Rate Of Corn Research Articles

Simulated dormant peppermint (Mentha × piperita) response to mesotrione: a greenhouse study

AbstractA dose-response trial was conducted in two experimental runs at the Purdue University Horticulture Greenhouses, West Lafayette, IN, in 2021/2022 to determine the effect of mesotrione rate on simulated dormant ‘Redefined Murray Mitcham’ peppermint. Peppermint was established in 20-cm-diam polyethylene pots, it was then harvested, and pots were placed in a cooler (4 C) for 1 mo. Potted peppermint plants were removed from cold storage and treated with one of five mesotrione rates: 0 (nontreated control), 53, 105, 210, or 420 g ai ha–1. As mesotrione rate increased from 53 to 420 g ai ha–1, predicted peppermint injury increased from 35% to 80% at 2 wk after treatment (WAT), 36% to 95% at 4 WAT, 9% to 82% at 6 WAT, and 8% to 90% at 8 WAT; and peppermint height decreased from 74% to 42% of the nontreated control (7 cm) 2 WAT, 74% to 17% of the nontreated control (20 cm) 4 WAT, 81% to 15% of the nontreated control (28 cm) 6 WAT, and 88% to 19% of the nontreated control (37 cm) 8 WAT. Mesotrione rates from 53 to 420 g ai ha–1 reduced peppermint dry weight from 40% to 99%, respectively. Results from this experiment showed that mesotrione applied even at half of the recommended field use rate for corn (53 g ai ha–1) was not safe for peppermint due to a reduction in aboveground biomass.

Rhizobacteria of Bali With Obvious Growth-Promoting Properties on Corn (Zea mays L.)

Corn productivity in Indonesia is still relatively low compared with other countries. Therefore, it is necessary to increase the productivity of corn by using rhizobacteria, which have multiple traits. This study was conducted to obtain indigenous rhizobacteria of Bali that have multiple traits, can produce indoleacetic acid (IAA), fix nitrogen from atmosphere, produce siderophores, colonize roots, increase seed germination, and promote the growth of corn. Isolation of rhizobacteria was carried out from the rhizosphere of plants belonging to the Gramineae family that grows in Bali Island, Indonesia. Six isolates, namely, Sr3, Tb9, Rg1, Rg23, Al27, and Jg8, could produce IAA, fix nitrogen from the atmosphere, produce siderophores, and increased germination rate and vigor index of corn seedling. Among them, three isolates, namely, Rg1, Sr3, and Jg8, significantly (p <0.05) increased the germination rate of corn seeds, increased vigor index, increased root dry weight and shoot dry weight of corn at the age of 7 days, and were able to colonize corn roots. Compared with the control, the rhizobacteria treatment increased the germination of corn seeds ranging from 5.04 to 13.05%. Based on the analysis of the 16S rRNA gene, it was found that these rhizobacteria species were Glutamicibacter nicotianae strain Rg1 (accession number OM349119), Brevibacillus invocatus strain Sr3 (accession number OM327515), and Micrococcus luteus strain Jg8 (accession number OM362349). Under a greenhouse condition, all the three isolates significantly (p <0.05) increased nutrient uptake, the leaf chlorophyll content, net assimilation rate, and crop growth rate of corn when compared with control. These results suggested that these isolates of rhizobacteria obviously promoted the growth of corn and can be developed as biostimulant to promote the growth and increase the corn yield in Bali, Indonesia.

Long-term no-till increases soil nitrogen mineralization but does not affect optimal corn nitrogen fertilization practices relative to inversion tillage

