Soil Science Masters Theses

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Redistribution and fate of applied ¹⁵N-enriched urea under irrigated continuous corn production
(North Dakota State University, 1996) Schindler, Frank Vincent
Understanding the redistribution and fate of N is essential for justification of Best Management Practices (BMP). This project was conducted on a Hecla fine sandy loam (sandy, mixed, Aquic Haploboroll) soil at the BMP field site near Oakes, North Dakota. One objective of this investigation was to evaluate the residence times of N03- -N in 20 undisturbed lysimeters and its infiltration time through the soil profile to tile drains. Corn (Zea mays L.) was fertilized with 135 kg N ha -1 as ¹⁵N-enriched urea plus 13.5 and 48.1 kg N ha -1 preplant for 1993 and 1994, respectively. Urea-N was band applied to 20 and 10 undisturbed lysimeters at 2.0 and 5.93 atom percent (at %) ¹⁵N in 1993 and 1994, respectively. Average resident times of N03- -N in the lysimeters was 11.7 months. Lysimeter and tile drainage indicate the presence of preferential pathways. Residence times of N03- -N depend on frequency and intensity of precipitation events. Another objective was to determine what portion of the total N in the crop was from applied urea-N and what portion was from the native soil-N. Nitrogen plots received ¹⁵N enrichments of 4.25 and 5.93 at % ¹⁵N in 1993 and 1994, respectively. At the end of the 1993 and 1994 growing season, 41.5% and 35.7% of the labeled fertilizer N remained in the soil profile, while the total recovery of applied ¹⁵N in the soil-plant system was 86.2% and 75.4%, respectively. Low recoveries of applied N may have been the result of soil or aboveground plant biomass volatilization, or denitrification or preferential flow processes. Further research needs to be conducted with strict accountability of gaseous loss and the mechanism(s) responsible.
An Evaluation of Electrical Conductivity Meters for Making In-Field Soil Salinity Measurements
(North Dakota State University, 2010) Briese, Lee Galen
Soil electrical conductivity (EC) can be used as a parameter to assist agricultural producers in making economically important management decisions. Since particular crops and crop varieties respond dynamically to soluble salt levels in relation to crop growth stage and soil moisture content, many management decisions regarding crop type and variety must be made prior to planting. Some crop stress factors could be removed or mitigated if a handheld EC meter could be implemented during the growing season. The objectives of this research were to 1) determine the accuracy of four handheld EC meters for measuring soil EC across a range of environmental temperatures of 15, 20 and 25° C, soil clay concentrations of 10.2, 17.8, 19.3, 32.3 and 50.4 %, and salt solutions containing NaMg- SO4 or Na-Mg-Cl at concentrations of approximately 0, 1, 2, 4 and 8 dS m-1 under controlled laboratory conditions; 2) identify functional differences of the meters that might pose problems for in-field use; and 3) determine if meter price is related to accuracy. The EC values provided by three of the handheld EC meters were significantly different than the standard meter at all treatment levels. Measurements at different temperatures of the standard KCI calibration solution (known EC 1.413 dS m ·1 ) varied by ±0.15, -0.01 to +0.16, -0.14 to -0.03, and ±0.03 dS m-1, for the Hanna Black (Hl993310), Hanna Blue {Hl98331), Field Scout, and SenslON 5 meters, respectively. When salinity was 3 dS m-1 or greater the difference between the test meters and standard meter (EC Response} was larger. Test meter measurements for the salinity by clay interaction were different than the standard meter by ±0.5, ±1, and -2.5 to +1.5 dS m-1, for EC levels of less than 3, 3 to 4, and greater than 4 dS m-1, respectively. The SenslON 5 handheld was the only meter tested that was not significantly different than the standard meter {p::; 0.48}. Test meter accuracy was highly dependent on temperature. Therefore, the most important criteria for selecting a portable meter for in-field EC measurements is the accuracy of the specific meter's temperature measurement and temperature compensation model.
