Broadcast Urea Research Articles

Soil greenhouse gas emissions under enhanced efficiency and urea nitrogen fertilizer from Australian irrigated aerobic rice production

AbstractAerobic rice production offers a promising solution to improve water use efficiency and reduce methane (CH4) emissions by minimizing water inundation. However, alternate water‐saving methods for rice cultivation can lead to “trade‐off” emissions of nitrous oxide (N2O). A field experiment was conducted over one season measuring soil‐derived greenhouse gas emissions in irrigated aerobic rice (Oryza sativa L.) under different N fertilizer management at a rate of 220 kg N ha−1, including a nil treatment (“control”); slow release (180 days) polymer‐coated urea (“N180”); banded urea applied upfront (“urea”); and three applications of broadcast urea (“urea‐split”). The N180 treatment reduced soil N2O emissions compared with urea (p < 0.001), with mean cumulative N2O emissions of 4.36 ± 1.07 kg N ha−1 and 27.9 ± 5.70 kg N ha−1, respectively. Soil N2O fluxes were high, reaching up to 1916 and 2900 µg N m2 h−1 after urea application and irrigation/rain events, and were similar to other irrigated crops grown on heavy textured soils. Fertilizer N management had no effect on soil CH4 emissions, which were negligible across all treatments ranging from 1.28 to 2.75 kg C ha−1 over the growing season. Cumulative soil carbon dioxide emissions ranged from 1936 to 3071 kg C ha−1 and were greatest in N180. This case study provides the first evidence in Australia that enhanced efficiency nitrogen fertilizer can substantially reduce N2O emissions from soils in an aerobic rice system. Our findings reinforce the CH4 mitigation potential of water saving rice approaches and demonstrate the need to consider N fertilizer management to control N2O emissions.

Nitrogen source regulates soil nitrification and nitrogen losses more than nitrification inhibitor and herbicide: A laboratory evaluation

AbstractIncreased environmental nitrogen (N) losses have prompted the use of enhanced efficiency nitrogen fertilizers, including nitrification inhibitors. However, the comparative effects of nitrification inhibitors with conventional nitrogen fertilizers and herbicides on soil nitrification and nitrogen losses remain poorly understood. This study evaluated the impact of a nitrification inhibitor (Instinct NXTGEN), two nitrogen sources (broadcast urea vs. injected aqueous ammonia), and a preemergence herbicide (Acuron) on (1) soil nitrification through a 25‐day soil incubation experiment and (2) NH3 volatilization, NO3‐N leaching, and N2O‐N emissions through a 31‐day soil column study in loamy sand soil. In both experiments, treatments included combinations of nitrification inhibitor versus no inhibitor, two nitrogen sources, and preemergence herbicide versus no herbicide. Results revealed that nitrogen source significantly influenced nitrification, with injected aqueous ammonia reducing nitrification by 33% compared to surface broadcast urea. Nitrification inhibitors and herbicide had no effect on soil nitrification. Injected aqueous ammonia reduced NH3 volatilization by 87% compared to surface broadcast urea, but the effect of the nitrification inhibitor on NH3 volatilization was inconsistent across both nitrogen sources. Injected aqueous ammonia led to 39% higher cumulative nitrogen (NO3‐N + NH4‐N) leaching than urea, while the nitrification inhibitor had an inconsistent effect on NO3‐N leaching across both nitrogen sources. No significant differences in N2O‐N emissions were observed among treatments, and the herbicide had no effect on any measured parameters. These findings suggest that nitrogen source plays a more critical role in regulating soil nitrogen losses than nitrification inhibitors or herbicides.

Efficacy of fertilizer nitrogen source, stabilizer, and application timing for corn nitrogen nutrition

AbstractEnhancing fertilizer nitrogen use efficiency (NUE) in corn (Zea mays L.) production is critical for closing yield gaps, increasing producer profitability, and promoting environmental stewardship. In 2014 and 2015, a field experiment was conducted to determine the potential for fertilizer N stabilizer products to improve NUE of granular urea and urea ammonium nitrate (UAN) solution applied to strip‐till corn. A urease inhibitor (UI) or nitrification inhibitor (NI) or both were added at labeled rates to urea or UAN solution for a target rate of 180 kg N ha−1. At V3, a single application of broadcast granular urea and subsurface banded UAN solution with and without fertilizer N stabilizers was made. A split application (50% at V3; 50% at V6) of subsurface banded UAN solution served as a control representing a standard grower practice. Fertilizer N stabilizers improved components of NUE, such as grain N recovery efficiency (GNRE) and partial factor productivity (PFP). A single full rate UAN application did not differ in terms of grain yield each year but did result in less PFP and GNRE in 2015 as compared to the grower standard practice. A timely one‐time full season N rate subsurface banded application of UAN treated with UI and NI to improve NUE could be a viable substitute for the practice of multiple fertilizations. Untreated broadcast urea was inferior to UAN as a N source for corn, but when treated with both a UI and NI, NUE was improved.