No-till management is a proven practice for increasing soil organic matter in many environments. By increasing soil organic matter, no-till may increase soil N mineralization, potentially reducing crop demand for N fertilizer relative to inversion tillage. In this study, we hypothesized that, relative to inversion tillage (moldboard plowing), long-term no-till would: i) increase total N stocks, ii) increase mineralized N during the growing season, iii) increase grain yield and N uptake, and iv) reduce reliance of corn (Zea mays L.) on N fertilizer inputs. We tested these hypotheses in a long-term, continuous corn tillage and fertilizer N rate study located in Lexington, KY. We measured the total soil N and potentially mineralizable N after 48 years, the in situ mineralized N and N uptake during two corn seasons (2018–2019), and the corn grain yield for five seasons (2015–2019). We evaluated the effect of no-till on N fertilizer reliance in two ways – the first was by measuring the agronomic optimum N rate of corn in the two tillage systems, and the second was by measuring the corn yield response to late N fertilization timing in the two tillage systems. We found that the no-till system had 1000 kg N ha−1 greater total soil N stocks in the top 20 cm, mineralized 65 kg ha−1 more N during corn growth, and resulted in 22−71 kg N ha−1 and 780−1800 kg ha−1 greater N uptake and grain yield across N rates, respectively, than the plowed system. The agronomic optimum N rate (AONR) did not differ among tillage treatments, potentially because the no-till treatment yielded more and thus demanded more N. Although corn yield responded to the late N fertilization treatment, the response was similar in both the no-till and plowed treatments. We conclude that long-term no-till increases soil N mineralization and corn yield relative to inversion tillage, with minimal effect on the AONR or optimal timing of N fertilizer application.

Corn and soybean response to sulfur fertilizer in West Tennessee

AbstractWith improved crop yields and reduced atmospheric S deposition, Mid‐South U.S. soils may require S fertilization in deficient soils. The objectives of this study were to identify optimal at‐planting S rate for corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yield, and evaluate the impact of S rate on crop growth, leaf nutrient level, and seed S. Small plot replicated field studies were conducted in 2015 and 2016 at a S‐deficient site in Milan, TN. Ammonium sulfate [(NH4)2SO4] was broadcast applied at planting at 0, 10, 20, and 30 lb S acre–1. Soybean leaf S concentration at early bloom was similar to the zero S control, but concentrations of Fe, Mn, and Cu were reduced, and Zn was increased. These effects increased with S rate. Corn leaf tissue S concentration increased with S rate at sixth‐leaf and silking, while Fe, Mn, and Cu decreased as S rate increased, similar to the soybean experiment. Soybean seed S level increased with rate of S, while corn seed S increased with lowest S rate but did not respond to S rate. Seed N and seed weight were not affected by S rate for either crop. The small increase in soybean yield was not significant. Corn yield increased with applied S in both years. Overall, application of S fertilizer at ≥10 lb S acre–1 improved corn but not soybean yield in a low soil organic matter (SOM), S deficient medium‐textured soil.

A computer vision approach to improving cattle digestive health by the monitoring of faecal samples

The digestive health of cows is one of the primary factors that determine their well-being and productivity. Under- and over-feeding are both commonplace in the beef and dairy industry; leading to welfare issues, negative environmental impacts, and economic losses. Unfortunately, digestive health is difficult for farmers to routinely monitor in large farms due to many factors including the need to transport faecal samples to a laboratory for compositional analysis. This paper describes a novel means for monitoring digestive health via a low-cost and easy to use imaging device based on computer vision. The method involves the rapid capture of multiple visible and near-infrared images of faecal samples. A novel three-dimensional analysis algorithm is then applied to objectively score the condition of the sample based on its geometrical features. While there is no universal ground truth for comparison of results, the order of scores matched a qualitative human prediction very closely. The algorithm is also able to detect the presence of undigested fibres and corn kernels using a deep learning approach. Detection rates for corn and fibre in image regions were of the order 90%. These results indicate the potential to develop this system for on-farm, real time monitoring of the digestive health of individual animals, allowing early intervention to effectively adjust feeding strategy.

