wells biweekly for 3 years. Detailed hydrological (water table elevation [WTE] at each well, groundwater flow direction [GwFD], rainfall) and crop (irrigation, fertilization, calendar) data were also recorded in situ. Flow direction is locally affected by seasonal regional drainage through canal management exercised by the local water authority. The data set was analyzed by dynamic factor analysis (DFA), a specialized time series statistical technique only recently applied in hydrology. In a first step, the observed nitrate variation was successfully described by five common trends representing the unexplained variability. By including the measured hydrological series as explanatory variables the trends were reduced to only three. The analysis yields a quantification of the effects of hydrological factors over local groundwater nitrate concentration. Furthermore, a spatial structure across the field, matching land use, was found in the five remaining common trends whereby the groundwater [N‐NO3−] in wells within the corn rows could be generally separated from those in fallow land NW and SE of the crop strip. Fertilization, masked by soil/water/plant‐delayed processes, had no discernible effect on groundwater nitrate levels. Copyright © 2006 John Wiley & Sons, Ltd.

Traditional Life on Straight Creek Eighty Years Ago

RECIPES AND RECOLLECTIONS Traditional Life on Straight Creek Eighty Years Ago Sidney Saylor Farr The Industrial Revolution brought the need for mineral resources, and mining industries came in and tore up the Kentucky and West Virginia Mountains to extract the wealth underneath. Engineers like Mary Lee Settle's father, who arrived in Bell County in the second decade of the 20th Century, were among those who came to the area. This brought the outside world headlong into some parts of the mountains. Meanwhile, other isolated pockets remained, and people like my family continued just as our forefathers had done before us. By the time my father was a young man, most of the agricultural fields in the area were worn out, and local people had to keep clearing new ground for fields to plant. Father courted and married Mama in 1930. She was from Laurel Fork in Leslie County, Kentucky. He built a log cabin just over the hill from Grandpa on Coon Branch of Stoney Fork which ran into Straight Creek which flowed into the Cumberland River at Pineville, about fifteen miles away. Two years later I was born in that cabin on Coon Branch. I have read about how 1932 became known as the year of the drought. People were starving because of the scarcity of crops and wild game. The first charity my family ever accepted was provided by the Red Cross which came in with food to help during the drought. Wild game was very scarce, but still Father brought in a few squirrels and groundhogs and managed to raise a few hogs, which were fattened on the scant supply of woods' mast. On Stoney Fork, each little homestead had its cornfield, its patch of sorghum cane, and its beehives. Down the creek was a gristmill where corn was ground into meal. Hidden in a hollow was a moonshine still, where corn was made into whiskey. Pine Mountain rises from the south side of Straight Creek, one hundred miles long, running through three counties in Kentucky and on into Tennessee. It is filled with limestone caves and covered with scrub trees. A footpath ran up in front of our log cabin across the mountain to the Cumberland River side. Here the railroad played a 104 steei counterpoint to the river, as long trains filled with Harlan County coal shuttled along to Pineville and points north and east. I am the oldest of ten children. Father worked in the timber woods when he could. We ate what we grew on the place or could glean from the hillsides. Just about everything was made by hand, and we had little contact with people outside the region. In southeastern Kentucky almost everyone lived in poverty. If it had not been for the small farms and gardens, domestic animals, and wild game brought in from the hills, our people would have starved out long ago. But we planted corn and raised gardens, chickens, and livestock. We picked fruit and berries, canned and preserved as much food as we could for winter and, in general, made do with what we had. Fortunately, the skills possessed by pioneers have been taught, father to son, mama to daughter, down through the generations, and there is still knowledge of how to raise gardens, tend small orchards, and plant and raise corn on hillsides so steep it was difficult to stand upright in rows of corn. Both my parents, descendents of the pioneers who first came through nearby Cumberland Gap, dug ginseng and other roots, which they dried and sold by the pound in the late fall. For a number of years Daddy made and sold moonshine whiskey. He was skilled at castrating domestic animals, and the neighbors hired him to perform this service for their hogs and bull calves. With money coming in small payments for these services, and for the roots and herbs, the dozen or so eggs sold each week, the occasional gallon of milk or blackberries sold or exchanged for groceries, we managed to pay for food products which did not grow in the hills and for shoes and other pieces of clothing. In the mountains many traditions introduced by the...