Stacking nitrogen management practices: Combining double‐slot fertilizer injection with urease and nitrification inhibitors improves yields and reduces ammonia and nitrous oxide emissions

AbstractAmmonia loss following nitrogen fertilization can degrade air quality and impact human health, whereas nitrous oxide (N2O) can contribute to global warming and climate change. Mitigation practices that target only one N‐loss pathway can lead to pollution swamping; hence, practices targeting both N‐losses are required. A 3‐year field study examined fertilizer N‐placement (broadcast urea, single‐slot injection of urea ammonium nitrate [UAN], double‐slot UAN injection) and N‐metabolization inhibitors (with/without urease and nitrification inhibitors) impacts on NH3 and N2O losses and corn yields. Ammonia volatilization was reduced (p < 0.05) by 26% with single‐slot UAN injection (10.6 kg N ha−1) and by 63% with double‐slot UAN injection (5.32 kg N ha−1) compared to broadcast urea (14.3 kg N ha−1). Dual urease and nitrification inhibitors reduced NH3 volatilization (0.84–3.86 kg N ha−1) by 57%–92% compared to no inhibitors (5.32–14.3 kg N ha−1). When no inhibitors were applied, N2O emissions from slot injection (6.43–7.62 kg N ha−1) were 2.6–3.1 times greater than from broadcast urea (2.43 kg N ha−1). Dual inhibitors reduced N2O emissions by 43% from 6.43 to 3.66 kg N ha−1 with double‐slot injection. Double‐slot UAN injection increased corn grain yields (9.73 t ha−1) by 12%–13% compared to single‐slot UAN injection (8.71 t ha−1) and broadcast urea (8.6 t ha−1). Double‐slot UAN injection effectively decreased NH3 losses and increased corn grain yields, but dual N inhibitors were required to also reduce N2O. Hence, combined productivity and environmental benefits were accrued only when fertilizer containing urease and nitrification inhibitors was combined with double‐slot injection.

Fertilizer Management Strategies of Glycine max L. (Soybean) in Northcentral and North-Western North Dakota

Soybean (Glycine max L.) is a new cash crop grown in north central and northwestern North Dakota (ND). Soils and climate in these new soybean areas differ from current fertilizer guidelines. A three-year study to evaluate soybean fertility best management practices was initiated in the spring of 2016 and concluded in 2018. Each year had two sites and twelve treatments. One site was acidic (pH < 6.2) and the other was alkaline (pH > 7.2). Both site treatments were: untreated check, inoculated with rhizobia (Bradyrhizobium japonicum L.), broadcast urea (55 kg ha−1), broadcast MAP (110 kg ha−1), In-furrow 10-34-0 (28 L ha−1), in-furrow 6-24-6 (28 L ha−1), foliar 3-18-18 (28 L ha−1) at V5 and R2, and foliar 3-18-18 (28 L ha−1) with sulfate (1.1 kg ha−1) at V5 and R2. The acidic site had two treatments of sugar beet (Beta vulgaris L.) waste lime (4411 kg ha−1 and 8821 kg ha−1). The alkaline site received treatments of iron ortho-ortho-EDDHA (7.1 L ha−1), and naked ortho-ortho-EDDHA (7.1 L ha−1). An in-furrow treatment of cobalt (2.9 kg cobalt-sulfate ha−1) was added in 2018. Fertilizer treatments did not impact soybean yield, protein content and oil content at the 0.05 significance level.

