Assessing variation in maize grain nitrogen concentration and its implications for estimating nitrogen balance in the US North Central region

Accurate estimation of nitrogen (N) balance (a measure of potential N losses) in producer fields requires information on grain N concentration (GNC) to estimate grain-N removal, which is rarely measured by producers. The objectives of this study were to (i) examine the degree to which variation in GNC can affect estimation of grain-N removal, (ii) identify major factors influencing GNC, and (iii) develop a predictive model to estimate GNC, analyzing the uncertainty in predicted grain-N removal at field and regional levels. We compiled GNC data from published literature and unpublished databases using explicit criteria to only include experiments that portray the environments and dominant management practices where maize is grown in the US North Central region, which accounts for one-third of global maize production. We assessed GNC variation using regression tree analysis and evaluated the ability of the resulting model to estimate grain-N removal relative to the current approach using a fixed GNC. Across all site-year-treatment cases, GNC averaged 1.15%, ranging from 0.76 to 1.66%. At any given grain yield, GNC varied substantially and resulted in large variation in estimated grain-N removal and N balance. However, compared with GNC, yield differences explained much more variability in grain-N removal. Our regression tree model accounted for 35% of the variation in GNC, and returned physiologically meaningful associations with mean air temperature and water balance in July (i.e., silking) and August (i.e., grain filling), and with N fertilizer rate. The predictive model has a slight advantage over the typical approach based on a fixed GNC for estimating grain-N removal for individual site-years (root mean square error: 17 versus 21 kg N ha−1, respectively). Estimates of grain-N removal with both approaches were more reliable when aggregated at climate-soil domain level relative to estimates for individual site-years

Nitrogen recovery efficiency from urea treated with NSN co-polymer applied to no-till corn

Nitrogen (N) rate increases used by many farmers produce a reduced or null effect on N recovery efficiency (RE) by crops. Therefore, management practices to reduce N losses and increase RE are necessary. Co-polymer maleic itaconic acid (NSN) have become available for use with urea and has shown potential in reducing N losses. The objective of this study was to evaluate the effectiveness of urea treated with NSN on grain yield and RE in a no-till corn. A field experiment was carried out at Balcarce, Argentina over three years, evaluated treatments were urea and urea + NSN at 120 N kg ha− 1, and additional 0 N treatment was included. Urea + NSN was effective to reduce total ammonia volatilization losses, and the average of two years were 1.4 (1.1% to N applied) and 8.7 kg ha− 1 (7.2% to N applied) for urea + NSN and urea, respectively. However, while grain yield and N grain removal were not affected by urea + NSN, the N rate significantly increased grain yield and N grain removal. Nitrogen recovery efficiency was not affected by urea + NSN, RE (average of three years) was 29.0% and 27.8% for urea and urea + NSN, respectively. In conclusion, there was no advantage of using urea treated with NSN in no-till corn overgrain yield, N grain removal, or RE.Fil: Barbieri, Pablo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Sainz Rozas, Hernan Rene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Echeverria, Hernan Eduardo. Universidad Nacional de Mar del Plata. Facultad de Ciencias Agrarias; Argentin

Synthesis and thermoelectric characterization of Bi2Te3 nanoparticles

We report a novel synthesis for near monodisperse, sub-10-nm Bi2Te3 nanoparticles. At first, a new reduction route to bismuth nanoparticles is described which are applied as starting materials in the formation of rhombohedral Bi2Te3 nanoparticles. After ligand removal by a novel hydrazine hydrate etching procedure, the nanoparticle powder is spark plasma sintered to a pellet with preserved crystal grain sizes. Unlike previous works on the properties of Bi2Te3 nanoparticles, the full thermoelectric characterization of such sintered pellets shows a highly reduced thermal conductivity and the same electric conductivity as bulk n-type Bi2Te3.Comment: 8 pages, 8 figures, 1 tabl

Phosphorus Management

Soils with high levels of P can contribute to excess P in runoff and subsequently pollute the surface water. Excess P in the soil can be removed from the system by harvesting crops. The objectives of this study were to evaluate corn (Zea mays L.) P removal effects on soil P reduction, and to evaluate various corn hybrids and soybean [Glycine max (L.) Merr.] varieties for differences in grain P concentration and P removal. Soil with varying P levels as a result of annual or biennial beef cattle (Bos Taurus) feedlot manure or compost application was cropped to corn for 4 yr without any P addition. In other studies under various water and N regimes, corn hybrids and soybean varieties were evaluated for grain P concentration and P removal. Four years of corn production without P addition lowered surface soil (0–15 cm) extractable P level (Bray and Kurtz no. 1) from 265 mg kg-1 to 171 mg kg-1 in the biennial N-based compost treatment. Based on a decay equation, it would have required 10 yr of corn P removal P to lower the soil P level to the original 69 mg kg-1 that existed before treatment application. The rate of decrease in extractable soil P was greater when soil P was higher and reduced with decreasing soil P level. Most of the P in the plants was absorbed from the 0- to 15-cm soil depth since no significant reduction in soil P level was observed from 1996 to 1999 in the 15- to 30-cm soil depth. Across 2 yr, there was as much as 54% difference among corn hybrids for grain P removal. The differences in P concentrations among corn hybrids indicated that hybrids could be selected for low P uptake when P level in ethanol production by-product or in animal ration and subsequently in manure is desired. Soybean grain P concentration was nearly twice that for corn but grain P removal was less for soybean than for corn. Crop P removal can significantly reduce soil P level with time

