Deficiency In Corn Research Articles

Role of sulfur mineralization and fertilizer source in corn and soybean production systems

AbstractSulfur (S) is an important nutrient for plant growth and crop yield. In the northern U.S. Corn Belt, a decrease in atmospheric S deposition and an increase in grain harvest have increased the frequency of S deficiency in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Nevertheless, S deficiency remains difficult to predict owing to complex interactions between the production of plant‐available sulfate‐S from soil organic matter (SOM) mineralization and sulfate‐S losses to leaching. Our objective was to measure corn and soybean yield response to four S fertilizers (ammonium sulfate, elemental S, gypsum, and polyhalite) in the 1st year following fertilizer application and in the 2nd (residual) year following fertilizer application in Iowa. Across 4 site‐years, none of the S fertilizer products increased soybean yield. Across 12 site‐years in the 1st year following application, sulfate‐S based fertilizers increased corn yield in 4 site‐years while elemental S had no effect. Across 6 site‐years in the second residual year following application, elemental S, polyhalite, and gypsum increased corn yield in 1 site‐year while ammonium sulfate had no effect. Laboratory incubations confirmed that there was slower production of plant‐available S from elemental compared with sulfate‐based fertilizers, potentially explaining the lack of elemental S effect in the 1st year following application. In contrast to our expectations, there was a weak, but positive relationship between corn yield response to S fertilizer and SOM concentration. Overall, the kinetics of S fertilizer mineralization and solubility appear to affect the magnitude and timing of crop response to S fertilizer.

Intra-Canopy Sensing Using Multi-Rotor sUAS: A New Approach for Crop Stress Detection and Diagnosis

HighlightsA novel platform was developed for intra-canopy insertion of sensors from a multi-rotor sUAS.The system enables real-time data acquisition from inside the crop canopy comparable to an in-person view.The system provides ideal data for use in modern CNN-based stress diagnosis in row crop production.Abstract. Remote sensing is a critical tool in precision agriculture, giving producers the ability to monitor field conditions throughout the growing season. Although several remote sensing platforms are in use today, small unmanned aerial systems (sUAS) provide the greatest flexibility with the highest resolution. As sUAS capabilities continue to increase (i.e., payload, flight time, and speed), their potential in commercial row crop production is substantial. However, like other forms of remote sensing, traditional sUAS are limited to a nadir view of the target and only capture the top of the crop canopy. Although disease epidemiology and stress origins vary, this limited view usually does not capture the impact of stress at the initial manifestation. For example, stresses such as macronutrient deficiencies in corn originate at the base of the plant and then move upward as nutrients translocate. By the time the stress is detectable at the top of the canopy, the opportunity to mitigate yield loss is limited. A new sUAS platform is needed for sensing beneath the upper portion of the canopy. The Stinger platform, developed to meet this need, consists of a 4.0 m fiberglass rod, custom sensor mount, communication network, and radio link. Using this platform, a variety of sensors can be inserted into the crop canopy from a hovering sUAS. The Stinger platform, when combined with artificial intelligence (AI), significantly expands the capabilities of sUAS for diagnosis of crop stress in row crop production. Keywords: Intra-canopy sensing, Remote sensing, RGB imagery, Stress diagnosis, sUAS.

Is starter phosphorus fertilizer necessary for corn grown on Atlantic Coastal Plain soils?

AbstractProducers managing Coastal Plain soils in Maryland have reported visual symptoms of P deficiency in corn (Zea mays L.) grown on soils with P concentrations above the agronomic optimum range (e.g., 40–84 mg kg–1 Mehlich 3‐extractable phosphorus [M3P]). Yet, corn yield response to starter P fertilizer on soils with M3P concentrations above this range has not been consistently demonstrated in the literature. The objective of this study was to evaluate corn yield response to application of starter P fertilizer to soils with varying M3P concentrations. This study was conducted at three locations in Maryland where, following 14 yr of phytoremediation by continuous cropping and no P applications, M3P concentrations ranged from 34 to 237 mg kg–1 in soil samples collected from plots prior to study commencement. Beginning in 2015, half of each main plot received inorganic P application prior to corn planting in 3 yr, with corn yield measured in each split plot in each year. We observed no interaction effect of starter P fertilizer and soil P category on corn yield at any location. When the data were analyzed by site‐year, we observed no interaction effect, an effect of soil P category in 5 of 9 site‐years, and a yield response to starter fertilizer in 2 of 9 site‐years, with a positive yield response in 1 site‐year and a negative yield response in the other. Based on these results, we do not recommend Mid‐Atlantic farmers invest in starter P fertilization for corn grown on Coastal Plain soils when not recommended by soil testing.