Efficacy of Mechanical Seedling Transplanter and Deep Placement of Mixed Fertilizer on Rice Yield

A field experiment was conducted at the West Byde of BRRI farm, Gazipur during T. Aman and Boro, 2021-22 season to evaluate the efficacy of newly developed mechanical rice transplanter cum fertilizer applicator. Five treatments in Randomized Complete Block Design with three replications. Field experiments was conducted on silty clay loam soil in Gazipur. Individual plot size was 8m×5m with 30 cm buffer zone. The treatments were T1 = Mechanical transplanting along with 100% fertilizer (Urea, TSP, MoP and Gypsum) deep placement, T2 = Mechanical transplanting along with 80% fertilizer (80% Urea and 100% TSP, MoP and Gypsum) deep placement, T3 = Mechanical transplanting along with 70% fertilizer (70% urea and 100% TSP, MoP and Gypsum) deep placement, T4 = Mechanical transplanting along with 100% fertilizer hand broadcasting (TSP, MoP and Gypsum fertilizer as basal dose and urea fertilizer in three split) and T5 = Hand transplanting of same seedling of rice transplanter along with 100% fertilizer hand broadcasting (TSP, MoP and Gypsum in basal dose and urea fertilizer in three split) and T6 = BRRI recommended practice. In this experiment, BRRI dhan89 and BRRI dhan92 was used in T. Aman and Boro seasons, respectively. In the field, saving percentage of urea fertilizer varied from 25% to 28% against the calibration of 30% of urea saving due to the variation of the machine, operational speed and more penetration of the driving wheel during operation. It was found that grain yield was varied with the mode and rate of urea fertilizer application. Mechanical transplanting along with urea fertilizer deep placement (80% of recommended dose) gave significantly higher yield compared to manual transplanting and hand broadcasting of urea. Mechanical transplanting along with deep placement of urea fertilizer is a promising technology for rice farmers in Bangladesh. Manual transplanting is tedious and time consuming as a result mechanical transplanting is seen as a solution of labor problems. No significant differences among the treatments was found in growth parameters. Significant variations were recorded in case of yield. BRRI recommended practice and mechanical transplanting with 80% urea with other fertilizers were produced very similar grain yield. From these results, it might be said that mechanical transplanting with 80% urea fertilizer is recommended with BRRI recommended hand transplanting practice. Urea saving is additional benefit with time savings and low transplanting cost when transplanted with rice transplanter cum fertilizer applicator.

Modelling the impacts of inhibitors and fertilizer placement on maize yield and ammonia, nitrous oxide and nitrate leaching losses in southwestern Ontario, Canada

Application of urease and nitrification inhibitors is an effective strategy for decreasing nitrogen (N) losses without negatively impacting yields, but the long-term impacts of inhibitors and N placement on N dynamics remains unclear. The objectives of this study were to 1) use a 3-year maize experiment in southwestern Ontario to evaluate the Denitrification-DeComposition (DNDC) model fitted with default and enhanced urea hydrolysis mechanisms, 2) determine the impacts of climate variability (30-year) on inhibitor performance on maize yield and N losses under a range of N treatments, and 3) estimate the optimal N application rates for maintaining high yield and minimizing N losses. The experiment treatments included a factorial arrangement of two N sources (urea, urea ammonium nitrate [UAN]), three N placement methods (broadcast urea [B-Urea], broadcast incorporated urea [BInc-Urea], injected UAN [Inj-UAN]), and three inhibitors (no inhibitor, urease inhibitor [UI], urease plus nitrification inhibitor [UI&NI]). Although both the default and improved model provided “fair” to “good” simulations of maize yield, N uptake, soil temperature, soil moisture, soil inorganic N content and nitrous oxide (N2O) emissions across treatments, more accurate simulations were obtained using the improved model. The default DNDC model indicated “poor” simulations of ammonia (NH3) volatilization according to the Nash-Sutcliffe efficiency (NSE <0) and index of agreement (d ≤ 0.38), whereas the improved DNDC produced “good” simulations (NSE = 0.22–0.39, d = 0.65–0.84) because of improved estimates of urea diffusion, hydrolysis and inhibitor efficiency. The 30-year simulation based upon 95% of the maximum yield resulted in annual NH3 losses of 35.4 kg N ha−1 for B-Urea and these losses were reduced by 40.1% with BInc-Urea and by 92.7% with Inj-UAN. When UI was added to either B-Urea or BInc-Urea, NH3 losses were reduced by 61.8–66.4%, whereas when UI&NI was added, losses were reduced by 41.0–49.4%. The Inj-UAN reduced annual N2O losses by 18.8% compared to B-Urea whereas two inhibitor treatments of B-Urea + UI&NI and BInc-Urea + UI&NI reduced N2O losses by 11.5–11.8% compared to B-Urea and BInc-Urea. Simulated annual N losses from Inj-UAN + UI&NI were reduced relative to Inj-UAN + UI because of decreased NO3− leaching. Simulated long-term average percentage of annual total N losses at the optimal N rate were 36.8, 30.8 and 22.0% from B-Urea, BInc-Urea and Inj-UAN, respectively, which reduced to 25.9–28.1, 24.9–25.5 and 21.2–21.9%, when inhibitors were added. Our study suggests that the DNDC model can be used to investigate the impacts of climate variability on inhibitor performance and determine the optimum range of N application rates for different inhibitor treatments.