Recurrence of yield and protein variation in the northern grains region

Grain yield and protein maps of sorghum and wheat were collected over consecutive seasons at Jimbour (southern QLD) and at Gurley (northern NSW) to identify spatial and temporal changes in nitrogen (N) removal and N supply. The Jimbour site was cropped with sorghum for 3 years (1999-2001), and the Gurley site with wheat (1999) then fallowed into sorghum (2001). Grain yield variation was moderate to high; coefficients of variation (CV) ranged from 12 to 30%. Protein variation was low for each site and season with CVs below 10%. At Jimbour, high applications of N fertiliser minimised temporal variation in grain protein. At Gurley, matching of N fertiliser with yield potential (based on soil depth) also resulted in a low temporal variation in protein. The low protein variation, both within seasons and between seasons, then contributed little to the temporal variations in N removal. Both sites had areas of stable variation but low supplies of N; these were related to areas where moisture had pooled or where soil depth, and hence available soil moisture, limited yields. Unstable variation was associated with isolated trees, contour, or edge effects. Under these conditions, protein data may need to only be collected every 2-3 years

Phosphorus Management

Soils with high levels of P can contribute to excess P in runoff and subsequently pollute the surface water. Excess P in the soil can be removed from the system by harvesting crops. The objectives of this study were to evaluate corn (Zea mays L.) P removal effects on soil P reduction, and to evaluate various corn hybrids and soybean [Glycine max (L.) Merr.] varieties for differences in grain P concentration and P removal. Soil with varying P levels as a result of annual or biennial beef cattle (Bos Taurus) feedlot manure or compost application was cropped to corn for 4 yr without any P addition. In other studies under various water and N regimes, corn hybrids and soybean varieties were evaluated for grain P concentration and P removal. Four years of corn production without P addition lowered surface soil (0–15 cm) extractable P level (Bray and Kurtz no. 1) from 265 mg kg-1 to 171 mg kg-1 in the biennial N-based compost treatment. Based on a decay equation, it would have required 10 yr of corn P removal P to lower the soil P level to the original 69 mg kg-1 that existed before treatment application. The rate of decrease in extractable soil P was greater when soil P was higher and reduced with decreasing soil P level. Most of the P in the plants was absorbed from the 0- to 15-cm soil depth since no significant reduction in soil P level was observed from 1996 to 1999 in the 15- to 30-cm soil depth. Across 2 yr, there was as much as 54% difference among corn hybrids for grain P removal. The differences in P concentrations among corn hybrids indicated that hybrids could be selected for low P uptake when P level in ethanol production by-product or in animal ration and subsequently in manure is desired. Soybean grain P concentration was nearly twice that for corn but grain P removal was less for soybean than for corn. Crop P removal can significantly reduce soil P level with time

Multilocation Corn Stover Harvest Effects on Crop Yields and Nutrient Removal

Corn (Zea mays L.) stover was identified as an important feedstock for cellulosic bioenergy production because of the extensive area upon which the crop is already grown. This report summarizes 239 site-years of field research examining effects of zero, moderate, and high stover removal rates at 36 sites in seven different states. Grain and stover yields from all sites as well as N, P, and K removal from 28 sites are summarized for nine longitude and six latitude bands, two tillage practices (conventional vs no tillage), two stover-harvest methods (machine vs calculated), and two crop rotations {continuous corn (maize) vs corn/soybean [Glycine max (L.) Merr.]}. Mean grain yields ranged from 5.0 to 12.0 Mg ha−1 (80 to 192 bu ac−1). Harvesting an average of 3.9 or 7.2 Mg ha−1(1.7 or 3.2 tons ac−1) of the corn stover resulted in a slight increase in grain yield at 57 and 51 % of the sites, respectively. Average no-till grain yields were significantly lower than with conventional tillage when stover was not harvested, but not when it was collected. Plant samples collected between physiological maturity and combine harvest showed that compared to not harvesting stover, N, P, and K removal was increased by 24, 2.7, and 31 kg ha−1, respectively, with moderate (3.9 Mg ha−1) harvest and by 47, 5.5, and 62 kg ha−1, respectively, with high (7.2 Mg ha−1) removal. This data will be useful for verifying simulation models and available corn stover feedstock projections, but is too variable for planning site-specific stover harvest

Twelve Years of Stover Removal Increases Soil Erosion Potential without Impacting Yield

