Defining Yield Goals and Management Zones to Minimize Yield and Nitrogen and Phosphorus Fertilizer Recommendation Errors

Three general approaches (minimize soil nutrient variability, yield, and fertilizer recommendation errors) have been used to assess nutrient management zone boundaries. The objective of this study was to determine the influence of different approaches to define management zones and yield goals on minimizing yield variability and fertilizer recommendation errors. This study used soil nutrient and yield information collected from two east-central South Dakota fields between 1995 and 2000. The crop rotation was corn (Zea mays L.) followed by soybean [Glycine max (L.) Merr.]. The four management zone delineation approaches tested were to: (i) sample areas impacted by old homesteads separately from the rest of the field; (ii) separate the field into grid cells; (iii) use geographic information systems or cluster analysis of apparent electrical conductivity, elevation, aspect, and connectedness to identify zones; and (iv) use the Order 1 soil survey. South Dakota fertilizer N and P recommendations were used to calculate fertilizer requirements. This study showed that management zones based on a 4-ha grid cell and an Order 1 soil survey had lower within-zone yield variability than the other methods tested. The best approaches for minimizing recommendation errors were nutrient specific. Nitrogen and P recommendations were improved using multiple years of yield monitor data to develop landscape-specific yield goals, sampling old homesteads separately from the rest of the field, and grid cell soil sampling to fine-tune N and P recommendations

Chemical Amendments of Dryland Saline–Sodic Soils Did Not Enhance Productivity and Soil Health in Fields without Effective Drainage

A common restoration treatment for saline–sodic soils involves improving soil drainage, applying soil amendments (e.g., CaSO4, CaCl2, or elemental S), and leaching with water that has a relatively low electrical conductivity. However, due to high subsoil bulk densities and low drainable porosities, these treatments many not be effective in glaciated dryland systems. A 3-yr field study conducted in three model systems determined the impact of chemical amendments (none, CaCl2, CaSO4, and elemental S) on plant growth, microbial composition, temporal changes in electrical conductivity (ECe ), and the relative sodium content (%Na). Chemical amendments (i) either reduced or did not increase maize (Zea mays), soybean (Glycine max), and sorghum (Sorghum bicolor) yields; (ii) did not increase water infiltration or microbial biomass as determined using the phospholipid-derived fatty acid (PLFA) technique; and (iii) did not reduce ECe or %Na. These results were attributed to high bulk densities and low drainable porosities that reducing the drainage effectiveness in the model backslope and footslope soils, the presence of subsurface marine sediments that provided a source for sodium and other salts that could be transported through capillary action to the surface soil, high sulfate and gypsum contents in the surface soil, and relatively low microbial biomass values. The results suggests that an alternative multistep saline sodic soil restoration approach that involves increasing exchangeable Ca+2 through enhanced microbial and root respiration and increasing transpiration and soil drainage by seeding full season deep rooted perennial vegetation should be tested

Nitrogen and Water Stress Impacts Hard Red Spring Wheat (Triticum aestivum) Canopy Reflectance

Remote sensing has been proposed as a method for implementing an inseason spring wheat (Triticum aestivum) nitrogen (N) fertilization program. However, in fields where yields are influenced by both water and N stress, accurate N recommendations require that that the N and water stress signals be separated from each other. The objective of this study was to determine the impact of water and N stress on canopy reflectance and the ability of vegetation (NDVI, GNDVI, and BNDVI), and chlorophyll (CGreen and CRedEdge) indices to separate water and N stress. A split-plot experiment containing four blocks was conducted in 2002, 2003, and 2005 at Aurora South Dakota. The treatments were two soil moisture regimes and four N rates. Canopy reflectance was measured with a handheld multispectral radiometer at Haun 2, 4-4.5, 6, and 10-10.2. Canopy reflectance was measured in 16 different bands. Remote sensing-based prediction models for yield, yield loss due to N stress, yield loss for water stress, and protein were developed. Yield loss due to N stress decreased with increasing N, while yield loss to water stress had the opposite relationship. Protein concentration generally increased with N. The remote sensing models for protein and yield loss due to N stress explained more of the variability than the yield model at Haun 4-4.5 and Haun 6. These data suggest that canopy reflectance can be used to separate N and water stress signals in hard red spring wheat

Calculating Soil Organic Turnover at Different Landscape Position in Precision Conservation

An important aspect of precision conservation is assessing changes in soil health and soil organic carbon (SOC) across landscapes. Carbon (C) cycling can be determined using carbon flux towers, modeling, and by experimentally measuring budgets. Once the carbon budgets are understood, this information can be used to assess the value of implementing precision conservation and the potential impacts of targeted residue harvesting on soil health. This chapter provides a review of methods to determine carbon budgets, and the potential impacts of crop residue harvesting on SOC maintenance across landscapes. The chapter also provides examples on how to convert point carbon budget measurements into a precision conservation assessment

Corn Yield Is Not Reduced by Mid-Season Establishment of Cover Crops in Northern Great Plains Environments