Influence of population density, row spacing and hybrid on forage corn yield and nutritive value in a cool-season environment

Increasing yield for silage and grazing in cool, short-season areas may be possible by planting corn (Zea mays L.) at high population densities and at narrow row spacing. The objective was to determine how population density (75 000, 100 000, and 125 000 plants ha-1) and row spacing (standard: 76 cm and narrow: 38 cm) affected whole-plant yield, yield-related parameters, and nutritive value of two corn hybrids grown at Brooks and Lacombe, Alberta during 2 yr. The hybrids (Pioneer 39F45 and 39N03) were rated at 2000 Ontario corn heat units (CHU). Trial, hybrid, population density and row spacing interacted to influence whole-plant yield. Population density had a greater impact on whole-plant yield than row spacing and hybrid choice. Generally, yield leveled off at 100 000 plants ha-1 when the interaction of all effects was considered. Leaf area index (LAI) and whole-plant yield at this density were 2.68 and 12.0 Mg ha-1, respectively. Narrow compared with standard row spacing had positive effects on whole-plant yield of one hybrid, but not the other and improved LAI at 75 000 plants ha-1, but not at the other plant densities. Increasing plant density and reducing row spacing had only minor effects on whole-plant nutritive value. Growing corn in narrow rows to accommodate prevalent planting equipment should have no adverse effects on whole-plant corn production in short-season areas of Canada. However, when considering changes in corn management to maximize whole-plant yield narrow row spacing is not as important as achieving a plant density of approximately 100 000 plants ha-1. Key words: Corn, Zea mays L., nutritive value, population density, row width, silage yield

Effects of green manure use on sweet corn root length density under reduced tillage conditions

A green manure (GM) is a crop grown primarily as a nutrient source and soil amendment for subsequent crops. In environments such as Florida, combined use of GM and reduced tillage may improve soil water and nutrient retention and reduce potential groundwater pollution. In the first 3 years of a long-term experiment, use of GM in a reduced-tillage system on a sandy Florida soil benefited the season-long growth of sweet corn (Zea maysL. var. Rugosa) much more than final ear yields. To help understand these patterns, we evaluated response of sweet corn roots when in rotation with GM of sunn hemp (Crotalaria junceaL.; summer) and cahaba white vetch (Vicia sativaL.; winter 2002–2003) and a multi-species mixture of hairy vetch (V. villosaRoth.) and cereal rye (Secale cerealeL.; winter 2003–2004). Treatments included sweet corn with combinations of 0 or 133 kg chemical N ha−1(as NH4NO3) and with or without GM. A highly fertilized treatment (267 kg chemical N ha−1) without GM was also included. Soil cores were sampled from three depths (0–15, 15–30 and 30–60 cm) both between and within corn rows. Data from two experiments showed that use of GM increased sampled corn root length density (RLD) by 44–54%, although only within the upper 15 cm of soil in one of the two experiments. Corn following GM plus 133 kg chemical N ha−1produced up to 44% greater RLD than corn with 267 kg chemical N ha−1. Sampled RLD decreased with distance away from corn plants (from in-row to between-row positions, and from shallow to deeper depth), with roughly 85–95% of sampled RLD existing in the top 30 cm of soil across all treatments. During the 2004 experiment, we found that broadcast, as opposed to banded (placed along corn row only), chemical N application resulted in more even distribution of corn RLD between in-row and between-row positions during late-season without regard to GM crop. Although GM permitted optimal sweet corn growth with a 50% reduction in chemical N application, ear fill during the final 1–2 weeks before harvest may have been reduced in GM treatments. GM effects on the amount and spatial distribution of sweet corn RLD may help explain these trends. Provision of greater N from GM residues and/or altered distribution of supplementary chemical N and irrigation may be required to achieve greater ear yield benefit from GM.