Dressed for success. Are crop N uptake, N loss and lint yield of irrigated cotton affected by how in-crop N fertiliser is applied?

Soil mineral nitrogen (N) and mineralisable N need to be supplemented by N fertiliser to optimise the growth and lint yield of modern irrigated cotton varieties. Splitting N fertiliser application between pre- and post-sowing is common, but what is the most efficient means of in-crop N addition? Two field experiments were conducted over two seasons to investigate the effects of (1) in-crop urea application method and (2) water-run (fertigation) N product choice. In one year, sidedressed urea increased cotton growth and N uptake by up to 26% compared with broadcast urea or water-run urea, but did not increase lint yields. In the other year, sidedressing increased plant nodes and bolls, but not lint yield. Sidedressing also minimised the N lost in irrigation runoff or left behind as residual soil mineral N. The addition of a urease inhibitor to broadcast urea did not benefit crop production or reduce N loss. Irrigating 1–2 days after broadcasting obviates the need to inhibit urea hydrolysis. Water-run N application led to substantial N loss in irrigation runoff. The form of N lost (urea, ammonium, nitrate) differed between the products applied but total runoff losses were similar between urea, urea ammonium nitrate and ammonia. Additional N loss via ammonia volatilisation from the water-run ammonia treatment makes this product choice the least efficient. Further research to reduce N in irrigation runoff is warranted, especially when fertigation is used. The lack of cotton lint yield responses points to the minor contribution of fertilizer N to the plant’s needs in these years, and the need to account for the significant contribution of soil mineral N to plant uptake when devising fertilizer rates. Sidedressing with urea was the most N efficient means of in-crop N delivery. • In-crop urea application method did not affect cotton lint yields. • In-crop sidedressed urea increased N uptake and growth, reduced N loss. • Urease inhibitor with topdressed urea had no impact on lint yield or N runoff loss. • N loss via irrigation runoff was high for water-run urea. • Runoff losses and lint yields were similar for water-run UAN, ammonia and urea.

Recovery of nitrogen fertilizer can be doubled by urea-briquette deep placement in rice paddies

Nitrogen (N) recoveries in rice paddies have barely exceeded 60%, despite the implementation of several management strategies, amounting to significant N being lost to the environment. We conducted field experiments for three consecutive rice growing seasons at two locations in Myanmar to investigate the performance of urea-briquette deep placement (UDP) against variable rates of surface broadcast urea for improving N recovery and yields in rice paddies. The experiment consisted of a control (N0), 77.6 kg N ha−1 as UDP, and surface broadcast urea at 77.6 kg N ha−1 (N78), 100 kg N ha−1 (N100) and 160 kg N ha−1 (N160). Surface broadcast urea was applied in two equal splits at 10 days after transplanting (10 DAT) and at panicle initiation (PI) stage. Urea briquettes (2.7 g) were deep placed (75 mm) in the middle of four rice hills between alternate rows as a single dose at 10 DAT. Microplots receiving 15N labeled urea were installed in each treatment plot (except N100) to trace the fate of the applied N. Nitrogen input almost always produced higher grain yields (p < 0.05) compared to the control. Rice grain yield in the UDP treatment was similar or higher than in the N78, N100 and N160 treatments. Crop dry biomass yield in the UDP treatment was mostly higher (p < 0.05) than in the N78 and always similar to the N160 treatment. Higher crop (47–61%) and soil (24–40%) recovery of 15N was observed in the UDP treatment than in the N78 and N160 treatments, leading to total recoveries of 77–95%. The N78 treatment had crop recoveries of 30–37% and total recoveries of 41–60% and the N160 treatment had crop recoveries of 29–39% and total recoveries of 40–54%. The rice plants in the UDP treatment relied less on native soil N, indicating that the UDP practice can minimize soil N depletion. Our results show that UDP has substantial advantages over surface broadcasting in terms of N fertilizer recovery and may provide environmental benefits.