Effect of sulphur nutrition on growth parameters, yield parameters, yield, nutrient uptake, quality and economics of maize: A review

Maize, queen of cereals is a nutrient exhaustive crop and sensitive to sulphur deficiency. Sulphur deficiency in corn results in interveinal chlorosis, yellowing of younger leaves, reddening of stems and leaves. Sulphur is the fourth major plant nutrient next to nitrogen, phosphorus and potassium. It plays a prominent role in formation of chlorophyll, proteins, oil synthesis and biosynthesis of proteins. Sulphur has significant role in growth parameters, yield attributes and yield of maize crop. The uptake of primary nutrients and efficiency of applied fertilizers were seriously influenced by sulphur availability. Sustaining higher yield is not possible under sulphur deficiency. The investigations carried out by eminent research scientist in maize has shown positive impact and application of 45 to 60 kg ha-1 of sulphur gave maximum growth, yield attributes, nutrient uptake, yield and quality parameters. The present paper is a panoramic view of sulphur nutrition in maize from results of different researchers.

An Inverse Correlation between Corn Temperature and Nitrogen Stress: A Field Case Study

Nitrogen is one of the most important yield‐limiting nutrients for corn (Zea mays). The ability of thermal remote sensing to detect nitrogen deficiency in corn may enable precision agriculture to modify nitrogen rates according to field conditions. This study applies the exergy destruction principle as a theory to explain the inverse relationship between surface temperature and nitrogen rate. Two hypotheses were developed. First, it was hypothesized that agricultural crops experiencing greater growth and providing greater yield will have lower surface temperature. The second hypothesis was that corn grown under optimum levels of nitrogen will have lower surface temperatures compared to corn grown under nitrogen stressed conditions. Field studies were conducted during two summer seasons (2016 and 2017) on an established long‐term field trial of corn yield response to varying rates of nitrogen. It was found that corn surface temperature decreased as the rate of nitrogen increased. A shallow but statistically significant (P < 0.05) negative slope was observed consistently with increasing rates of nitrogen. Surface temperature measurements, however, were variable. This variability was the result of external and weather dependent variables that influenced leaf surface temperature. Despite this variability, the exergy destruction principle provides a theory from which thermal remote sensing can be applied through the use of surface temperature measurements to detect physiological stress in crop plants.Core Ideas Thermal remote sensing was proposed to detect nitrogen stress in corn plants. Nitrogen stressed plants had higher surface temperatures than less stressed plants. Temperature trends were consistent with the exergy destruction principle. Nitrogen‐temperature correlations were statistically significant at the 0.05 significance level. Corn yield increases with nitrogen rate increase and surface temperature decrease.