Effect of plant row spacing and herbicide use on weed aboveground biomass and corn grain yield

The use of narrow plant spacing in corn (Zea mays) has been suggested as a technological alternative to obtain grain yield increases, due to a better use of resources. The regular pattern could diminish intraspecific competition while favoring interspecific competition with weeds. The objective of this study was to analyze the effect of corn row spacing on weed aboveground biomass and corn grain yield. Field experiments were conducted during 2002/2003 and 2003/2004 growing seasons. Three corn hybrids with two-row width (0.70 and 0.35 m) were tested. A greater photosynthetic photon flux density (PPFD) interception with a lower weed aboveground dry matter in narrow row arrangement was obtained. Corn grain yield was greater in the narrow row arrangement than in the wide row spacing. This increase in grain yield was related to a better resource use that allows for a reduced interspecific competition. The use of reduced spatial arrangement appeared to be an interesting alternative to increase both the grain yield potential and corn suppressive ability against weeds in corn dryland production systems.

Annual weed competitiveness as affected by preemergence herbicide in corn

Competitiveness of weeds that survive a PRE herbicide application (escaped weeds) might be altered because of herbicide injury. As a result, potential crop yield loss may be reduced. Field experiments were conducted at Ashland Bottoms, KS, in 2001 and 2002 and at Rossville, KS, in 2002. The objectives were to quantify corn growth and yield response to Palmer amaranth or velvetleaf competition, with or without isoxaflutole (0.03 kg ha−1) or flumetsulam (0.04 kg ha−1) application, and to determine seed production of Palmer amaranth or velvetleaf as affected by PRE herbicide. Palmer amaranth and velvetleaf densities ranged from 0 to 6 and 0 to 32 plants m−1of corn row, respectively. At Ashland Bottoms in 2002, corn height at tasseling decreased with increasing Palmer amaranth (1.58 cm weed−1m−1) and velvetleaf (1.32 cm weed−1m−1) density when no herbicide was applied. With flumetsulam application, each increase in velvetleaf density reduced corn height by 0.4 cm. Escaped Palmer amaranth and velvetleaf were shorter than untreated plants at corn tasseling. At Rossville in 2002, Palmer amaranth that escaped isoxaflutole or flumetsulam application caused 13% corn yield loss (YL) at a density of 3 plants m−1. In contrast, corn YL from untreated Palmer amaranth at the same density was 30%. At Ashland Bottoms in 2002, velvetleaf that escaped flumetsulam caused 3% corn YL at a density of 3 plants m−1compared with 38% YL caused by untreated velvetleaf at the same density. Seed production of Palmer amaranth was independent of density or herbicide treatment, whereas production of velvetleaf seed increased with density, with or without flumetsulam. The study showed that corn YL from both Palmer amaranth and velvetleaf that escaped a PRE herbicide was less than from untreated weeds, but seed production by escaped weeds was similar to that of untreated weeds.

Growth, Yield, Quality, and Economics of Corn Silage under Different Row Spacings

Corn (Zea mays L.) silage in the northeastern USA yields more in narrow (0.38 m) than conventional (0.76 m) rows. Dairy producers, however, have considered converting from conventional to twin rows (0.19 m on 0.76 m centers) because twin rows are more compatible than narrow rows for herbicide application on glyphosate‐resistant corn. Two hybrids were planted in field‐scale studies in New York in 2003 and 2004 to evaluate growth, yield, quality, and economics of corn silage under conventional, narrow, and twin row production systems. Narrow rows had greater dry matter yield (17.6 Mg ha−1) than twin (17.2 Mg ha−1) and conventional rows (16.6 Mg ha−1). Row spacing did not affect in vitro true digestibility. Narrow and twin rows had greater fixed and variable costs associated with equipment requirements. Partial budget analyses indicated greater expected increases in annual profit with the conversion from conventional to narrow rows for 262 ($18 201) and 525 ha ($38 317) or to twin rows for 262 ($8246) and 525 ha ($17 584) of corn silage. The use of glyphosate‐resistant corn in twin rows may provide an advantage by delaying herbicide application until mid‐June, thereby increasing the probability of a timely first harvest of perennial forages. Dry matter content at harvest averaged 326 g kg−1 in narrow versus 314 g kg−1 in twin rows, increasing the probability of corn silage harvest before a fall frost. Dairy producers should consider economics and timely harvests when considering corn silage row‐spacing systems.

