Integrated use of phosphorus fertilizer and farmyard manure improves wheat productivity by improving soil quality and P availability in calcareous soil under subhumid conditions.

Introduction: Low soil fertility and high fertilizer costs are constraints to wheat production, which may be resolved with integrating fertilizer phosphorus (P) and farm-yard manure (FYM). Study objectives were to evaluate P source impacts on soil, P efficiency, and wheat growth in a calcareous soil. Methods: Treatments included P fertilizer (0, 17, 26, or 39 kg P ha-1) and/or FYM (0 or 10 T ha-1) in a: 1) incubation experiment and 2) wheat (Triticum aestivum spp.) field experiment. Results and Discussion: Soil organic matter increased (30-72%) linearly for both fertilizer and FYM, whereas pH decreased (0.1-0.3 units) with fertilizer only. Addition of fertilizer and FYM increased plant available P (AB-DTPA extractable soil P) an average of 0.5 mg P kg-1 soil week-1 with incubation. The initial increase was 1-9 mg P kg-1, with further increase after 84 d of ~3-17 mg P kg-1. There was also a significant increase of available P in the soil supporting plants in the field study, although the magnitude of the increase was only 2 mg kg-1 at most for the highest fertilizer rate + FYM. Grain (66 to 119%) and straw (25-65%) yield increased significantly, peaking at 26 kg P ha-1 + FYM. The P Absorption Efficiency (PAE), P Balance (PB), and P Uptake (PU) increased linearly with P rate, with the highest levels at the highest P rate. The P Use Efficiency (PUE) was highest at the lowest rates of P, with general decreases with increasing P, although not consistently. Principal component analysis revealed that 94.34 % of the total variance was accounted for with PC1 (84.04 %) and PC2 (10.33 %), with grain straw yield significantly correlated to SOM, PU, and PAE. Regression analysis showed highly significant correlation of PB with P-input (R2= 0.99), plant available P (R2= 0.85), and PU (R2= 0.80). The combination of FYM at the rate of 10 T ha-1 and fertilizer P at 26 kg P ha-1 was found as the optimum dose that significantly increased yield. It is concluded that FYM concoction with fertilizer-P not only improved SOM and residual soil P, but also enhanced wheat yields with reasonable P efficiency.

Nitrogen release rates from slow- and controlled-release fertilizers influenced by placement and temperature.

Controlled-release and slow-release fertilizers can effectively supply nitrogen (N) while mitigating N loss. To determine the suitability of these fertilizers for plants in semi-arid environments, these fertilizers need to be evaluated under varying placement and temperature conditions. Several urea fertilizers were evaluated, including: uncoated, sulfur-coated (SCU), polymer-coated-sulfur-coated (PCSCU), and polymer-coated (PCU) with projected release timings between 45 and 180 d. Nitrogen release was measured under daily fluctuating or static temperatures applied either to the surface or buried in the soil. A second experiment consisted of two PCU sources and added a hanging bag placement comparison and low and high soil moisture treatments. For the first Experiment, the N in uncoated urea released shortly after application. The SCU and PCSCU treatments released > 80% of the N before the first sampling date. With fluctuating temperatures, the PCU 45, 75, 120, and 180 incorporated into the soil released N within +9, +9, -22, and -68 d of their expected timing. However, they released their N within 35 d when surface applied. Conversely, with static temperatures, PCU products released slowly, releasing under 80% for the entire study. The second experiment verified these results and showed no difference between low and high moisture and minimal release with fertilizer not in contact with soil. Each coated fertilizer in these studies exhibited slow/control release properties, but the PCU (surface applied) and SCU/PCSCU (surface applied or incorporated in soil) release was much more rapid than expected. Our research suggests that, although the SCU and PCSCU showed minimal slow-release properties (regardless of placement), the PCU fertilizers incorporated in the soil do have a controlled release approximate to what is expected, but have a much more rapid release when surface applied.

Phosphorus Management in High-Yield Systems.

The discovery and development of phosphorus (P) and P fertilizers provide context for current management conventions. Average crop yields were stagnant before the Green Revolution but have steadily increased since. This, along with conventional P management, has resulted in widely depleting soil P levels. Improved technology and management are needed to meet the increasing P demand. Modern hybrids and cultivars have different P demand and uptake patterns that require changes in conventional P fertilizer placement and timing. Phosphorus fertilizer recommendations based on soil analysis remains valid, but evidence suggests a need for recalibrating soil test P (STP) critical levels (the STP concentration at which a response to P fertilizer would not be expected) and P fertilizer rates to accommodate high-yield scenarios. Considering higher P fertilizer rates as a single solution poses environmental challenges, highlighting the need for improved P use efficiency (PUE). Phosphorus fertilization approaches that have the potential to improve PUE and enable high yields include crop-specific precision placement of P, informed timing of P fertilizers, and new enhanced efficiency sources of P fertilizer. This paper examines these management approaches from historical, production, and environmental perspectives in modern cropping systems.

Assessing atmospheric nitrogen losses with photoacoustic infrared spectroscopy: Polymer coated urea.