Predicting Early Season Nitrogen Rates of Corn Using Indicator Crops

Core Ideas Early season N deficiencies in corn are hard to recognize, or they appear later in the season, and are too late to correct the deficiency. Indicator crop growing over the winter and early spring cycle makes perfect sense in terms of being able to detect N deficiencies earlier in the growing season. Indicator crop concept could apply to other cereals and potentially cover crops. Use of optical reflectance sensors has proven to determine optimum N fertilizer requirements and direct in‐season N fertilizer applications. However, corn (Zea mays L.) producer adoption of this technology has been slow due to limited time to determine N deficiencies and apply N fertilizer in‐season. A study was established in north‐central Oklahoma to investigate the N fertilizer response of winter wheat (Triticum aestivum L.) and spring barley (Hordeum vulgare L.) as indicator crops with N fertilizer applied at sufficient (168 kg N ha−1) and zero N rates and to estimate optimal early season N fertilizer application rates of the subsequent corn crop. In the spring, corn was planted adjacent to the indicator crops and harvested to determine the agronomic optimum N rates at 100 and 95% of optimum yield and response of N fertilizer at harvest (RIHarvest). In‐season response of the indicator crops was determined using the normalized difference vegetative index (RINDVI) and was used to provide input values to calculate the algorithm N recommendations of the corn crop. Data analysis determined that positive relationships, though not significant, were observed between RIHarvest and RINDVI at Feekes 5/6 and 7 in wheat and Feekes growth stage 5 of barley. Significant relationships between optimum N rates and algorithm N recommendations were observed; however, the slopes of the relationships were negative, which was not to be expected. The potential of indicator crops to predict the early season response of corn to N fertilizer is unique and could help refine N management strategies.

Evidence for the Ability of Active‐Optical Sensors to Detect Sulfur Deficiency in Corn

Prediction of S deficiency is difficult due to poor soil test relationship to crop response. The purpose of this article is to provide evidence that the use of an N‐sufficient area established for use as a standard for active‐optical (AO) sensor directed in‐season N application could also serve to detect S deficiency in corn (Zea mays L.). Nitrogen rate experiments at Oakes and Arthur, ND, exhibited corn upper‐leaf yellowing in high N treatments while control treatments (0 N) were greenest. Two AO sensors were utilized to record red normalized differential vegetation index (NDVI) and red edge NDVI values. The high‐N treatment had the lowest NDVI readings, and the control treatments had the highest NDVI readings. Within 24 h, an application of gypsum containing 22 kg S ha−1 was applied. Seven days following S application, the sites were revisited. The AO sensors were again used to record red NDVI and red edge NDVI. At both sites, the high N treatment had the highest NDVI readings and the control treatment had the lowest NDVI readings. These experiments indicate that high N treatment can increase the severity of S deficiency in corn. If a lower NDVI reading is recorded in a high N application area than in the surrounding area, S deficiency may be present.Core Ideas Sulfur deficiency in corn is difficult to anticipate using soil analysis. When N availability is low, the affect of S deficiency in corn is minimized. When N availability is high, the affect of S deficiency is intensified. Active‐optical sensors can be used along with an N‐sufficient area to reveal S deficiency.

Influence of sulfur deficiency on chlorophyll‐meter readings of corn leaves

AbstractSulfur (S)‐diagnostic tools are essential for rational use of S fertilizers. There is little information about the suitability of leaf greenness intensity to detect S deficiency in corn (Zea mays L.). This work evaluates, under controlled S‐stressed conditions, (1) the performance of leaf greenness intensity as an indicator of the degree of S deficiency in corn, and (2) the advantage of the upper leaves in relation to the middle leaves for S‐deficiency determination. A pot experiment using sand as growth medium was conducted in greenhouse with corn at S rates of 0, 5, 10, 20, and 40 mg kg–1 and sufficiency of other nutrients. Measurements of aboveground biomass (AB), total nitrogen (N), and S concentrations, and chlorophyll‐meter readings (CMR) in upper and middle leaves, were performed at the growth stages of 6–7, 11–12, and 14–15 fully expanded leaves (V6‐V7, V11‐V12, and V14‐V15, respectively). Sulfur application significantly increased AB, leaf S concentration, and CMR. Significantly positive relationships were obtained between leaf S concentration and CMR. A sulfur‐sufficiency index (SSI) based on CMR measured in upper and middle leaves was significantly associated with AB (R2 = 0.58 and 0.62 for the middle and upper leaves, respectively). It is concluded that under sufficiency of other nutrients and high‐S‐stressed conditions, leaf greenness intensity could be a good indicator of corn S status, although little or no advantage was found for taking CMR from the upper leaves.