Shifting Perspectives: Desocialization and the Journey Toward Critical Consciousness
(North Dakota State University, 2010) Mathers, Angela Marie
The purpose of this study was to investigate how a service-learning course fosters students' development of a critical consciousness. Participants of this research study were students who participated in the 2009 International Service Seminar, a three-credit course that culminated with a service trip to Antigua, Guatemala. Interviews were conducted with participants that focused on students' experiences both during the class and in the year since the completion of the course. Utilizing critical pedagogy literature, I focused on the work of Jennifer Moon (1999) and Ira Shor (1992) to analyze the processes through which students gain critical consciousness. What became clear in my analysis is that desocialization was a significant component of the process of moving toward critical consciousness. In fact, the highly personal ways in which desocialization was woven into each students' experiences in the course, demonstrated that the journey toward critical consciousness occurs in a jagged manner. Understanding the nature of the desocialization process provides instructors of service learning courses the opportunity to foster critical consciousness in a more successful manner.
The Relative Nitrogen Fixation Rate and Colonization of Arbuscular Mycorrhizal Fungi of Iron Deficient Soybeans
(North Dakota State University, 2011) Podrebarac, Frances Ann
Soybeans (Glycine max L. Merr.) are a symbiont of two beneficial associations: biological nitrogen fixation (BNF) with Bradyrhizobium japonicum, and arbuscular mycorrhizal fungi (AMF). Within the Northern Great Plains of the USA, iron deficiency chlorosis (IDC) of soybean is a yield-limiting factor. The effects of IDC on BNF and AMF are not well defined. This study was conducted to determine the effects of IDC on BNF and AMF. A laboratory study was performed to compare three methods of measuring ureide-N, a product of BNF in soybeans. Field studies in soybean were performed at three locations at eastern N011h Dakota. The experimental design was a factorial combination of three cultivars and three treatments. The three cultivars, in order of decreasing chlorosis susceptibility, were NuTech NT-0886, Roughrider Genetics RG 607, and Syngenta S01-C9 RR. The three treatments were control, Sorghum bicolor L. companion crop planted with the soybean seed, and FeEDDHA applied with the soybean seed. Chlorosis severity was the greatest and least for the NuTech and Syngenta cultivars, respectively. The FeEDDHA treatment decreased chlorosis severity. Ureide levels were abnormally high in plants severely stunted by JDC. The excess accumulation of ureides in IDC-stunted plants suggests that plant growth was reduced more than the rate of nitrogen fixation. The AMF population \vas at an adequate level at all locations and not affected by cultivar or treatment, in general. In the laboratory study, the Patterson et al. method had greater ureide concentrations due to the non-specific measuring of ammonium compounds compared to the Vogels and Van der Drift and Goos methods.
Evaluation of 1:5 Soil to Water Extract Electrical Conductivity Methods and Comparison to Electrical Conductivity of Saturated Paste Extract
(North Dakota State University, 2011) He, Yangbo
Conducting a 1 :5 soil:water extract to measure electrical conductivity (EC) is an approach to assess salinity and is the preferred method used in Australia. However, the influence of salinity on plant growth is predominantly based on saturated paste extract electrical conductivity (ECe) and ECe is recommended as a general method for estimating soil salinity internationally, so it is necessary to convert EC1:s to ECe, The objectives of this research were to 1) compare methods of agitation (shaking plus centrifuging (shaking/centrifuging), shaking, and stirring) for determining EC1: 5; 2) determine optimal times for equilibration for each method across a range of salinity levels determined from saturated paste extracts (ECe) (objectives 1 and 2 are for paper 1); and 3) develop predictive models to convert ECu data to ECe based on four different 1 :5 extraction methods listed above and a USDA-NRCS equilibration technique ( objective 3 is for paper 2). The soils evaluated for the two studies were from north central North Dakota, USA, where 20 soil samples having ECe values ranging from 0.96 to 21 dS m-1were used for the first study (objectives 1 and 2), and 100 samples having ECe values ranging from 0.30 to 17.9 dS m-1were used in the second study (objective 3). In the first study, for each method, nine equilibrium times were used up to 48 hrs. In the second study, a uniform agitation time (8 hrs) was applied to the first three agitation methods, and 1 hr was also used for the USDA-NRCS method. For the first study, significant relationships (p < 0.05) existed between values ofEC1:s and agitation time across the three methods. Agitation methods were significantly different (p S 0.05) from each other for 65% of the soils and shaking/centrifuging was significantly different (p < 0.05) from stirring for all soils. In addition, for 75% of the soils, shaking/centrifuging was significantly different (p :S 0.05) from shaking. Based on these results, methods were analyzed separately for optimal equilibration times. The agitation times required for the three methods to reach 95 and 98% of equilibration were a function of the level of soil salinity. For soils with ECe values less than 4 dS m·1, over 24 hrs was needed to obtain both 95 and 98% of equilibration for the three methods. However, less than 3 and 8 hrs were needed to reach 95 and 98% equilibration, respectively, across methods for soils having ECe values greater than 4 dS m·1. These results indicate that establishing a standard method is necessary to help reduce variation across EC1:s measurements. In the second study, the value ofECe was highly correlated with EC1:s (p < 0.0001) across four agitation methods in non-transformed, log10- transformed, and dilution ratio models through regression analysis. The values of coefficient of determination (r2 ) were greatly improved and average about 0.87 using log10- transformation compared to other two models (r2 values of about 0.68 for the nontransformed models and 0.69 for the dilution ratio models). Since agitation methods were determined to be highly correlated with each other, any regression model determined under the four agitation methods were applicable for the estimation of ECe from another method. The results from this research indicate that comparing data across studies should be done with caution because both agitation method and time can influence results. Also, estimation ofECe from EC1:5 can be done with confidence, but models may not be transferrable across different soil orders or across various salt types.
