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

Effects of straw returning combined with blended controlled-release urea fertilizer on crop yields, greenhouse gas emissions, and net ecosystem economic benefits: A nine-year field trial

Although straw returning combined with blended controlled-release urea fertilizer (BUFS) has been shown to improve wheat-maize rotation system productivity, their effects on greenhouse gas (GHG) emissions, carbon footprints (CF), and net ecosystem economic benefits (NEEB) are still unknown. Life cycle assessment was used to investigate a long-term (2013-2022) wheat-maize rotation experiment that included straw combined with two N fertilizer types [BUFS and (conventional urea fertilizer) CUFS] and straw-free treatments (BUF and CUF). The results showed that BUFS and CUFS treatments increased the annual yield by 13.8% and 11.5%, respectively, compared to BUF and CUF treatments. The BUFS treatment increased the yearly yield by 13.8% compared to the CUFS treatment. Since BUFS and CUFS treatments increased soil organic carbon (SOC) sink sequestration by 25.0% and 27.0% compared to BUF and CUF treatments, they reduced annual GHG emissions by 7.1% and 4.7% and CF per unit of yield (CFY) by 13.7% and 9.6%, respectively. BUFS treatment also increased SOC sink sequestration by 20.3%, reduced GHG emissions by 10.7% and CFY by 23.0% compared to CUFS treatment. It is worth noting that the BUFS and CUFS treatments increased the annual ecological costs by 41.6%, 26.9%, and health costs by 70.1% and 46.7% compared to the BUF and CUF treatments, but also increased the net yield benefits by 9.8%, 6.8%, and the soil nutrient cycling values by 29.2%, 27.3%, and finally improved the NEEB by 10.1%, 7.3%, respectively. Similar results were obtained for the BUFS treatment compared to the CUFS treatment, ultimately improving the NEEB by 23.1%. Based on assessing yield, GHG emissions, CF, and NEEB indicators, the BUFS treatment is recommended as an ideal agricultural fertilization model to promote sustainable and clean production in the wheat-maize rotation system and to protect the agroecological environment.

Effect of a Prolonged-Release System of Urea on Nitrogen Losses and Microbial Population Changes in Two Types of Agricultural Soil

Urea is the nitrogen-containing fertilizer most used in agricultural fields; however, the nutrient given by the urea is lost into the environment. The aim of this research was to determine the effect of two soil textures by applying a prolonged-release system of urea (PRSU) on the N losses. This research shows an important decrease of the nitrate and ammonium losses from 24.91 to 87.94%. Also, the microbiological population increases after the application of the PRSU. It was concluded that both soil textures presented the same loss-reduction pattern, where the N from the nitrates and ammonium was reduced in the leachates, increasing the quality of the soil and the microbial population in both soil textures after the PRSU application.

Urbanization can accelerate climate change by increasing soil N2 O emission while reducing CH4 uptake

Urban land-use change has the potential to affect local to global biogeochemical carbon (C) and nitrogen (N) cycles and associated greenhouse gas (GHG) fluxes. We conducted a meta-analysis to (1) assess the effects of urbanization-induced land-use conversion on soil nitrous oxide (N₂ O) and methane (CH₄ ) fluxes, (2) quantify direct N₂ O emission factors (EF_d ) of fertilized urban soils used, for example, as lawns or forests, and (3) identify the key drivers leading to flux changes associated with urbanization. On average, urbanization increases soil N₂ O emissions by 153%, to 3.0 kg N ha^-1  year^-1 , while rates of soil CH₄ uptake are reduced by 50%, to 2.0 kg C ha^-1  year^-1 . The global mean annual N₂ O EF_d of fertilized lawns and urban forests is 1.4%, suggesting that urban soils can be regional hotspots of N₂ O emissions. On a global basis, conversion of land to urban greenspaces has increased soil N₂ O emission by 0.46 Tg N₂ O-N year^-1 and decreased soil CH₄ uptake by 0.58 Tg CH₄ -C year^-1 . Urbanization driven changes in soil N₂ O emission and CH₄ uptake are associated with changes in soil properties (bulk density, pH, total N content, and C/N ratio), increased temperature, and management practices, especially fertilizer use. Overall, our meta-analysis shows that urbanization increases soil N₂ O emissions and reduces the role of soils as a sink for atmospheric CH₄ . These effects can be mitigated by avoiding soil compaction, reducing fertilization of lawns, and by restoring native ecosystems in urban landscapes.