Shadow effect on multi-spectral image for detection of nitrogen deficiency in corn

The efficiency of side-dressing, a more efficient of nitrogen application method than uniform application in either late Fall or early Spring, relies heavily on the capability of nitrogen deficiency detection on a sprayer. To determine the site-specific yield potential for corn, multi-spectral image analysis including aerial- and ground-based images has been used. Some acceptable calibration relationships between the multi-spectral reflectance and SPAD readings have been found from previous study. In sunny weather conditions there was a shadow in the image made by corn leaf itself. This research investigated the shadow effect on the image for detecting corn nitrogen deficiency based on corn canopy reflectance information. The results indicated that the reflectance of red channel in shadow area showed strong inverse correlation, so the vegetation index NDVI using red and NIR channels also showed strong correlation (R2=77) compared to the whole leaf and bright area. And the reflectance (green and red) and vegetation index(G_NDVI, NDVI, and ratio) in shadow area showed more consistent correlations than others using these image analysis methods.

Potassium nutrient status of corn declined in white clover living mulch

We conducted a field experiment to investigate the effects of white clover living mulch on potassium (K) nutrition and the yield of silage corn. We used a randomized block design with a 2 × 3 factorial arrangement of cropping system and K application treatments. The cropping system treatments were: (1) a white clover living mulch (LM) that had been established 10 months earlier, (2) conventional cultivation with no cover crop (CC). The K application treatments were: (1) no K application (K−), (2) K application at sowing of white clover (Kclover), (3) K application at sowing of corn (Kcorn). In the LM treatments, white clover was sown in August 2006. Corn was sown in June 2007. Before the corn was sown, the white clover shoots in the LM treatments were clipped. The three conventional cultivation treatments were then tilled and corn was sown in all treatments using a minimum tillage seeder. In the LM K) treatment, we observed symptoms of K deficiency in corn leaves on 23 July. At the silking stage of corn, the K and N contents of ear leaves in the LM treatments were significantly lower than those in the conventional cultivation treatments. In the LM K− treatment the K content of ear leaves was <1% and the yield of corn shoots was less than that recorded in the other treatments. Multiple regression analyses revealed that K was the nutrient most strongly related to corn yield. These results suggested that white clover LM declined the K nutrient status of corn and as a result decreased the yield of corn.

INFLUÊNCIA DA DIREÇÃO DA SEMEADURA E DA HORA DO DIA EM ÍNDICES DE VEGETAÇÃO

A necessidade de nitrogênio (N) apresenta grande variabilidade espacial dentro de uma mesma área. A aplicação da real necessidade de N pode aumentar o rendimento, reduzir a aplicação desnecessária e o fluxo para os lençóis freáticos. A medida da reflectância espectral e conseqüente cálculo de índices de vegetação são considerados promissoras abordagens não destrutivas e sem contato para o sensoriamento instantâneo da deficiência de N em milho. Neste trabalho procurou-se estudar a influência da direção da semeadura e da hora do dia nos índices de vegetação no milho. As linhas de semeadura foram localizadas na direção Norte-Sul (NS) e Leste-Oeste (LO). O direcionamento da semeadura em relação à trajetória do sol influenciou os índices estudados: relação infravermelho próximo pelo vermelho - IVP/Verm, índice de vegetação da diferença normalizada - IVDN, índice de vegetação ajustado ao solo - SAVI , índice de vegetação ajustado ao solo aperfeiçoado – OSAVI, relação infravermelho próximo pelo verde - IVP/Verd, índice verde de vegetação da diferença normalizada - IVVDN. O IVVDN apresentou-se mais homogêneo e com menor coeficiente de variação, mostrando-se mais interessante na utilização da aplicação de N em tempo real e a taxas variáveis quando não for possível controlar a direção da semeadura. Caso contrário os índices SAVI e OSAVI são os mais indicados por apresentarem modelos com maior R2.