Response of Corn (Zea mays) and Weeds to Planting Pattern and Herbicide Use

ABSTRACT The use of narrow row arrangement in corn (Zea mays) has been suggested as a technological alternative to obtain grain yield increases through a better use of the resources. The regular pattern could diminish intraspecific competition while favouring interspecific competition with weeds. The objective of this study was to analyse the effect of corn planting pattern and herbicide application on (i) soil water content and photosynthetically active radiation (PAR) dynamics, (ii) below ground and above ground corn biomass and grain yield and (iii) weed suppressive ability of dryland corn sown at square and rectangular plant arrangement. Field experiments were conducted during the growing seasons 2002/03 and 2003/04. Three corn hybrids with two plant arrangement (rectangular: 0.70 × 0.20 m and square: 0.35 × 0.35 m) and herbicide (2.25 kg ai ha−1 of atrazine and 2.32 kg ai ha−1 of metolachlor) use compared with no herbicide use were tested. In the initial stages of the crop there was greater moisture content in the row of corn sowed at square planting pattern while a lower soil water content at maturity was observed. Conversely, between rows, the square plant arrangement registered lower soil water content during the growing cycle of the crop. This soil water profile was a consequence of the uniform corn below ground dry matter distribution. A greater PAR interception with a lower weed above ground dry matter was obtained in square plant arrangement. Corn grain yield was greater in the square-planting pattern than in the rectangular ones. This increase in grain yield was related to better resources use i.e. soil moisture and PAR interception while reduces the competition from weeds. The use of equidistant plant arrangement appeared as an interesting alternative to increase both the grain yield potential and the corn suppressive ability against weeds in dryland Argentinean production systems.

Evaluation of Corn (Zea mays L.) Yield-loss Estimations by WeedSOFT® in the North Central Region1

Field studies were conducted in 2000 and 2001 to evaluate corn yield-loss predictions generated by WeedSOFT, a computerized weed management decision aid. Conventional tillage practices were used to produce corn in 76-cm rows in Illinois, Indiana, Kansas, Michigan, Missouri, Nebraska, and Wisconsin. A total of 21 site-years from these seven states were evaluated in this study. At 4 wk after planting, weed densities and size, crop-growth stage, estimated weed-free yield, and environmental conditions at the time of application were entered into WeedSOFT to generate POST treatments ranked by percent maximum yield (PMY). POST treatments were chosen with yield losses ranging from 0 to 20%. Data were subjected to linear regression analysis by state and pooled over all states to determine the relationship between actual and predicted yield loss. A slope value equal to one implies perfect agreement between actual and predicted yield loss. Slope value estimates for Illinois and Missouri were equal to one. Actual yield losses were higher than the software predicted in Kansas and lower than predicted in Michigan, Nebraska, and Wisconsin. Slope value estimate from a data set containing all site years was equal to one. This research demonstrated that variability in yield-loss predictions occurred at sites that contained a high density of a single weed specie (>100/m2) regardless of its competitive index (CI); at sites with a predominant broadleaf weed with a CI greater than five, such as Palmer amaranth, giant ragweed, common sunflower, and common cocklebur; and at sites that experience moderate to severe drought stress.Nomenclature: common cocklebur, Xanthium strumarium L. #3 XANST; common lambsquarters, Chenopodium album L. # CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; common sunflower, Helianthus annuus L. # HELAN; common waterhemp, Amaranthus rudis Sauer. # AMATA; corn, Zea mays L. # ZEAMX; eastern black nightshade, Solanum ptycanthum Dun. # SOLPT; green foxtail, Setaria viridis (L.) Beauv. # SETVI; giant foxtail, Setaria faberi Herrm. # SETFA; giant ragweed, Ambrosia trifida L. # AMBTR; fall panicum, Panicum dichotomiflorum Michx. # PANDI; ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. # IPOHE; large crabgrass, Digitaria sanguinalis (L.) Scop. # DIGSA; morningglory spp., Ipomoea spp. # IPOSS; Palmer amaranth, Amaranthus palmeri S. Wats. # AMAPA; Pennsylvania smartweed, Polygonum pensylvanicum L. # POLPY; pitted morningglory, Ipomoea lacunosa L. # IPOLA; prickly sida, Sida spinosa L. # SIDSP; redroot pigweed, Amaranthus retroflexus L. # AMARE; velvetleaf, Abutilon theophrasti Medicus # ABUTH; Venice mallow, Hibiscus trionum L. # HIBTR.Additional index words: Bioeconomic model, decision support system, herbicide decision aid.Abbreviations: CI, competitive index; DSS, decision support system; HPMY, highest percent maximum yield; PMY, percent maximum yield; TCL, total competitive load.