MODELING EVAPOTRANSPIRATION FOR C4 and C3 CROPS IN THE WESTERN LAKE ERIE BASIN USING REMOTE SENSING DATA

Abstract. Growing monoculture impacts not just soil properties and biodiversity but also local hydrology including evapotranspiration (ET). The Midwest region of the U.S. is known for its monoculture trend by growing and producing corn, which commonly replaces other crop types. In addition to large areas covered with corn, the photosynthetic adaptations of corn, being the C4 crop, affects ET differently than other C3 crops such as soybean, wheat, and alfalfa. This study aims to model and compare ET for C3 and C4 crops using remote sensing (Sentinel-2 data) and the Boreal Ecosystem Productivity Simulator (BEPS) model, modified to consider C3 and C4 crops. The study explores the ET rate trend for corn and soybean in an agriculture area situated in the Western Lake Erie Basin, where the balance between evapotranspiration, groundwater level, and surface runoff may play a role in agricultural runoff and Lake Erie’s algal blooms caused by runoff pollution. The results suggest that the monthly average ET rates for both soybean (C3) and corn (C4) reach its maximum at the mid-to-late growing season. However, the ET rate for corn is higher than for soybean in the early season (June) (ET = 121 mm month−1 for corn; ET = 105 mm month−1 for soybean), while the ET rate for soybean becomes higher than for corn soon after (July) and becomes considerably higher in August (ET = 181 mm month−1 for corn; ET = 218 mm month−1 for soybean). It is surmised that the higher ET rate for corn in the early growing season is due to nitrogen-based fertilizer commonly applied to corn parcels at that time, whereas soybean growth is based on biological nitrogen fixation.

Long‐term evapotranspiration rates for rainfed corn versus perennial bioenergy crops in a mesic landscape

AbstractPerennial cellulosic crops are promoted for their potential contributions to a sustainable energy future. However, a large‐scale perennial bioenergy production requires extensive land use changes through diversion of croplands or conversion of uncultivated lands, with potential implications for local and regional hydrology. To assess the impact of such land use conversions on ecosystem water use, we converted three 22 year‐old Conservation Reserve Program (CRP) grasslands and three 50+ year‐old conventionally tilled corn‐soybean crop fields (AGR) to either no‐till continuous maize (corn) or perennial (switchgrass or restored prairie) bioenergy crops. We also maintained one CRP grassland without conversion. We measured evapotranspiration (ET) rates on all fields for 9 years using eddy covariance methods. Results show that: (a) mean growing‐season ET rates for perennial crops were similar to the ET rate of the corn they replaced at the previously cultivated (AGR) field but ET rates for perennial crops at CRP fields were 5–9% higher than ET rate for corn on former CRP fields; and (b) mean nongrowing season ET rates for perennial fields were 11–15% lower than those for corn fields, regardless of land use history. On an annual basis, mean ET rates for perennial crops tended to be lower (4–7%) than ET rate of the corn that they replaced at AGR fields but ET rates for perennial crops and corn at CRP fields were similar. Over 9 years, mean ET rates for the same crop across land use histories were remarkably similar for corn, whereas for the perennial crops they were 4–10% higher at former CRP than at former AGR fields, mainly due to differences in growing season ET. Over the 9 years and across all fields, ET returned ~60% of the precipitation back to the atmosphere. These findings suggest that large‐scale substitution of perennial bioenergy crops for rainfed corn in mesic landscapes would have little if any (0 to −3%) impact on terrestrial water balances.

Transgenic Corn Response to Nitrogen Rates under Corn Rootworm Pressure

Core Ideas Bacillus thuringiensis rootworm traits and corn rootworm feeding affected N uptake and root mass. N uptake by DK44‐61 SSX at V6 lagged DK46‐60 VT3 and DK 44‐92 RR2. DK44‐92 RR2 had a larger root system at V6 than either DK46‐60 VT3 or DK44‐61 SSX. Rootworm injury limited N uptake, root mass of DK44‐92 at V12 compared to Bt hybrids. Root mass, trait efficacy, and root injury interplay with N rate have insect resistance management implications. Recommended N rates for corn (Zea mays L.) typically consider yield, economic, and environmental dimensions, but not optimal protection by Bacillus thuringiensis (Bt) Berliner‐based traits against corn rootworm (CRW) (Diabrotica spp.). This research explored N rate effects on CRW trait performance under CRW pressure. The experiment featured a split‐plot randomized complete block design with factorial treatment combinations of N rates and hybrids differing in CRW traits. Root mass, N uptake, CRW efficacy, and grain yield data were collected from two locations in 2011. Root mass at growth stage V6 (before CRW injury) increased with N rate and was greater in the Roundup Ready (RR2) hybrid (Monsanto, St. Louis, MO) by 30.6%. Nitrogen uptake was similar between VT Triple (VT3) (Monsanto, St. Louis, MO) and the RR2 hybrids, which exceeded the SmartStax (SSX) (Monsanto, St. Louis, MO: Dow AgroSciences Indianapolis, IN) hybrid by 12.5%. By growth stage V12, CRW injury in the RR2 vs. Bt hybrids reduced N uptake by 42.0%, Beetle emergence was reduced 66 to 91% by Bt hybrids. Yield response to N differed between hybrids at only one site: the CRW‐injured RR2 hybrid was unable to utilize increasing N rates while the SSX hybrid did not plateau. Recommended N rates (134–185 kg N per ha−1) were sufficient to optimize root mass, N uptake, root protection, and yield under a low stress, modest CRW‐pressure environment: however, low N resulted in poor performance of these hybrids, suggesting further exploration of N rate effects when N loss or denitrification is present.