Temporal Patterns in Symptoms of Nitrogen Deficiency as Revealed by Remote Sensing of Corn Canopy

To evaluate the temporal patterns of N deficiencies in corn and assess the ability of remote sensing to diagnose N deficiencies during the vegetative growth of corn, three field-scale experiments were conducted with various rates (56, 112, and 168 kg N ha −1), timing (early and late applications) and placement (injected into soil and dribbled on soil surface) of N fertilization in a split-plot design. Relationships between canopy reflectance during the growing season and yield data at the end of growing season were studied for different treatments. Results showed significant variation in both grain yields and canopy reflectance among the three cornfields. The N fertilization made in early June resulted in low canopy reflectance in early July, but the differences disappeared as the season progressed. The effect of N rates on canopy reflectance was not significant in early July but it gradually became detectable in mid-July and thereafter. The fertilizer placement had a significant effect on grain yields only in one field but not on canopy reflectance in all three fields. These observations suggest that the deficiency of N developed under field conditions is a dynamic phenomenon, which adds complexity for accurately defining “N deficiency” and effectively developing management strategies for in-season correction. Remote sensing throughout the season helps collect information about important interactions that have not been given enough attention in the past.

Critical Soil Zinc Deficiency Concentration and Tissue Iron: Zinc Ratio as a Diagnostic Tool for Prediction of Zinc Deficiency in Corn

ABSTRACT Zinc (Zn) fertilizer application is most economic if based on soil test and plant analysis information. The aim of this study was to determine the soil test [diethylenetrinitrilopentaacetate (DTPA) and ethylenetriaminepentaacetic acid (EDTA) extractable] Zn-critical levels and tissue Fe/Zn ratio for corn (Zea mays L.). A greenhouse experiment with 12 soil series and two Zn fertilizer treatments (0 and 15 mg Zn kg−1 as zinc sulfate) was conducted. Critical Zn deficiency levels were determined using the Cate-Nelson procedure. Relative corn yield varied from 0.59 to 1.64. Critical deficiency levels based on the Cate-Nelson method were 1.50 and 1.17 mg kg−1 for DTPA and EDTA-extracted soil Zn, respectively. No accurate critical deficiency level could be established using the shoot Zn concentrations. The critical iron (Fe)/Zn ratio in the corn shoot was 3.9. Values greater than 3.9 indicate hidden Zn deficiency and probable response to applied Zn.

Characterization of Corn Nitrogen Status with a Greenness Index under Different Availability of Sulfur

Several methodologies measure leaf greenness intensity and relate it to crop N status. There is no evidence, however, of the utility of this variable to detect N deficiencies in corn (Zea mays L.) under S deficiency. The objective of this work was to evaluate the potential of two indexes based on leaf greenness intensity to detect N deficiencies in corn under different levels of S. Two experiments at Balcarce, Argentina (Bce I and Bce II), and one at 9 de Julio, Argentina (9dJ), were conducted during the 2005–2006 and 2006–2007 seasons with different levels of N and S. Weekly measurements of greenness index (GI) were performed, and whole‐plant samples were taken at four developmental stages to determine crop N and S accumulation. No N × S interaction was found in any measured variable. Nitrogen increased dry matter N and S accumulation, grain yield, and GI. Sulfur fertilization resulted in increased S accumulation in all experiments, and grain yield at Bce II and 9dJ. This nutrient also increased GI during several crop stages in all experiments. A nitrogen sufficiency index (NSI) was related to its relative yield (R2: 0.67, 0.63, 0.43, 0.67 for stages V5–V8, V9–V11, V13–V14, and V15–V18, respectively) under different S levels. On the other hand, a new index called relative greenness index (RGI), proposed for situations that could present S deficiencies, was also related to its relative yield (R2: 0.67, 0.81, 0.63, 0.82 for stages V5–V8, V9–V11, V13–V14, and V15–V18, respectively) under different S levels. The regression lines of both indexes were coincident for all sample dates. It was concluded that crop N status can be characterized under different levels of S through the NSI. Future research, however, should test these results under a wider range of S levels.