In northern climates, establishment of fall cover crops after corn or soybean harvest is difficult due to cold and dry conditions. This study examined an alternative option: in-season cover crop seeding, timed for plants to emerge just following the critical weed-free period of corn (Zea mays L.) to allow establishment and growth without compromising yield. Crimson clover (Trifolium incarnatum L.), lentil (Lens culinaris Medik.), and winter wheat (Triticum aestivum L.) seed was blended and either drill (DRL) or broadcast (BRD) seeded into corn at the five-leaf (V5; late June) growth stage at three South Dakota sites (7 site years) and at V3 at one site in 2 years. Visual observations in mid-July verified establishment, and aboveground live (e.g., green) biomass was quantified at about R4 (soft dough), prior to corn grain harvest. Cover crop establishment and growth were superior with DRL seeding, which had rapid establishment and more aboveground biomass compared with BRD seeding. Although the total biomass in the V3 and V5 DRL treatments was similar, corn yield was reduced 10% in the V3 seeded plots but was unaffected by V5 seeding. Soil microbial communities were similar to the no-cover-crop control. Our results suggest that cover crops can be established successfully in standing corn at the V5 growth stage without compromising grain yield

Nitrogen and Water Stress Affect Winter Wheat Yield and Dough Quality

Nitrogen recommendations designed to increase wheat (Triticum aestivum L.) yields may diminish wheat quality. By understanding fertility management impacts on quality, it may be possible to optimize N recommendations to sites and climates. The objective of this study was to quantify the combined and individual impacts of N and water stress on winter wheat grain yield, grain protein, dough quality, and water and N use efficiency. A field experiment using five N rates (ranging from 0 to 1.5 times the current university recommendation) and two water levels (adequate and deficient) was conducted in South Dakota in 2007 and 2008. Dough characteristics were measured using a farinograph. In 2007, soil N mineralization was high (192 kg N ha−1), supplemental water increased grain yield and grain N use efficiency (GNUE) by 25% and reduced yield loss due to N stress from 1141 to 480 kg ha−1, whereas relative to 0 N, the recommended N rate increased water use efficiency by 21% and reduced yield loss due to water stress from 737 to 481 kg ha−1. These benefits were achieved without a loss of dough quality. In 2008, N mineralization was low (99 kg N ha−1), water did not impact GNUE, and the adequate water treatment had lower grain protein (12.5 vs. 13.1 g kg−1) and arrival (3.3 vs. 4.3 min) and peak times (6.1 vs. 7.8 min) than the deficient water treatment. These findings suggest that the implementation of strategically applied N fertilizer may require improved estimates of N mineralization

Long QT and Hearing Loss in High-Risk Infants Prospective Study Registry.

The objective of this study is to determine the prevalence of an abnormal electrocardiogram showing a prolonged QTc greater than 450 ms in infants with unilateral or bilateral sensorineural hearing loss. We conducted a prospective study of healthy term infants (≥37 weeks gestational age) who failed their newborn auditory brainstem response hearing screen, were seen by an audiologist and diagnosed as having sensorineural hearing loss during follow-up to 1 year of age. In infants with a diagnosis of hearing loss, we collected a detailed family history and performed an ECG between 2 and 6 months of age. We obtained follow-up for 1 year by calling the parent requesting the hearing and cardiac status of their child. Two of the 40 infants with sensorineural hearing loss (5%) had a QTc greater than 450 ms. Both had mild bilateral hearing loss and genetic testing did not identify a known mutation for long QT syndrome. The remaining 38 infants had QTc intervals of ≤ 450 ms. One patient diagnosed with bilateral severe sensorineural hearing loss had a normal ECG (QTc = 417 ms). Several months after the ECG was performed, the infant\u27s mother contacted the study cardiologist after she learned that the infant\u27s maternal grandmother was diagnosed with a cardiomyopathy and arrhythmias. Genetic testing was recommended even though the child was asymptomatic and was positive for a pathogenic mutation in the KCNQ1 gene. We speculate that molecular genetic testing in infants with hearing loss may become the standard of care rather than targeted electrocardiograms.Clinical Trial Registration NCT02082431 https://www.clinicaltrials.gov/ct2/show/NCT02692521?cond=NCT02692521&rank=1

Winter Cover Crops Impact on Corn Production in Semiarid Regions

Winter cover crops have produced mixed impacts on crop yields in frigid semiarid environments. Our objective was to determine the influence of winter cover crops and landscape positions on corn (Zea mays L.) yield losses due to water and N stress, soil biology, and gene expression. Following wheat (Triticum aestivum L.), cover crop mixtures were drill seeded into three no-till fields. In the following spring, four N fertilizer rates were applied and corn was no-till seeded. The cover crop had fundamentally different impacts on corn yields at Trail City and Andover in 2011. Both sites were water stressed and responded to N fertilizer; however, at Andover 2011 the cover crop reduced corn yields, while at Trail City 2011 the cover crop did not impact yields. The yield reduction at Andover 2011 was attributed to high cover crop production ( \u3e2000 kg ha–1), which reduced soil water 15% in the 30- to 60-cm soil depth in November 2010, and in the following growing season increased corn yield loss due to water stress from 1610 to 2950 kg grain ha–1. Associated with the yield reduction was down expression of two mineral nutrient genes (NCBI, AF325723.1 and APO05869.3) and one gene associated with energy processing (AF325723.1). The cover crops reduced the relative amount of soil NO3 at four of the six landscape positions and increased the relative bacteria/fungi ratio in 2011. These findings indicate that cover crops after winter wheat can be an important mechanism for scavenging N in semiarid frigid environments; however, adopting techniques that generate high cover crop yields can adversely influence the following cash cro