Corn (Zea mays L.) stover (non-grain aboveground biomass) in the US Corn Belt is used increasingly for livestock grazing and co-feed and for cellulosic bioenergy production. Continuous stover removal, however, could alter long-term agricultural productivity by affecting soil organic C (SOC) and soil physical properties, indicators of soil fertility and erosion potential. In this study, we showed that 12 consecutive yr of 55% stover removal did not affect mean grain yields at any N fertilizer rate (4.5, 6.3, and 6.0 Mg ha−1 for 60, 120, and 180 kg N ha−1 yr−1, respectively) in a marginally productive, rainfed continuous corn system under no-till (NT). Although SOC increased in the top 30 cm of all soils since 1998 (0.54–0.79 Mg C ha−1 yr−1), stover removal tended to limit SOC gains compared with no removal. Near-surface soils (0–5-cm depth) were more sensitive to stover removal and showed a 41% decrease in particulate organic matter stocks, smaller mean weight diameter of dry soil aggregates, and lower abundance of water-stable soil aggregates compared with soils with no stover removal. Increasing N fertilizer rate mitigated losses in total water-stable aggregates in near-surface soils related to stover removal. Collectively, however, our results indicated soil structure losses in surface soils due to lower C inputs. Despite no effect on crop yields and overall SOC gains with time using NT management, annually removing stover for 12 yr resulted in a higher risk of wind and water erosion at this NT continuous corn site in the western Corn Belt

USING AN ACTIVE OPTICAL SENSOR TO IMPROVE NITROGEN MANAGEMENT IN CORN PRODUCTION

Corn nitrogen (N) applications are still done on a field basis in Kentucky, according to previous crop, soil tillage management and soil drainage. Soil tests, as well as plant analysis for N, are not very useful in making N fertilizer rate recommendations for corn. Recommended rates assume that only 1/3 to 2/3 of applied N is recovered, variability largely due to the strong affect of weather on the release of soil N and fertilizer N fate. Many attempts have been made to apply N in a more precise and efficient way. Two experiments were conducted at Spindeltop, the University of Kentucky’s experimental farm near Lexington, over two years (2010, 2011), using a commercially available active optical sensor (GreanSeekerTM) to compute the normalized difference vegetative index (NDVI), and with this tool/index assess the possibility of early (V4-V6) N deficiency detection, grain yield prediction by NDVI with and without side-dressed N, and determination of the confounding effect of soil background on NDVI measurements. Results indicated that the imposed treatments affected grain yield, leaf N, grain N and grain N removal. Early N deficiency detection was possible with NDVI. The NDVI value tended to saturate in grain yield prediction models. The NDVI was affected by tillage management (residue/soil color background differences), which should be taken into account when using NDVI to predict grain yield. Side-dress N affected NDVI readings taken one week after side-dressing, reducing soil N variability and plant N nutrition. There is room for improvement in the use of this tool in corn N management

Effects of Corn (Zea mays L.) Stover Removal and Leaching on Soil Test and Whole Plant K Levels in Corn and K Fertilization/High-Input Treatments on Soybean Using Site-Specific Management to Increase Soybean (Glycine max) Production in South Dakota

Potassium is important for crop production. Corn stover removal has the potential to reduce exchangeable and soluble soil potassium (K+) needed for optimal plant growth in addition to grain yield. An experiment was conducted in Aurora, SD, USA, to observe the effects of corn stover removal on water soluble and exchangeable soil test K+ (STK) levels and corn grain yields across a five-year period. Abundant K+ reserves were recorded between the initial and final sampling periods. While corn grain yields were affected by removing corn biomass, exchangeable and solution K+ levels were relatively unaffected by stover removal. Potassium fertilizer has the potential to mitigate yield decreases associated with corn stover removal. An on-farm cooperation amongst producers who have had an extensive history of corn stover removal was initiated. Two K+ fertilization rates were spread per acre across half-mile strips in spring 2014; 250 lbs K2O and 0 lbs K2O. Initial (spring) and final (fall) soil sampling quantified STK values. Stomatal conductance and tissue sampling indicated K+ fertilization influences on crop physiology and K+ concentrations, respectively. Yield monitor data from treatment strips were cleaned and analyzed. Yield difference maps were generated through statistical software programs to examine yield responses to K+ fertilizer. While yield increases were not economically sufficient, a wide degree of site-specific variability existed between sampling periods and points, site locations, and season. Nitrogen (N) fertilization has the potential to increase soybean grain yield. Onfarm cooperators applied nitrogen fertilizer in the encapsulated urea nitrogen (ESN) form in two rates across half-mile strips at R1 growth stage in July 2014; 0 lbs N/acre and 75 lbs N/acre strips (replicated at least twice per field). Spatial variability in yield responses across soil topography and elevations was seen. While yield gains were statistically significant after applying ESN, economic analysis proved applications of ESN on soybean at R3 to be uneconomical in some localities while advantageous in others. Offsite K+ movement may occur following precipitation after corn physiological maturity, presumably through leaching off of corn biomass material. Whole corn plant portions were collected and tested for K+ following rainfall event. The portion of K+ leached relative to total plant K+ concentration indicated that corn stover biomass has great offsite movement, occurring as a function of rainfall inch rather than cumulative rainfall amounts