Effects of Major Flooding on Water and Sediment Characteristics in an Urban Enviromnent
(North Dakota State University, 2011) Guy, Adam Christopher
Spring flooding of the Red River of the North is a common phenomenon, but no infonnation exits on how these flooding events impact both water and sediment quality within an urban area. The objectives of this study were to assess if urban enviromnents affect floodwater quality and to determine the quality of sediment deposited in an urban environment after floodwaters recede. Water samples were taken on 12 dates from two locations before and after the city limits of Pargo, North Dakota and Moorhead, Minnesota (F-M), and were measured for 12 variables including total sediment, P04, 17/3-estradiol, and diesel range organics. Sediment and underlying soil samples were collected from three locations within F-M where, at each location, there were three equidistant transects parallel to the river channel, and analyzed for 40 variables including dry sediment mass, carbon, nitrogen, diesel and gasoline range organics, and trace elements. Considering river discharge and total sediment and P04 concentrations at each sampling date, about 4500 Mg of sediment and 30 Mg of P04 were estimated to have been deposited within F-M. l 7Bestradiol was detected in 9 of 24 water samples with an average concentration of0.61 ng L1 and diesel range organics were detected in 8 of 24 samples with an average concentration of 80.0 µg L-1. Average mass of sediment across locations and transects ranged from about 2 to 1 O kg m·2 where transects closest to the river channel had the higher mass deposits of sediment. Total carbon and nitrogen within the sediment was determined to be mostly organic and ranged from about 40 to 59 g kg' 1 and about 1,760 to 4,930 mg kg·1, respectively, with the highest concentrations occurring at the transect furthest from the river channel. No gasoline range organics were detected, but diesel range organics were detected in 26 of the 27 sediment samples analyzed with a maximum concentration of 49.2 µg g-1• Total Hg concentrations in the sediment and soil averaged about 55 and 61 ng g-1, respectively, and all trace elements detected in the sediments were within ranges for noncontaminated sites. Although sediments remaining after floodwaters recede can be unsightly and cleanup efforts can be labor intensive, these sediments can also provide essential plant nutrients for urban riverine ecosystems, which may include turf grass, fruits and vegetables, and horticultural plants.
Characterizing Soil Microbial Communities of Reclaimed Roads in North Dakota
(North Dakota State University, 2012) Viall, Eric
Reclaimed roads on the Little Missouri National Grasslands of southwestern North Dakota have not returned to pre-disturbance conditions. Phospholipid fatty acid analysis was performed on soil samples collected from reclaimed roads and adjacent prairie to assess reclamation effects on the microbial community. Additionally, nutrient cycling capacity was measured by four enzyme assays. Ordination analysis of PLFA data identified a distance gradient indicating microbial communities of reclaimed roads were different from the prairie. Specifically, Gram-negative bacteria and arbuscular mycorrhizal fungi are associated with roads; soil organic matter was associated with prairie sites. Soil enzyme activities associated with prairie sites indicate greater nutrient cycling. The soils of reclaimed roads have not accumulated sufficient organic matter to sustain both plant and microbial communities characteristic of the surrounding prairie.