Using nitrification inhibitors and deep placement to tackle the trade-offs between NH3 and N2 O emissions in global croplands.

Ammonia (NH3 ) and nitrous oxide (N2 O) are two important air pollutants that have major impacts on climate change and biodiversity losses. Agriculture represents their largest source and effective mitigation measures of individual gases have been well studied. However, the interactions and trade-offs between NH3 and N2 O emissions remain uncertain. Here, we report the results of a two-year field experiment in a wheat-maize rotation in the North China Plain (NCP), a global hotspot of reactive N emissions. Our analysis is supported by a literature synthesis of global croplands, to understand the interactions between NH3 and N2 O emissions and to develop the most effective approaches to jointly mitigate NH3 and N2 O emissions. Field results indicated that deep placement of urea with nitrification inhibitors (NIs) reduced both emissions of NH3 by 67% to 90% and N2 O by 73% to 100%, respectively, in comparison with surface broadcast urea which is the common farmers' practice. But, deep placement of urea, surface broadcast urea with NIs, and application of urea with urease inhibitors probably led to trade-offs between the two gases, with a mitigation potential of -201% to 101% for NH3 and -112% to 89% for N2 O. The literature synthesis showed that deep placement of urea with NIs had an emission factor of 1.53%-4.02% for NH3 and 0.22%-0.36% for N2 O, which were much lower than other fertilization regimes and the default values recommended by IPCC guidelines. This would translate to a reduction of 3.86-5.47TgNyr-1 of NH3 and 0.41-0.50TgNyr-1 of N2 O emissions, respectively, when adopting deep placement of urea with NIs (relative to current practice) in global croplands. We conclude that the combination of NIs and deep placement of urea can successfully tackle the trade-offs between NH3 and N2 O emissions, therefore avoiding N pollution swapping in global croplands.

Injected Anhydrous Ammonia Is More Effective Than Broadcast Urea as a Source of Nitrogen for Drill Seeded Rice

Anhydrous ammonia is a cheaper source of nitrogen (N) fertiliser than granular urea for rice production, but it is not widely used in developing countries. It can only be applied pre-crop with any in-crop applications being applied in the form of urea. This 2-year study conducted in the Nile delta region of Egypt compared pre-crop anhydrous ammonia injected to a depth of 20 cm with broadcast urea as N sources for rice, along with 4 combinations of pre-crop ammonia and in-crop urea. Each treatment supplied a total of 165 kg N/ha. The rice crop was direct seeded rather than transplanted. The highest yields were achieved in the full anhydrous ammonia treatment, which yielded 53% more grain than the nil-N control, while the full urea treatment yielded 22% more than the control; most combination treatments were intermediate. The higher grain yield of the anhydrous ammonia treatment was through a higher panicle density per unit area and more filled grains per panicle. An economic analysis found that the anhydrous ammonia treatment had a net return 70–94% higher than supplying the same quantity of N as urea. Counts of bacteria, fungi and actinomycetes showed a decline by day 2 after injection of anhydrous ammonia, followed by an increase to numbers similar to or above pre-injection levels by day 5. The findings indicated that pre-crop anhydrous ammonia in rice is both economically promising and not deleterious to soil microbes.

Win-win for monosodium glutamate industry and paddy agriculture: Replacing chemical nitrogen with liquid organic fertilizer from wastewater mitigates reactive nitrogen losses while sustaining yields

Recycling nutrients from the monosodium glutamate (MSG) wastewater as a low-cost fertilizer is a cleaner practice in the MSG industry. However, the potential of liquid organic fertilizer (LOF) recovered from MSG wastewater serving as a substitute for chemical fertilizer, improving crop yields, and mitigating reactive nitrogen emissions, has not been investigated. In a two-year paddy field experiment, the LOF recovered from the MSG wastewater was used as top dressing, following a multi-splits fertigation way, to evaluate its effects on rice yield, nitrogen use efficiency (NUE), NH3 volatilization and nitrogen leaching losses. For top-dressed N, with local traditional top-dressing strategy (broadcast urea in three splits) as control (CF), LOF fertigated in seven splits (LOF160, totally 160 kg N ha−1) was set in 2017, and another two reduced N levels for LOF top-dressing (LOF130 and LOF100) were included in 2018. Compared with CF, the LOF160, LOF130 and LOF100 achieved similar rice yields and showed significant improvements in NUE (19.4%, 25.5% and 34.4%, respectively). Furthermore, due to the specific N forms and the implementation practice of more splits and low split-dosage, the LOF fertigation significantly decreased the cumulative NH3 volatilization by 41.2%–67.7% and cumulative TDN leaching losses by 19.5%–44.1%. Although additional fertigation equipment investment is required, the LOF fertigation still improved the net economic benefits (NEB) by 10.4%–18.9% and the net economic and ecological benefit (NEEB) by 34.0%–54.9%, which primarily attributes to labor and fertilizer savings and the mitigation in environmental damage cost. This indicates that the use of recycled LOF as a substitute for chemical fertilizer can offer a promising option for delivering environmental and economic benefits of reduced chemical fertilizer use and industrial-agricultural pollution.