Luxury Production of Leaf Chlorophyll and Mid‐Season Recovery from Nitrogen Deficiencies in Corn

Deficiencies of N during the growth of corn (Zea mays L.) are often diagnosed by using chlorophyll meters that measure chlorophyll content in leaves. The diagnoses are based on the assumption that above‐optimal supplies of N do not significantly influence chlorophyll meter readings (CMRs). The objective of this research was to assess the possibility that above‐optimal supplies of N impacted chlorophyll concentration and the effects imposed a limitation on the minimum N deficiencies that can be detected by chlorophyll meters. Our approach was to monitor temporal patterns in CMRs of nonirrigated corn that received various rates of N at various times. The results showed that the time at which N deficiency symptoms first become detectable was closely related to the amounts by which N rates fell short for maximizing grain yield. The measured symptoms of N deficiency changed with time. Temporal patterns in CMRs were affected by N treatments while yields were not greatly affected. In‐season N applications made to plants that started to show N deficiencies caused CMRs to converge with those taken on plants that always had adequate N. These observations suggest that above‐optimal supplies of N may induce a luxury production of chlorophyll that is analogous to luxury uptake of nutrients. These problems severely limit the value of using chlorophyll meters to guide in‐season fertilization in fields having near‐optimal supplies of N. The underlying problem is the uncertainty caused by difficulties associated with distinguishing luxury production of chlorophyll from symptoms of N deficiencies.

Sensitivity of Chlorophyll Meters for Diagnosing Nitrogen Deficiencies of Corn in Production Agriculture

Chlorophyll meters have been widely used to diagnose N deficiencies in research trials and to help refine N fertilizer recommendations in production agriculture. The diagnoses are based on the assumption that chlorophyll meters can detect a wide range of N deficiencies under field conditions according to relationships between chlorophyll meter readings (CMRs) and yield responses to N fertilization that are established from small‐plot trials. We conducted a field‐scale study to evaluate the sensitivity of chlorophyll meters when they are used to detect N deficiencies in corn (Zea mays L.) production. The multiple year–location data were gathered in three cornfields where N fertilizer was applied at different rates in strips that crossed several soil map units. Grain yields were related to CMRs taken on corn leaves in June, July, and August of 1998–1999. Results showed that the chlorophyll meters could detect severe N deficiencies early in the season, but small and moderate deficiencies of N could not be diagnosed with reasonable certainty until it was too late to make in‐season fertilization. Two types of discontinuity are discussed in this paper as likely causes for the limited sensitivity of the chlorophyll meters. Our study suggests that problems associated with the use of chlorophyll meters to diagnose deficiencies of N in production agriculture are much greater than their use to help interpret results of well‐controlled research trials where yields are also measured.

Fertilizer-Induced Advances in Corn Growth Stage and Quantitative Definitions of Nitrogen Deficiencies

Evidence that nitrogen (N) fertilization tends to accelerate maturation as well as increase rates of growth has received little attention when diagnosing N deficiencies in corn ( Zea mays L.). Such a tendency could be a potential source of errors when the diagnosis is solely based on comparing plants with different rates of growth. Whether N fertilization could accelerate rates of growth and maturation was tested in a field study with 12 paired plots representing relatively large variability in soil properties and landscape positions. The plots were located under conditions where preplant N fertilization reduced or avoided temporary N shortages for some plants but did not reduce for other plants early in the season. We measured corn heights to the youngest leaf collar, stages of growth and chlorophyll meter readings (CMRs). The added N advanced growth stages as well as increased corn heights and CMRs at any given time. Fertilization effects on corn heights, growth stages and ear weights were statistically significant ( P < 0.05) despite substantial variability associated with landscape. Reductions in growth due to a temporary shortage of N within a growth stage might be partially offset by longer periods of growth within that stage to physiological maturity. Temporary shortages of N, therefore, may produce symptoms of N deficiency in situations where subsequent additions of N should not be expected to increase yields. Recognition of these two somewhat different effects (i.e., increase growth rates and advance growth stages) on corn growth could help to define N deficiency more precisely and to improve the accuracy of diagnosing N status in production agriculture.