Does Total Nitrogen/Sulfur Ratio Predict Nitrogen or Sulfur Requirement for Corn?

Core Ideas Nitrogen and sulfur can interact within the plant and affect the concentration of each other in corn plant tissue. Nitrogen concentration in plant tissue has a greater impact on the N/S ratio than S which was found to not affect the N/S ratio in corn ear leaf tissue and grain. Individual sufficiency of N and S in plant tissue is a better predictor of corn yield response versus the ratio of N/S in the plant tissue. The accumulation of nitrate–N in the base of the corn stalk assessed at maturity is decreased when sulfur fertilizer is applied. Excess sulfate can accumulate in the base of the plant at maturity but the amount of sulfate–S cannot be used to predict the sufficiency of S. Nitrogen and S can interact within the corn (Zea mays L.) plant. The objectives of this study were to evaluate in corn (i) the effect of N and S on nutrient uptake and grain yield, (ii) use of tissue total N/S ratio to predict grain yield, and (iii) the impact of applied SO4–S on basal stalk NO3–N concentration. Treatments were applied as a factorial design. Factor 1 consisted of 0 or 28 kg S ha‐1. Factor 2 consisted of 0, 56, 112, 168, 224, and 280 kg N ha‐1. Fertilizer N increased the concentration of N and S in corn R1 leaf tissue, N concentration in grain, relative grain yield, grain removal of N and S, and NO3–N in the basal stalk. Fertilizer S increased R1 leaf N and S concentration, decreased basal stalk NO3–N, and increased corn grain yield when N was applied at a rate that maximized corn grain yield. The total N/S ratio in corn R1 leaf and harvested grain were affected by N application but not by S addition. Basal stalk N/S ratio was affected by both N and S. A critical N/S ratio could not be identified to predict corn grain yield response. While the data support a general effect of N and S on the uptake of each other, fertilization with N or S should be based on potential for increased grain yield from either nutrient. Based on results, optimal N rates for corn are not affected if S is also applied.

Atividade Agrícola: Uma Análise sobre a sua Contribuição para a Economia do Estado de Minas Gerais e seus Possíveis Determinantes Agrícolas

A partir da aplicação da análise de regressão linear múltipla, pelo método stepwise, em um conjunto de dados tabulados pelo IBGE referentes a 849 municípios do estado de Minas Gerais, e, ainda, dos respectivos valores totais da produção agrícola de cada uma das 33 culturas permanentes e 31 culturas temporárias produzidas em cada um daqueles municípios, o presente estudo teve por objetivo, inicialmente, avaliar a influência do valor adicionado bruto da agropecuária sobre o Produto Interno Bruto (PIB) dos municípios mineiros, e, especificamente em relação à agricultura, identificar como os valores totais da produção agrícola dos municípios do estado de Minas Gerais poderiam constituir-se em direcionadores do valor adicionado bruto da agropecuária daqueles municípios. Entre outros resultados, observou-se indícios de que o valor adicionado bruto da agropecuária contribui para a formação do PIB dos municípios mineiros, contudo, pelo menos estatisticamente, a influência dos segmentos do setor de serviços e da indústria parece ser bem mais expressiva. Também se percebeu que o valor da produção das culturas do milho em grão, cana de açúcar, café em grão e manga, em conjunto, explicam 93,7% das observações referentes aos 849 municípios mineiros integrantes da amostra dessa pesquisa, sendo que, os valores da produção das outras 13 culturas agrícolas identificadas como possíveis determinantes do valor adicionado bruto da agropecuária municipal mineira foram capazes de explicar, em conjunto, apenas 9,4% daquelas observações.