Laboratory and Greenhouse Evaluation of FeEddha Fertilizers of Differing Quality
(North Dakota State University, 2013) Lovas, Sarah
Commercial iron ethylene diamine di(hydroxyl phenyl acetic acid) (FeEDDHA) fertilizers containing the same Fe percent and applied at the same FeEDDHA rate control Fe deficiency chlorosis (IDC) differently due to differing ortho, ortho FeEDDHA (o,o-FeEDDHA) concentrations. This study: 1) determined the effect of o,o-FeEDDHA concentration on controlling IDC in soybeans (Glycine max L. Merr.); and 2) developed a soil-stability test using a simple colorimetric analysis method to determine the relative quality of soil-applied FeEDDHA fertilizers. A greenhouse experiment was conducted where nine FeEDDHA fertilizers were applied at two FeEDDHA rates. The soil-stability test compared these fertilizers with two incubation methods which utilized three soils and four incubation times, and extracts were analyzed by two methods. The results of these experiments suggest that soil-applied FeEDDHA fertilizer quality is contingent upon its o,o-FeEDDHA concentration, and the fertilizer quality can be determined by a soil-stability test with a colorimetric analysis method.
The Use of Sediment Removal to Reduce Phosphorus Levels in Wetland Soils and the Distribution of Plant-Available Phosphorus in Wetland Soils and its Potential Use as a Metric in Wetland Assessment Methods
(North Dakota State University, 2014) Gabel, Skye
Plant-available phosphorus (P) in wetland soils and its relationship with wetland communities and condition is somewhat unknown in the Prairie Pothole Region (PPR) in North America. Research objectives were to determine if 1) sediment removal reduced P in seasonal wetlands; 2) P could be used as an indicator in wetland condition assessments; 3) a gradient in P amount and wetland elevation existed; and 4) differences of sampling and extraction methods change Olsen P results as a metric in assessments. Soil samples from North Dakota wetlands were collected from two depths (0-15 and 15-30 cm) and analyzed for pH, electrical conductivity (EC), and P (Olsen and water-extractable (WEP)). Sediment removal does not reliably reduce P in the shallow marsh zone based on the variability within and between locations. Phosphorus should not be used in wetland assessments, although the shallow marsh zone typically had the most P of the three landscape positions.
Association and Bioavailability of 17β-Estradiol with Soil and Manure Aqueous Dissolved and Colloidal Fractions
(North Dakota State University, 2014) Chambers, Katrin Bella
Steroidal estrogens in the environment exert toxicological effects at very low concentrations. Furthermore, dissolved and colloidal fractions of soil and manure play an important role in the environmental fate and transport of steroidal estrogens. One objective of this study was to quantify the association of the natural estrogen, 17β-estradiol (E2), with the dissolved fraction and colloidal fraction isolated from liquid swine manure (LSM), soil, and soil+LSM mixtures. The second objective of this study was to evaluate whether the E2 associated with the dissolved fraction/colloidal fraction, dissolved fraction and colloidal fraction of the various media could induce an estrogenic response. Estrogenicity was assessed using an E2 receptor (ER) competitor assay, which provided E2 equivalent concentration (EEQ) of dissolved fraction/colloidal fraction, dissolved fraction and colloidal fraction solutions created from the Soil, Soil+LSM and LSM.
Yield and Quality Prediction Using Satellite Passive Imagery and Ground-Based Active Optical Sensors in Sugar Beet, Spring Wheat, Corn, and Sunflower
(North Dakota State University, 2014) Bu, Honggang
Remote sensing is one possible approach for improving crop nitrogen use efficiency to save fertilizer costs, reduce environmental pollution, and improve crop yield and quality. Feasibility and potential of using remote sensing tools to predict crop yields and quality as well as to detect nitrogen requirements, application timing, rate, and places in season were investigated based on a two-year (2012-2013) and four-crop (corn, spring wheat, sugar beet, and sunflower) study. Two ground-based active optical sensors, GreenSeekerTM and Holland Scientific Crop CircleTM, and the RapidEyeTM satellite imagery were used to collect sensing data. Highly significant statistical relationships between INSEY (NDVI normalized by growing degree days) and crop yield and quality indices were found for all crops, indicating that remote sensing tools may be useful for managing in-season crop yield and quality prediction.