Reduction–Oxidation Effects on Soil Potassium and Plant Uptake

Potassium ions (K+) may become “fixed” between adjacent phyllosilicate layers under waterlogged conditions, rendering K less available to plant uptake. This phenomenon was investigated under greenhouse conditions to determine if K fixation due to biogeochemical reduction contributed to the K deficiency in corn (Zea mays L.) in the northern Great Plains (South Dakota). The objective of this study was to evaluate the effects of a single reduction–oxidation (redox) event on soil K fractions and plant K uptake in montmorillonitic soils. Surface soil (Udolls, 0–15 cm) was collected from various sites across east-central South Dakota and used in a completely randomized greenhouse pot study ( 2×4 factorial). Reduced (Re) and reduced/reoxidized (Re/Ox) treatments were established, and corn was grown to the V5 stage of growth in a two cropping sequence. Potassium levels among soil K fractions did not significantly change upon the redox event. Dry matter (DM) yields were not significantly affected by the redox event. Cumulative K-uptake ranged from 25.7 to 33.2 mg K (kg soil−1), and there were no significant differences between treatments. No increase in K fixation was observed as the result of a single reduction–oxidation event. A single redox event does not cause K fixation in four montmorillonitic soils studied under greenhouse conditions.

Correcting Iron Deficiency in Corn with Seed Row–Applied Iron Sulfate

Corn (Zea mays L.) grown on calcareous, high-pH soils is susceptible to Fe deficiency, which can reduce grain yield by as much as 20%. The objective of this study was to evaluate several treatments of FeSO4 that could be used with precision-farming technologies to alleviate Fe deficiency in irrigated corn. Three sites in 1999 and four in 2000 were selected (based on a history of Fe deficiency) for small-plot (3 by 12.2 m) studies in western Kansas. In 1999, five treatments, including four rates of FeSO4·H2O (0–81 kg ha−1 product) applied in the seed row and one foliar treatment (chelated Fe), were evaluated. In 2000, two additional treatments, CaSO4·2H2O (85 kg ha−1 product) and liquid FeSO4·7H2O (91 kg ha−1 product) applied in the seed row, were included. Grain yield increased linearly with increasing rates of FeSO4·H2O at four of seven site-years, increasing 0.02 Mg ha−1 for each kilogram per hectare of FeSO4·H2O applied. Based on yield responses observed in this study, 81 kg ha−1 FeSO4·H2O was the most consistent treatment for correcting Fe deficiency in corn. If the average yield response obtained in this study can be achieved on 15% of an individual cornfield, the expected return would be $3.00 ha−1 for the entire field. Current precision-farming technologies allow application of FeSO4·H2O only to areas susceptible to Fe deficiency. Employing these technologies provides a practical solution to the spatial heterogeneity of Fe deficiency in irrigated corn and increases the probability of crop response to the fertilizer application.

Correcting Iron Deficiency in Corn with Seed Row–Applied Iron Sulfate

Corn (Zea mays L.) grown on calcareous, high‐pH soils is susceptible to Fe deficiency, which can reduce grain yield by as much as 20%. The objective of this study was to evaluate several treatments of FeSO4 that could be used with precision‐farming technologies to alleviate Fe deficiency in irrigated corn. Three sites in 1999 and four in 2000 were selected (based on a history of Fe deficiency) for small‐plot (3 by 12.2 m) studies in western Kansas. In 1999, five treatments, including four rates of FeSO4·H2O (0–81 kg ha−1 product) applied in the seed row and one foliar treatment (chelated Fe), were evaluated. In 2000, two additional treatments, CaSO4·2H2O (85 kg ha−1 product) and liquid FeSO4·7H2O (91 kg ha−1 product) applied in the seed row, were included. Grain yield increased linearly with increasing rates of FeSO4·H2O at four of seven site‐years, increasing 0.02 Mg ha−1 for each kilogram per hectare of FeSO4·H2O applied. Based on yield responses observed in this study, 81 kg ha−1 FeSO4·H2O was the most consistent treatment for correcting Fe deficiency in corn. If the average yield response obtained in this study can be achieved on 15% of an individual cornfield, the expected return would be $3.00 ha−1 for the entire field. Current precision‐farming technologies allow application of FeSO4·H2O only to areas susceptible to Fe deficiency. Employing these technologies provides a practical solution to the spatial heterogeneity of Fe deficiency in irrigated corn and increases the probability of crop response to the fertilizer application.