Influence of Nitrogen Application Rate and Timing on Grain Yield, Phyllochron and Leaf Appearance Rate of Corn (Zea mays L.)

Influence of Nitrogen Application Rate and Timing on Grain Yield, Phyllochron and Leaf Appearance Rate of Corn (Zea mays L.)

Crop Utilization of Nitrogen in Swine Lagoon Sludge

Swine lagoon sludge is commonly applied to soil as a source of nitrogen (N) for crop production but the fate of applied N not recovered from the soil by the receiver crop has received little attention. The objectives of this study were to (1) assess the yield and N accumulation responses of corn (Zea mays L.) and wheat (Triticum aestivum) to different levels of N applied as swine lagoon sludge, (2) quantify recovery of residual N accumulation by the second and third crops after sludge application, and (3) evaluate the effect of different sludge N rates on nitrate (NO3-N) concentrations in the soil. Sludge N trials were conducted with wheat on two swine farms and with corn on one swine farm in the coastal plain of North Carolina. Agronomic optimum N rates for wheat grown at two locations was 360 kg total sludge N ha−1 and the optimum N rate for corn at one location was 327 kg total sludge N ha−1. Residual N recovered by subsequent wheat and corn crops following the corn crop that received lagoon sludge was 3 and 12 kg N ha−1, respectively, on a whole-plant basis and 2 and 10 kg N ha−1, respectively, on a grain basis at the agronomic optimum N rate for corn (327 kg sludge N ha−1). From the 327 kg ha−1 of sludge N applied to corn, 249 kg N ha−1 were not recovered after harvest of three crops for grain. Accumulation in recalcitrant soil organic N pools, ammonia (NH3) volatilization during sludge application, return of N in stover/straw to the soil, and leaching of NO3 from the root zone probably account for much of the nonutilized N. At the agronomic sludge N rate for corn (327 kg N ha−1), downward movement of NO3-N through the soil was similar to that for the 168 kg N ha−1 urea ammonium nitrate (UAN) treatment. Thus, potential N pollution of groundwater by land application of lagoon sludge would not exceed that caused by UAN application.

Preliminary Study on the Chemical Components of the Slag and Its Feasibility for Soil Improvement

In this study,we measured and analyzed the chemical composition of the slag. Different seeds( corn, eggplant,rice and periwinkle) were planted in the heavy( mild) saline-alkali soil and slag with HPMA agent. The growth of plants was observed,the feasibility of using this waste for soil improvements is the aim of this study. Comparison between slag and different soils showed that both had the similar chemical composition. Some components including CaO,Fe 2 O 3,MgO,MnO 2 in slag was obviously higher than the soil,while some others including TiO 2,K 2 O,Na 2 O,P 2 O 5 in slag was not detectable. Together with HPMA agent,slag mixing with saline alkali soil( heavy and mild) could significantly improve germination and growth rate of corn,eggplant, rice and periwinkle. Compared with typical greenhouse soil conditioners of vermiculite and perlite,similar germination and growth rate in different plants were observed in the slag matrix. Furthermore,similar to the function of flower soil( peat),germination and growth rate of variable plants manifested that mixture of slag and bark soil( an abundant local resource) can be used as a compound soil conditioner,which can enrich soil fertility and improve soil physical structure. The preliminary study showed that the slag can be used for saline- alkali soil improvement and the soil structure improvement for facilities agriculture. It also has the potential for the formation of compound soil conditioner combined with the local bark soil resources.

Effects of Different Micro-Catchment Mulching Methods on Growth and Water Use Efficiency of Corn