(222) The Residual Effect of Organic Amendment Applications on the Yield of Sweet Corn, Zucchini, and Mustard Cabbage

A major issue in the preparation of nutrient budgets for organic farmers is the residual nutrient effect from organic amendments available for follow-up crops in year-round rotation systems. A series of separate experiments were conducted to evaluate: 1) the residual nutrient effects on double-cropped sweet corn from initial applications of several organic amendments locally available in Oahu, Hawaii; 2) the residual effect of double cropped zucchini; and 3) mustard cabbage from the application of similar organic amendments. The sweet corn experiment consisted of six treatments, with organic amendments applied only prior to the first planting. The second follow-up sweet corn planting was grown without additional amendment applications. Treatments included: 1) a fruit fly based compost; 2) aged chicken manure; 3) bone meal; 4) synthetic fertilizer (farmer's practice); 5) a combination of compost and fertilizer; and 6) a combination of compost and chicken manure. The experiment was arranged with a randomized complete-block design. Each treatment plot consisted of two 20-m long rows of corn with five replications per plot for a total of 30 treatment plots. On a separate location similar trials were conducted on long-term organic farming plots, with double cropped zucchini and with double cropped mustard cabbage. The results from this research shows that crop yields were similar or greater under the organic amendment plots compared to the synthetic fertilizer plots. In crops with a high N uptake demand, yields from the organic amendment plots declined by about 10% in follow-up plantings. This data will allow organic farmers to prepare nutrient budgets to better match their organic fertilizer applications with crop nutrient demands.

Microclimatic and Rooting Characteristics of Narrow‐Row versus Conventional‐Row Corn

Narrow‐row corn (Zea mays L.) has been advocated in recent years for bolstering production, but previous studies have failed to elucidate the complexity of factors that promote the production of corn sown in narrow rows. This study was undertaken to identify those agronomic and microclimatic factors that influence grain yield of corn grown in narrow and wide conventional rows. A split plot experimental design was established near Morris, MN, in 1998 and 1999 with row spacing (0.38, 0.57, and 0.76 m) as the main treatment and corn hybrid (Pioneer 3893 and DeKalb 417) as the secondary treatment. Root length density, crop water use, interception of photosynthetically active radiation (PAR), soil temperature, and soil evaporation were measured in each row‐spacing treatment during the growing season. Grain yield and water use of narrow‐row corn equaled, or even exceeded, that of wide, conventional‐row corn. Narrow‐row corn had a more uniform root distribution and intercepted 5 to 15% more PAR on clear days, the latter of which likely aided in suppressing soil temperatures and evaporation during vegetative growth compared with corn grown in conventional rows. The results of this study suggest that any yield advantage to growing corn in narrow rows may result from establishing a more uniform root and leaf distribution that aids in exploiting soil water and light resources and reducing soil temperatures and evaporation compared with corn grown in wide conventional rows.