Evaluating Dynamic Soil Change in the Barnes Soil Series Across Eastern North Dakota
(North Dakota State University, 2015) Montgomery, Brandon
Quantifying long-term, global soil change is of the utmost importance as the human population continues growing and food security needs intensify. North Dakota presents a unique opportunity to study dynamic soil change because of its agricultural prominence and extensive soil survey data. A resampling method to characterize soil change from legacy soil survey data was utilized on a benchmark soil series, the Barnes, in North Dakota. Significant decreases (p<0.05) in soil organic carbon (SOC) were measured in surface horizons of three Barnes pedons, and depending upon management practices, morphologic changes ranged from highly eroded, with the complete loss of the A horizon, at two sites, to non-eroded conditions at sites returned to CRP 25 years ago. Additionally, using remotely sensed evapotranspiration (ET) data as a non-biased proxy for soil function shows modeling potential. These results serve as a proof of concept and demonstrate the need for more comprehensive research.
Soil Salinity and Sodicity Impacts on Soil Shrinkage, Water Movement and Retention
(North Dakota State University, 2015) Klopp, Hans Walter
Saline, sodic, and saline-sodic ground waters are problematic throughout the Northern Great Plains and Red River Valley. High sodium adsorption ratio (SAR) and low electrical conductivity (EC) of soil solution and irrigation waters are known to create issues with saturated soil hydrologic conductivity. Our objective was determine the impact of saline, sodic and saline-sodic solutions on soil shrinkage and soil hydrologic properties. Soil shrinkage, water retention, and hydraulic conductivity were determined on a variety of soil textures following saturation with salt solutions of variable EC and SAR combinations. Data were fitted with simple theoretical models then model parameters statistically compared. Increasing SAR and decreasing EC of increased soil shrinkage, decreased hydraulic conductivity, and increased water retention near saturated conditions (i.e., > -100 cm H2O). Whereas saline-sodic waters resulted in the greatest rate of decline in saturated conductivity over time such as when salts would be managed without maintaining divalent cations.
The Influence of Soil Salinity Gradients on Soybean [Glycine Max (L.) Merr.] and Corn (Zea Mays L.) Growth
(North Dakota State University, 2015) Langseth, Chandra Marie
An estimated 2.3 million hectares are salt-affected in North Dakota (Brennan and Ulmer, 2010), a number increasing due to land management, climate, and crop choice. As a result, yield reductions are noted for salt-sensitive crops such as soybean [Glycine max (L.) Merr] and corn (Zea Mays L.). The objective of this greenhouse study was to assess soybean and corn response to salinity, using sulfate based salts. Soybean leaf area, plant mass, and height decreased by 66, 59, and 47%, respectively, across a salinity gradient ranging from an EC1:1 of 0.4 to 4.1 dS m-1. Corn mass and height decreased by 42 and 26%, respectively, root length and mass also decreased by 44 and 37%, respectively from an EC1:1 0.8 to 5.3 dS m-1. Thus, planting soybean and corn on salt-affected soils in North Dakota will result in overall decreased productivity for both crops even at low levels of salinity.
Evaluation of Soil Potassium Test to Improve Fertilizer Recommendations for Corn
(North Dakota State University, 2015) Rakkar, Manbir Kaur
A study was conducted at thirteen locations in North Dakota and Minnesota in 2013 and 2014 with the objectives of determining difference between the soil potassium (K) results based upon air-dried (KDry) and field-moist (KMoist) soil samples during the corn growing season and to evaluate corn response to applied K-fertilizer. Overall, KDry tests showed higher K levels in the soil test results compared to KMoist but the pattern of deviation was dependent upon various soil properties such as initial soil K level. Temporal variation of soil K levels indicated a need to consider time of soil sampling while making fertilizer recommendations. Potassium application significantly increased corn yields at only five out of 11 sites with soil K levels below critical K soil test levels (<150 ppm). Therefore, development of an improved soil testing strategy is required to improve the predictability of corn response to applied K fertilizer in this region.
Influence of Amendments on Chemical and Biological Properties of Sodic Soils
(North Dakota State University, 2016) Breker, Maria Christine
Improving productivity of sodic soils has become a concern in North Dakota because of the desire for more land for producing crops. Field and incubation studies were conducted to determine the impacts of different amendments (flue-gas desulfurization gypsum, sugar beet processing by-product lime, and langbeinite) on the chemical and biological properties of two sodic soils. The field study evaluated the amendment effects on the chemical conditions of the soil and the impact on alfalfa yield and quality. Differences were not observed in percent sodium (%Na) in the first 17 months and alfalfa yield was not impacted by the treatments except for the high rate of langbeinite. The incubation study investigated the effects of amendments on both the chemical and biological properties of the soil. Spent lime increased the cumulative respiration but was not impacted by gypsum or langbeinite. Labile carbon (C) was negatively correlated with %Na and electrical conductivity (EC).