The study on the effects of three unary and binary micro-catchment mulching methods including film mulching ridge and ditch plantation, film-mulching ridge and ditch film-mulching plantation and film-mulching ridge and ditch film-mulching straw plantation on growth of corn and different precipitation years was conducted in allusion to the low and unstable yield of corn in the western Liaoning province of China and in comparison with the traditional plantation model. Under the condition of this experiment, through film-mulching ridge and ditch film-mulching plantation and film-mulching ridge and ditch plantation, the time for seedling emergence of corn was shortened and the emergence rate of corn was increased. Through film-mulching ridge and ditch film-mulching straw plantation, the time for seedling emergence of corn was prolonged and the emergence rate of corn was increased in median water or dry years, but the emergence rate of corn was reduced in the high flow year. By contrast to traditional plantation model, film-mulching ridge and ditch film-mulching plantation and film-mulching ridge and ditch plantation boosted the increase in plant height and leaf area of corn and promoted dry matter accumulation in the early period of growth while the growth was slow, the plant height, leaf area and dry matter accumulation was always at he minimum value through film-mulching ridge and ditch straw mulching plantation in the early period of growth, but the growth rate was expedited in the late period during growth. Through film-mulching ridge and ditch straw mulching plantation, due to many reasons such as the growth process ahead of schedule and high temperature, the signs of precocity or premature senility come into being and leaf area and chlorophyll content decreases swiftly; through film-mulching ridge and ditch straw mulching plantation, the descent velocity of leaf area and chlorophyll content were reduced and the leaf senescence was postponed. In different precipitation years, the increases in water use efficiency of micro-catchment plantation were different, smaller in high flow year while larger in dry or median water year.

Development of Feeding Rate Detection Sensor Based on Wireless Technology

Feeding rate measurement is one of the most critical technologies in precision agricultural system. In present study, a wireless sensor was constructed to detect the feeding rate for corn combine harvester. Torsional strain gauges were fixed in the modified sprocket at header auger to measure the flow rate of collected corn in a form of torque. The force change was then transformed into voltage signal, which could be transmitted by Zigbee wireless module integrated in the sensor. To evaluate the reliability of the sensor, field study was conducted to develop a model between feeding rate and wheel torque. Obtained results showed that the developed sensor could detect the change of feeding rate, and further work should be conducted to calibrate the accuracy of the sensor.

Sensor‐Based Nitrogen Applications Out‐Performed Producer‐Chosen Rates for Corn in On‐Farm Demonstrations

Optimal N fertilizer rate for corn (Zea mays L.) and other crops can vary substantially within and among fields. Current N management practices do not address this variability. Crop reflectance sensors offer the potential to diagnose crop N need and control N application rates at a fine spatial scale. Our objective was to evaluate the performance of sensor‐based variable‐rate N applications to corn, relative to constant N rates chosen by the producer. Fifty‐five replicated on‐farm demonstrations were conducted from 2004 to 2008. Sensors were installed on the producer's N application equipment and used to direct variable‐rate sidedress N applications to corn at growth stages ranging from V6 to V16. A fixed N rate chosen by the cooperating producer was also applied. Relative to the producer's N rate, sensors increased partial profit by $42 ha−1 (P = 0.0007) and yield by 110 kg ha−1 (P = 0.18) while reducing N use by 16 kg N ha−1 (P = 0.015). This represents a reduction of approximately 25% in the amount of N applied beyond what was removed in the grain, thus reducing unused N that can move to water or air. Our results confirm that sensors can choose N rates for corn that perform better than rates chosen by producers.

Effects of Winter Manure Application in Ohio on the Quality of Surface Runoff

Winter application of manure poses environmental risks. Seven continuous corn, instrumented watersheds (approximately 1 ha each) at the USDA-ARS North Appalachian Experimental Watershed research station near Coshocton, Ohio were used to evaluate the environmental impacts of winter manure application when using some of the Ohio Natural Resources Conservation Service recommendations. For 3 yr on frozen, sometimes snow-covered, ground in January or February, two watersheds received turkey litter, two received liquid swine manure, and three were control plots that received N fertilizer at planting (not manure). Manure was applied at an N rate for corn; the target level was 180 kg N ha(-1) with a 30-m setback from the application area to the bottom of each watershed. Four grassed plots (61 x 12 m) were used for beef slurry application (9.1 Mg ha(-1) wet weight); two plots had 61 x 12 m grassed filter areas below them, and two plots had 30 x 12 m filter areas. There were two control plots. Nutrient concentrations were sometimes high, especially in runoff soon after application. However, most events with high concentrations occurred with low flow volumes; therefore, transport was minimal. Applying manure at the N rate for crop needs resulted in excess application of P. Elevated P losses contributed to a greater potential of detrimental environmental impacts with P than with N. Filter strips reduced nutrient concentrations and transport, but the data were too limited to compare the effectiveness of the 30- and 61-m filter strips. Winter application of manure is not ideal, but by following prescribed guidelines, detrimental environmental impacts can be reduced.