Integrated Management of Cogongrass [Imperata cylindrica (L.) Rauesch.] in Corn Using Tillage, Glyphosate, Row Spacing, Cultivar, and Cover Cropping

Cogongrass [Imperata cylindrica (L.) Raeusch.] is a major weed in the tropics where land is intensively cultivated and fallow duration is less than 5 yr. Field studies were conducted in 1999 and 2000 in Nigeria to evaluate cogongrass response to combinations of five weed control options. Treatment combinations were tillage (hoe tillage and no‐tillage), corn (Zea mays L.), row spacing (50 and 75 cm), corn cultivar [open‐pollinated (OP) and hybrid], herbicide (glyphosate and no glyphosate), and cover crop {velvetbean [Mucuna cochinchinensis (Lour) A. Chev] and no velvetbean}. The treatment combinations were arranged in a randomized complete block design with three replications. Integrating tillage, herbicide, and cover cropping with velvetbean gave optimal control of cogongrass. Corn height and leaf area were negatively correlated with cogongrass shoot, rhizome, and total biomass. Corn grain yield was negatively correlated with cogongrass shoot biomass and total cogongrass biomass (shoot + rhizome). Good control of other weeds was achieved through the use of narrow corn row spacing and cover cropping with velvetbean. Tillage, narrow corn row spacing, and the use of herbicide had a positive effect on corn grain yield. The use of competitive cultivars, narrow row spacing, cover crop, and herbicide may be sustainable approaches to the control of cogongrass and other weeds in corn.

Soil fertility distributions in long-term no-till, chisel/disk and moldboard plow/disk systems

In permanent no-till (NT), soil nutrients are no longer mixed into the topsoil as with moldboard plow/disking (MD), whereas chisel/disking (CD) does limited mixing. Surface broadcast and/or banded nutrient applications may result in high and low fertility zones in permanent NT, with possible implications for soil sampling and nutrient placement. We investigated effects of 25 years of continuous NT, CD and MD with corn planted in the same row locations on organic matter (SOM), pH-H 2O and Mehlich-3 extractable phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg). Vertical distribution at 0–5, 5–10 and 10–15 cm depths was measured as well as horizontal distributions across corn rows. We observed higher SOM and P in NT and CD than in MD in the 0–15 cm layer. SOM content was greatest in the top 5 cm in NT, but declined sharply with depth. SOM content in CD was not as high at the surface as in NT, but did not decline as fast as in NT. SOM was uniform but low throughout the 0–15 cm depth of MD. In all tillage systems, SOM did not vary across rows. Soil pH was higher in the 0–5 cm layer of NT than the deeper layers but the reverse was true in the CD or MD treatments. Concentrations of P, K and Ca were higher in the surface 0–5 cm than 10–15 cm depth of all tillage systems, but most strikingly in NT and CD. Starter fertilizer injection resulted in higher P and lower pH in the injection zone of all tillage treatments, but most notably in NT. The pH was depressed under the band of side-dressed nitrogen with all tillage systems. Potassium accumulated in the rows of the previous crop, probably because it leached from crop residue that accumulated there. Tillage did not affect Mg distribution. Optimal nutrient management in NT should take account of horizontal and vertical nutrient and pH distributions. Samples in long-term NT could potentially be taken to a shallower depth if calibration curves are available. To avoid underestimating P and K availability or overestimate lime needs, high P or decreased pH bands should be avoided, as well as crop rows. Possibilities to reduce P and K applications with banding need more investigation. Results show the importance of regular liming in NT to maintain surface pH in the optimum range, but also show that lime does not have to be incorporated.

Root Segregation of C3 and C4 Species Using Carbon Isotope Composition

Partitioning roots for studying cropping systems containing more than one species is important since root growth interaction could influence system performance. The study objective was to test a method for segregating plant species roots from soil samples taken in a mixed stand of corn (Zea mays L.), a C4, and kura clover (Trifolium ambiguum M. Bieb.), a C3 plant. Soil cores containing both corn and kura clover roots were obtained at three distances from the corn row and at two depths in a Rozetta silt loam soil (moderately well drained, fine‐silty, mixed, superactive, mesic Typic Hapludalf). Root composition of these C4 and C3 species was based on 13C/12C ratios expressed as δ13C. A significant linear relationship (r2 = 0.99) was found between the δ13C and the percentage of corn roots in samples containing known ratios of corn and kura clover roots. This relationship was used to determine corn and kura clover root percentages in field samples. Ratios of 13C/12C effectively segregated corn and kura clover root materials obtained from soil samples and seem to be a powerful tool for partitioning roots of C3 and C4 plants in similar studies.