Although N is beneficial and essential for life, it is also a common atmospheric pollutant as nitrous oxide (N2O) and ammonia (NH3)-contributed largely from N fertilization. Polymer-coated urea (PCU) fertilizer is a promising controlled release fertilizer that provides improved N-release timing. Glasshouse studies were conducted to compare N2O and NH3 emissions from PCU and uncoated urea to an untreated control utilizing a non-static, non-flow-through chamber in conjunction with photoacoustic infrared spectroscopy (PAIRS) for gas collection and analysis. Three short-term 20-Day Studies with sand, sandy loam, and loam soils and a full-term 45-Day Study with loam soil were completed. Volatilization of NH3 was reduced by 72% and 22% in the sandy loam and loam soils, respectively, in two of the short-term studies and by 14% in the loam in the full-term study. Evolution of N2O was reduced by 42% and 63% in the sandy loam and loam soils of the short-term studies and by 99% in the loam soil of the full-term study. No differences were observed in the sand soil. Overall, PCU decreased gaseous losses of N following fertilization while providing a steady supply of N to the plant. Higher temporal resolution was observed with the PAIRS instrumentation as compared to what is typically reported and, as such, we recommend PAIRS analysis as a viable method for studying N gas emissions.

Multivariate soil fertility relationships for predicting the environmental persistence of 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-tricyclohexane (RDX) among taxonomically distinct soils.

After nearly a century of use in numerous munition platforms, TNT and RDX contamination has turned up largely in the environment due to ammunition manufacturing or as part of releases from low-order detonations during training activities. Although the basic knowledge governing the environmental fate of TNT and RDX are known, accurate predictions of TNT and RDX persistence in soil remain elusive, particularly given the universal heterogeneity of pedomorphic soil types. In this work, we proposed overcoming this problem by considering the environmental persistence of these munition constituents (MC) as multivariate mathematical functions over a variety of taxonomically distinct soil types, instead of a single constant or parameter of a specific absolute value. To test this idea, we conducted experiments where the disappearance kinetics of TNT and RDX were measured over a >300 h period in taxonomically distinct soils. Classical fertility-based soil measurements were log-transformed, statistically decomposed, and correlated to TNT and RDX disappearance rates (k-TNTand k-RDX) using multivariate dimension-reduction and correlation techniques. From these efforts, we generated multivariate linear functions for k parameters across different soil types based on a statistically reduced set of their chemical and physical properties: Calculations showed that the soil properties exhibited strong covariance, with a prominent latent structure emerging as the basis for relative comparisons of the samples in reduced space. Loadings describing TNT degradation were largely driven by properties associated with alkaline/calcareous soil characteristics, while the degradation of RDX was attributed to the soil organic matter content - reflective of an important soil fertility characteristic. In spite of the differing responses to the munitions, batch data suggested that the overall nutrient dynamics were consistent for each soil type, as well as readily distinguishable from the other soil types used in this study. Thus, we hypothesized that the latent structure arising from the strong covariance of full multivariate geochemical matrix describing taxonomically distinguished "soil types" may provide the means for potentially predicting complex phenomena in soils.

Multivariate functions for predicting the sorption of 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-tricyclohexane (RDX) among taxonomically distinct soils.

After nearly a century of use in numerous munition platforms, TNT and RDX contamination has turned up largely in the environment due to ammunition manufacturing or as part of releases from low-order detonations during training activities. Although the basic knowledge governing the environmental fate of TNT and RDX are known, accurate predictions of TNT and RDX persistence in soil remain elusive, particularly given the universal heterogeneity of pedomorphic soil types. In this work, we proposed a new solution for modeling the sorption and persistence of these munition constituents as multivariate mathematical functions correlating soil attribute data over a variety of taxonomically distinct soil types to contaminant behavior, instead of a single constant or parameter of a specific absolute value. To test this idea, we conducted experiments measuring the sorption of TNT and RDX on taxonomically different soil types that were extensively physical and chemically characterized. Statistical decomposition of the log-transformed, and auto-scaled soil characterization data using the dimension-reduction technique PCA (principal component analysis) revealed a strong latent structure based in the multiple pairwise correlations among the soil properties. TNT and RDX sorption partitioning coefficients (KD-TNT and KD-RDX) were regressed against this latent structure using partial least squares regression (PLSR), generating a 3-factor, multivariate linear functions. Here, PLSR models predicted KD-TNT and KD-RDX values based on attributes contributing to endogenous alkaline/calcareous and soil fertility criteria, respectively, exhibited among the different soil types: We hypothesized that the latent structure arising from the strong covariance of full multivariate geochemical matrix describing taxonomically distinguished soil types may provide the means for potentially predicting complex phenomena in soils. The development of predictive multivariate models tuned to a local soil's taxonomic designation would have direct benefit to military range managers seeking to anticipate the environmental risks of training activities on impact sites.

Polymer Coated Urea in Turfgrass Maintains Vigor and Mitigates Nitrogen's Environmental Impacts.

Polymer coated urea (PCU) is a N fertilizer which, when added to moist soil, uses temperature-controlled diffusion to regulate N release in matching plant demand and mitigate environmental losses. Uncoated urea and PCU were compared for their effects on gaseous (N2O and NH3) and aqueous (NO3(-)) N environmental losses in cool season turfgrass over the entire PCU N-release period. Field studies were conducted on established turfgrass sites with mixtures of Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.) in sand and loam soils. Each study compared 0 kg N ha(-1) (control) to 200 kg N ha(-1) applied as either urea or PCU (Duration 45CR®). Application of urea resulted in 127-476% more evolution of measured N2O into the atmosphere, whereas PCU was similar to background emission levels from the control. Compared to urea, PCU reduced NH3 emissions by 41-49% and N2O emissions by 45-73%, while improving growth and verdure compared to the control. Differences in leachate NO3(-) among urea, PCU and control were inconclusive. This improvement in N management to ameliorate atmospheric losses of N using PCU will contribute to conserving natural resources and mitigating environmental impacts of N fertilization in turfgrass.