Variability of the Illinois Soil Nitrogen Test across Time and Sampling Depth

There is potential for using the Illinois soil nitrogen test (ISNT) to improve N fertilizer recommendations for crops in the southeastern United States. The ISNT has been previously calibrated to predict N rates for corn (Zea mays L.) in North Carolina. This study evaluated the effects of sampling time, sampling depth, crop rotation, and fertilizer application on soil ISNT‐N during a 2‐yr period in the humid Coastal Plain and Piedmont regions of North Carolina. Ten sites were repeatedly sampled at 0‐ to 10‐, 10‐ to 20‐, and 20‐ to 30‐cm depths in fall, mid‐winter, and spring between October 2006 and May 2007. Illinois soil nitrogen test N, KCl‐extractable soil NO3–N and NH4–N, and soil organic matter (SOM) derived by loss‐on‐ignition (LOI) were evaluated at each sampling. Temporal changes in these soil parameters were evaluated for various crop rotations and N fertilizer applications. Soil ISNT‐N decreased with depth and showed significant variation with time at all three depths at all sites. Soil ISNT‐N was influenced by crop rotation and tillage but was not significantly affected by N fertilizer applications. Considering all sites together, ISNT‐N was well correlated with LOI; however, ISNT‐N was not correlated with LOI across time within sites. This suggests that the ISNT measured a fraction of SOM that behaved somewhat independently with time.

Soybean Residue Management and Tillage Effects on Corn Yields and Response to Applied Nitrogen

Variability in N fertilizer requirements for corn (Zea mays L.) following soybean [Glycine max (L.) Merr.] across sites and years emphasizes the need to understand management practice effects on apparent soybean N contributions. This study was conducted to determine the effects of three soybean harvest management systems (HMS) and tillage on subsequent corn grain yields, and apparent soybean N contributions. Field experiments to evaluate the effects of returning or removing soybean residue, soybean forage harvest at the R6 growth stage, and applied N (0–180 kg N ha−1) on corn grain yields were conducted for 3 yr at four locations. The soybean residue returned treatment significantly decreased yields by 1.1 and 2.5 Mg ha−1 for 2 of 12 site years. The soybean residue returned treatment also required 134, 41, and 87 kg ha−1 more fertilizer N to maximize yields for 3 of 12 site years, but not at the remaining sites. Greater early season soil NO3–N in the forage harvested or residue removed treatments before planting and when corn plants were 30 cm tall (presidedress) is probably a result of warmer soil temperatures and increased soil N mineralization where residue was removed. Economic optimum N rates for corn following soybean varied substantially across sites and years and ranged from 0 to 180 kg N ha−1 but were not greatly affected by soybean HMS or tillage at most sites. This work emphasizes the need for a field‐specific approach to better predict the apparent soybean N contribution to a subsequent corn crop.

Fresh and Composted Paper Sludges Sustain Soil Productivity

In this 5-yr study, application frequency of fresh (FDS) and composted (CDS) paper sludges was evaluated on soil properties and silage corn (Zea maysL.) and barley (Hordeum vulgareL.) yields and N uptake by comparing one application (2000) with repeated applications (2000, 2001, 2002). Treatments consisted of a control with neither amendment nor N fertilizer, a recommended N rate for corn (160 kg N ha−1) and barley (90 kg N ha−1), and FDS and CDS at a rate of 40 Mg ha−1on wet basis with or without reduced N fertilizer (120 kg N ha−1) on corn. Compared to the control, the FDS or CDS applications significantly increased the proportions of soil larger macroaggregates (>2 mm) and the mean-weight diameter (MWD) of aggregates, regardless their application frequency. Single or three yrs additions of FDS or CDS produced, on average, an increase of 25 to 31% of the soil C and N contents compared to the control and the recommended N fertilizer treatment (160 kg N ha−1). In the first year of their application, the FDS or CDS with or without supplemental N fertilizer (120 kg N ha−1) reduced silage corn and N uptake, compared to the control probably due to N immobilization. However, silage corn yields were increased in the following years with one application or with repeated application of FDS or CDS. Results show that benefits on soil properties and crop yields of single application of FDS and CDS were similar to those of the triple applications and were still noticeable a few years following the last application.