Growth Stage, Development, and Spatial Variability in Corn Evaluated Using Optical Sensor Readings*

ABSTRACT Knowing the exact stage of growth where expressed plant variability is at a maximum might lead to the identification of times when in-season fertilization could have the greatest impact. One field experiment was initiated to measure daily plant growth and spatial variability in corn (Zea mays L.) over the entire growth cycle using optical sensor readings (normalized difference vegetative index, or NDVI) collected every 0.05 m in length, 0.6 m wide from 4 corn rows, 27 m in length. Averaged over all 4 rows, plants were spaced 21 ± 7 cm apart. For each row and sensing date, the mean, standard deviation, and coefficient of variation (CV) were computed from the NDVI readings. Eighteen days after planting, NDVI values were near 0.20, and later peaked near 0.81, 54 days after planting at the 10-leaf growth stage (V10). Coefficients of variation were found to peak much earlier, 33 to 35 days after planting at the 6-leaf growth stage (V6), (31% to 34% during this period). Expressed spatial variability decreased from >30% at V6 to just under 10% at the 11-leaf growth stage (V11). Immediately following V11, a distinct increase in CVs was found just following the initiation of tasseling (VT), but lasted for only 2 days. Expressed spatial variability was greatest at the V6 growth stage, and this peak in the within-row-by-plant variability may be the precise growth stage at which treating that variability will have the greatest impact.

Twin-Row Corn Production: An Evaluation in the Mid-Atlantic Delmarva Region

Corn (Zea maize L.) produced in twin rows (two rows 7.5 inches apart on 30-inch centers) was compared to corn produced in rows spaced 30 inches apart over a range of plant populations at three Maryland locations and one Delaware location during 2003 and 2004. Grain yield averaged over the hybrids and populations differed between the two row spacing treatments at only one of the four locations and in that instance yield was greater in 30-inch rows. Corn produced in twin rows did not produce significantly better yields as plant population increased from 24,000 to 32,000 plants per acre. Only one of twenty-eight hybrid by row spacing combinations evaluated across the four locations had a significant linear response to population for yield. Yield response to population for both row spacing treatments varied across locations and hybrids. Greater levels of lodging occurred as population increased for twin-row corn. A greater incidence of stalk rot was also observed in twin-row corn. These results did nothing to indicate that planting corn in twin rows instead of the conventional 30-inch rows in the Delmarva region would be a beneficial management practice change.

Zone herbicide application controls annual weeds and reduces residual herbicide use in corn

Abstract To minimize the chance of surface water contamination by herbicides, farmers need alternative ways to manage weeds in field crops, such as field corn, that reduce herbicide use. Zone herbicide application (ZHA) reduces herbicide use compared with conventional broadcast herbicide application by (1) banding low herbicide rates between corn rows (≤ 1× normal broadcast registered rate), (2) managing crops to favor crop competition, and (3) banding very low herbicide rates over crop rows (≪ 1× normal rate). The research goal was to compare the relative effectiveness of reduced-rate ZHA with broadcast herbicide application on in-row (IR) and between-row (BR) summer annual weed cover (chiefly giant foxtail and waterhemp species), grain yields, and net returns resulting from herbicide application in field corn. Preemergence ZHA of atrazine + metolachlor + clopyralid + flumesulam was made in zones (i.e., even width bands) at different rates between and over crop rows for three site-years in Missouri, and ...