Sugarbeet Yield and Quality Response to Nitrogen Fertilizer Rate and In-Season Prediction of Yield and Quality Using Active-Optical Sensor
(North Dakota State University, 2016) Subedi, Keshab
Nitrogen (N) management is one of the important factors in sugarbeet production. Under-application of N-fertilizer results in lower root yield while over-application of N-fertilizer can result in decreased sugar concentration and recoverable sugar. In recent years active-optical sensors have been investigated for in-season prediction of sugarbeet yield and quality and to make N management decisions. This study was conducted at four sites in the Red River Valley to determine the sugarbeet yield and quality response to N fertilizer rates and to determine the relationship of NDVI with sugarbeet yield and quality. The yield response to N fertilizer rates was significantly quadratic, however, sugar concentration did not show response to N fertilizer rates. In-season NDVI readings were strongly related with root yield and sugar yield. Active sensing during the growing seasons shows promise as a means to predict sugarbeet root yield and sugar yield.
Nitrogen and Phosphorus Recalibration for Sunflower in North Dakota
(North Dakota State University, 2016) Schultz, Eric Charles
Sunflower is one of the most important annual crops grown for edible oil in the world and is grown in North Dakota and the northern Great Plains more than any other region in the United States. Sunflower production and sunflower itself has evolved significantly since commercial cultivation began in the 1970s. In order to properly update fertility requirements of nitrogen and phosphorus in the northern Great Plains to correspond to this evolution, sunflower yield and oil concentration response to nitrogen and phosphorus fertilizer was investigated based on a twoyear (2014-2015) study. Highly significant statistical relationships between sunflower yield and oil concentration were found with nitrogen fertilizer rate but were not found with phosphorus fertilizer rate. This indicates that nitrogen fertilizer application rates used for sunflower need to be determined by current documented responses and that phosphorus fertilizer may not be needed to produce optimal yield and oil concentration of sunflower.
Brine-Contaminated Soils in Western North Dakota: Site Assessment Methodology and a New In-Situ Remediation Method
(North Dakota State University, 2016) Klaustermeier, Aaron Wallace
Anthropogenic soil salinity caused by produced water (i.e., brine) contamination is an issue in all oil and gas producing regions. The objectives of this research are to develop soil electrical conductivity (EC) conversion equations for rapid site assessment of brine spills and to determine the efficacy of crystallization inhibitors as an in-situ remediation method. Conversion equations were developed for soil-to-water suspensions and saturated paste extracts (ECe) on brine-contaminated soils. These new equations provided the best prediction of ECe when compared to 14 other equations reported in the literature. A crystallization inhibitor (C18Fe7N18) applied to NaCl-contaminated soils using various concentrations and methods of application yielded dendritic salt crystals above the soil surface. On average, between 0.29 and 0.57 g g-1 of NaCl salts effloresced when surface applying a 0.01M concentration of the crystallization inhibitor. Results from these studies will guide consultants and researchers in the assessment and remediation of brine-contaminated soils.
Foliar Application of Iron Chelated Fertilizer and Surfactants for Management of Iron Deficiency Chlorosis in Soybeans
(North Dakota State University, 2016) Rasmussen, Heidi
Iron deficiency chlorosis (IDC) is a production challenge for farmers growing soybeans [Glycine max (L.) Merr.], especially in the Red River Valley. It is critical to correct this deficiency as soon as symptoms arise before growth, and ultimately yield, is negatively impacted. Field experiments of foliar applied iron fertilizers (o-o-EDDHA, o-o-EDDHSA, HEDTA, and an amino acid) and suitable adjuvants (HSOC [high surfactant oil concentrate], non-ionic surfactant, acidifier, and organosilicone surfactant), to control IDC were conducted during the 2013 and 2014 growing seasons, respectively. There was high variability among the results for both the SPAD meter readings and soil iron concentration. The yield values were greater in the treated plots than with control plots, but not significantly so. Further experiments should be conducted to gain more knowledge on the prolonged use and efficiency of these products in the correction of IDC.

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