Field evaluation of slow-release nitrogen fertilizers and real-time nitrogen management tools to improve grain yield and nitrogen use efficiency of spring maize in Nepal

Several innovative fertilizers and application methods, along with different decision support tools have been developed to improve nitrogen use efficiency (NUE) and crop yields, but their comparative study in maize is yet to be done in Nepal. Thus, we evaluated different slow-release N fertilizers and decision-making tools for real-time N management compared with the common urea on their effectiveness in increasing NUE, grain yield and economic return of spring maize (Zea mays L. cv. Rampur Hybrid-10). A field trial was conducted at Dang Valley of Nepal in a Randomized complete block design with three replications and seven treatments; N omission- (0 kg N ha⁻¹), normal urea at 120 kg N ha⁻¹ (recommended dose, N120), and 180 kg N ha⁻¹(N180), Polymer Coated Urea (PCU- 90 kg N ha⁻¹), Urea Briquette-deep placement (UDP- 90 kg N ha⁻¹), GreenSeeker (GS- 143 kg N ha⁻¹) and Leaf Color Chart based N management (LCC- 143 kg N ha⁻¹). N application based on decision support tools (LCC and GS) and innovative fertilizers (UDP, PCU) yielded 17.35–45.81% more grain yield than recommended dose (RDF). The real time nitrogen application through LCC and GreenSeeker and slow release N fertilizer (PCU and UDP) resulted in higher agronomic efficiency of nitrogen- AEN (21.30–27.82 kg grain kg⁻¹ N) compared to RDF (12.15 kg grain kg⁻¹ N) and N180 (19.87 kg grain kg⁻¹ N). UDP, with 25% less N compared to RDF, resulted in higher grain yield (5.25 t ha⁻¹), partial factor productivity of N– PFPN (58.37 kg grain kg⁻¹ N) and AEN (27.82 kg grain kg⁻¹ N). Based on the economic return and ease in the application, both UDP and LCC based N application seem promising in Nepalese conditions. However, their effectiveness should be validated across diverse agro-ecologies, soil types and climatic conditions for a general recommendation.

Temporal Recovery of Polymer-Coated Urea-N by Kentucky Bluegrass in the Field

Relative to soluble N sources, controlled release fertilizer (CRF) fosters consistent turfgrass growth response and improved canopy quality while reducing N loss as nitrate, ammonia, and/or N2O from target systems. Commercial CRFs afford turfgrass managers greater operational efficiency and flexibility in nutrient management planning and compel the investigation of application rate thresholds to guide regional agencies tasked with their regulation. The experimental objective was to systematically evaluate, under an array of field conditions, Kentucky bluegrass (Poa pratensis L.) vigor/yield, fertilizer N offtake, canopy density, and canopy color temporal response to a single application of granular N fertilizer made at practical rates. In May of 2014 and 2015, plots within a mature Kentucky bluegrass system were fertilized by conventional urea or Duration 45 polymer coated urea (PCU) at a N rate of 43.9 kg·ha−1 (0.9 lbs N·1000 ft−2); or PCU (Duration 90, Duration 120, or 43% N Polyon) at a N rate of 87.8 kg·ha−1 (1.8 lbs N·1000 ft−2). Resulting measures of the described dependent variables proved similar over both growing seasons and were highly dependent on the N rate and PCU attribute. Following 18-week evaluations, the average total percent fertilizer N recoveries from conventional urea, Duration 45, Duration 90, Duration 120, and Polyon (43% N) were 63%, 87%, 82%, 78%, and 77%, respectively. Temporal release among commercial PCU fertilizers indicates varying suitability by commodity and seasonal nutrient requirements. Hypothesis tests on experiment-end unaccounted fertilizer N totals show one 87.8 kg N·ha−1 application of the described 100% PCU fertilizer treatments poses no greater environmental risk than a 43.9 kg N·ha−1 application of conventional urea fertilizer.

Reducing nitrate leaching losses from turfgrass fertilization of residential lawns

Fertilizer applications on lawns have raised environmental concerns in many Canadian municipalities. In this greenhouse study, NO₃ -N leaching losses from Kentucky bluegrass (Poa pratensis L.) lawns were evaluated on two soils (a schist loam and a clay loam) and on a sand/peat moss rootzone mix (80% sand, 20% peat moss). Eight different fertilizer N sources (urea, Polyon 8 and 12-wk release, Duration 45 and 90-d release, XCU, corn gluten meal, and UFLEXX) were assessed at five application rates (25-200 kg N ha^-1  yr^-1 ) and two application frequencies over two 8-wk trials. Average NO₃ -N concentration in leachate were measured at levels of 3.5, 7.4, and 1.4 mg L^-1 from turf grown in loam, clay, and sand respectively, but losses from loam and clay were mostly affected by N mineralization from organic matter. Turf fertilized with rates ≥100 kg N ha^-1 generally resulted in acceptable visual quality on both soils, but coated-urea fertilizers were more efficient to reduce leaching. In sand, UFLEXX and urea (150 and 200 kg N ha^-1 ) as well as XCU (200 kg N ha^-1 ) resulted in higher NO₃ -N losses, varying from 8.5 to 23.7 mg L^-1 , and losses from other N sources were consistently below 3 mg L^-1 . Our results show that it is possible to maintain good quality turfgrass while keeping low NO₃ -N leaching losses (i.e., <4 mg L^-1 ) in loam, clay, and sand by selecting the ideal combination of N source, N rate, and application frequency.