Red–far-red ratio of reflected light: a hypothesis of why early-season weed control is important in corn

A plant's ability to detect and adjust morphologically to changes in light quality (red–far-red [R:FR] ratio) is one mechanism by which a crop plant responds to weeds. To test this hypothesis, two experiments were conducted where corn was grown in growth cabinets under different light environments. First, to determine the effect of R:FR ratio on corn growth and development, treatments of high R:FR (1.37) and low R:FR (0.67) ratio were compared. These were established by planting corn in pots and then placing trays of either turface (a baked clay medium with high R:FR) or commercial grass sod (low R:FR) on each side of a row of corn pots. Grass sod was used to simulate low-growing weeds. The low R:FR sod treatment resulted in corn plants which were taller, had larger leaves, and greater shoot–root ratio than plants growing in the high R:FR turface treatment. In the second experiment, the effect of R:FR ratio on corn leaf azimuth position was examined. This was accomplished by adding a third treatment where each corn row had sod placed on one side and turface on the other. The proportion of leaves in four azimuthal classes was recorded. In the presence of sod, the proportion of leaves perpendicular to the corn row decreased, and this altered the proportion of leaves in other classes. Therefore, corn seedlings detected changes in light quality caused by the presence of sod (which simulated low-growing weeds) and responded by adjusting carbon allocation and leaf orientation to optimize the interception of light quantity and quality. These results support our hypothesis that low-lying vegetation can alter the growth of corn seedlings before competition for resources occurs. This change in growth may help explain the importance of early-season weed control in corn.

Microenvironment of a corn–soybean–oat strip intercrop system

The microenvironment of a corn ( Zea mays L.)–soybean ( Glycine max [L.] Merr.)–oat ( Avena sativa L.) narrow strip intercrop system was studied on four farms in Iowa, USA during 1991–1993 (one or two farms studied each year) with the objective of explaining previously observed patterns of strip-crop yields. Air and soil temperatures, humidity, wind, and photosynthetic photon flux density (PPFD) for each row in a strip were recorded continuously during 4–13-day periods several times during each growing season; short-term measurements of light extinction through the corn and soybean canopies were made late in the 1993 growing season. Soybean biomass in September 1993 was also determined. Early in the growing season, there typically were no significant differences among rows within a strip in any environmental or growth variable. Later in the growing season, daily PPFD received varied more across each strip than any other environmental variable measured; the outer side of edge rows of corn in north–south rows typically received significantly higher daily PPFD (2–38% more) than inner rows in the strip, while the outside of the soybean row furthest from corn received 36–140% greater PPFD than the corn-side of the row next to the corn strip. Soybean height; leaf mass per leaf area; and leaf mass, stem mass, and pod mass per unit land area in September were strongly related to daily PPFD, with all except height increasing with greater PPFD. Total biomass increased by 32% from the row closest to corn to the row furthest from corn, although there was no change in the ratio of leaf:stem:pod with row position. Thus, PPFD varied the most across the strips of any environmental variable, and crop growth was closely related to PPFD received.

Response of Corn Grain Yield to Spatial and Temporal Variability in Emergence

Potential yield benefits from improving within‐row plant spacing variability and plant emergence variability in corn (Zea mays L.) production are often questioned by growers. Research was conducted at two locations in south‐central Ontario during a 2‐yr period to quantify the effects and interactions of plant spacing variability and plant emergence variability on growth and grain yield of corn. Nine treatments were established by hand planting corn rows with repeating six‐plant sequences consisting of uniform and nonuniform spacing, even and uneven emergence, and their combinations. Spacing treatments consisted of (i) uniform within‐row plant spacing of 20 cm; (ii) one 40‐cm gap associated with a double; and (iii) one 60‐cm gap associated with a triple in each six‐plant sequence. Emergence treatments included uniform early emergence, a two‐leaf stage delay, and a four‐leaf stage delay for one plant in each six‐plant sequence. Only plant emergence variability significantly affected plant height, leaf area index (LAI), dry matter accumulation, and grain yield. Compared with the uniformly early emerged plants, one out of six plants with a two‐leaf stage delay in emergence reduced yield by 4%, and one out of six plants with a four‐leaf stage delay reduced yield by 8%. Whereas corn plants next to a gap demonstrated compensatory growth, plants adjacent to a late emerging corn plant did not exhibit compensatory growth. These results indicate that corn is more responsive to plant emergence variability than plant spacing variability. Variation in plant emergence reduced yield, whereas variation in within‐row spacing did not affect yield, and interactions between the two factors were not significant.