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.

Soil greenhouse gas emissions from Australian sports fields

Managed turf is a potential net source of greenhouse gas (GHG) emissions. While most studies to date have focused on non-sports turf, sports turf may pose an even greater risk of high GHG emissions due to the generally more intensive fertiliser, irrigation and mowing regimes. This study used manual and automated chambers to measure nitrous oxide (N₂O) and methane (CH₄) emissions from three sports fields and an area of non-sports turf in southern Australia. Over 213 days (autumn to late spring), the average daily N₂O emission was 37.6 g N ha^-1day^-1 at a sports field monitored at least weekly and cumulative N₂O emission was 2.5 times higher than the adjacent non-sports turf. Less frequent seasonal sampling at two other sports fields showed average N₂O daily emission ranging from 26 to 90 g N ha^-1 day^-1. Management practices associated with periods of relatively high N₂O emissions were surface renovation and herbicide application. CH₄ emissions at all of the sports fields were generally negligible with the exception of brief periods when soil was waterlogged following heavy rainfall where emissions of up to 1.3 kg C ha^-1 day^-1 were recorded. Controlled release and nitrification inhibitor containing fertilisers didn't reduce N₂O, CH₄ or CO₂ emissions relative to urea in a short term experiment. The N₂O emissions from the sports fields, and even the lower emissions from the non-sports turf, were relatively high compared to other land uses in Australia highlighting the importance of accounting for these emissions at a national level and investigating mitigation practices.

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.

Effect of Trichoderma viride biofertilizer on ammonia volatilization from an alkaline soil in Northern China

Ammonia (NH₃) volatilization is one of the primary pathways of nitrogen (N) loss from soils after chemical fertilizer is applied, especially from the alkaline soils in Northern China, which results in lower efficiency for chemical fertilizers. Therefore, we conducted an incubation experiment using an alkaline soil from Tianjin (pH8.37-8.43) to evaluate the suppression effect of Trichoderma viride (T. viride) biofertilizer on NH₃ volatilization, and compared the differences in microbial community structure among all samples. The results showed that viable T. viride biofertilizer (T) decreased NH₃ volatilization by 42.21% compared with conventional fertilizer ((CK), urea), while nonviable T. viride biofertilizer (TS) decreased NH₃ volatilization by 32.42%. NH₃ volatilization was significantly higher in CK and sweet potato starch wastewater (SPSW) treatments during the peak period. T. viride biofertilizer also improved the transfer of ammonium from soil to sweet sorghum. Plant dry weights increased 91.23% and 61.08% for T and TS, respectively, compared to CK. Moreover, T. viride biofertilizer enhanced nitrification by increasing the abundance of ammonium-oxidizing archaea (AOA) and ammonium-oxidizing bacteria (AOB). The results of high-throughput sequencing indicated that the microbial community structure and composition were significantly changed by the application of T. viride biofertilizer. This study demonstrated the immense potential of T. viride biofertilizer in reducing NH₃ volatilization from alkaline soil and simultaneously improving the utilization of fertilizer N by sweet sorghum.

Quantitative study on the fate of residual soil nitrate in winter wheat based on a 15N-labeling method

A considerable amount of surplus nitrogen (N), which primarily takes the form of nitrate, accumulates in the soil profile after harvesting crops from an intensive production system in the North China Plain. The residual soil nitrate (RSN) is a key factor that is included in the N recommendation algorithm. Quantifying the utilization and losses of RSN is a fundamental necessity for optimizing crop N management, improving N use efficiency, and reducing the impact derived from farmland N losses on the environment. In this study, a ¹⁵N-labeling method was introduced to study the fate of the RSN quantitatively during the winter wheat growing season by ¹⁵N tracer technique combined with a soil column study. A soil column with a 2 m height was vertically divided into 10 20-cm layers, and the RSN in each layer was individually labeled with a ¹⁵N tracer before the wheat was sown. The results indicated that approximately 17.68% of the crop N derived from RSN was located in the 0–2 m soil profile prior to wheat sowing. The wheat recovery proportions of RSN at various layers ranged from 0.21% to 33.46%. The percentages that still remained in the soil profile after the wheat harvest ranged from 47.08% to 75.44%, and 19.46–32.64% of the RSN was unaccounted for. Upward and downward movements in the RSN were observed, and the maximum upward and downward distances were 40 cm and 100 cm, respectively. In general, the ¹⁵N-labeling method contributes to a deeper understanding of the fates of the RSN. Considering the low crop recovery of the RSN from deep soil layers, water and N saving practices should be adopted during crop production.