Deep Placement of Npk Briquette in Rice: Environment Friendly Technology for Sustainable Rice Production

Nine experiments were conducted at the Bangladesh Rice Research Institute (BRRI) farm, Gazipur, BRRI regional station, Sagardi, Barisal and farmers’ field of Barisal during Boro, T. Aus and T. Aman season, 2012 to evaluate the NPK briquette efficacy in rice production. Experimental results revealed that deep placement of NPK briquette (2 x 2.4 g) increased rice grain yield about 10 % and it saves 51, 9 and 20 kg NPK ha-1 than BRRI fertilizer recommended rate in Boro season. Similarly, NPK briquette (1 x 3.4 g) produced 28 and 18% more rice grain yield than BRRI fertilizer recommended rate with a savings of 29 kg N and 7 kg K ha-1 in T. Aus and T. Aman season, respectively. In general, deep placement method gave higher grain yield compared to conventional urea application. Undiscounted benefit cost ratio (BCR) was 1.44, 2.40 and 3.20 for Boro, T. Aus and T. Aman, respectively when comparing at the same rates of N application. Thus, use of NPK briquette over urea broadcast and incorporation was economically viable and efficient for rice cultivation. This method helps to reduce N loss through soil-water interface which plays a vital role in reducing environmental pollution.&#x0D; Bangladesh Agron. J. 2021, 24(2): 127-136

Drip fertigation improves seed cotton yield, water productivity and profitability of cotton raised under high density planting system in semi-arid environment

The wasteful system of flood irrigation being widely practiced for cotton production in India needs replacement by efficient irrigation systems for conserving water. Cotton productivity can be boosted by optimizing the nutrient and water application through modern resource conservation techniques. Therefore, a field experiment has been conducted during summer (Kharif) season of year 2016 and 2017 to investigate consequence of surface drip irrigation along with N fertilization on the growth and seed cotton yield (SCY) under recently introduced high density planting system (HDPS) in India. The experiment having combinations of 3 drip irrigation {60, 80 and 100% of crop evapo-transpiration (ETc)} and 3 N fertigation levels {125 (94 kg N), 100 (75 kg N) and 75% (56 kg N) of recommended N dose (RDN)} along with control (i.e. conventional practice of irrigation through surface flood and soil broadcasting of urea as 100% RDN i.e., 75 kg N ha-1) has been conducted in complete randomized block design replicated thrice. Drip irrigation scheduled at 0.8 ETc recorded 2.5 and 23.2% higher SCY (2509 kg ha-1) than 1.0 ETc and 0.6 ETc, respectively. Among N levels, highest SCY (2452 kg) was observed with 75 kg N application, whereas 56 kg N ha-1 recorded least. A combination of drip fertigation at 0.8 ETc and 100% RDN elucidated 11.6, 61.5, 13.9 %, and 42.9 % higher SCY, water use efficiency, nitrogen use efficiency and benefit: cost ratio than control, respectively. Drip fertigation at 1.0 ETc along with 100% RDN improved SCY by 7.3% over control.

Deep placement of nitrogen fertilizer in autumn improves N utilization by spring tea (Camellia sinensis L.)

AbstractBackgroundThe efficient use of fertilizers depends very much on their proper placement, and the effects of fertilizer placement on the woody perennial plant tea (Camellia sinensis L.) are not clearly understood.MethodsA 15N mini‐plot field experiment was conducted to investigate the effects of four common techniques of fertilizer placement techniques. 15N‐labeled urea was applied in October by surface broadcasting, surface broadcasting with 3–5 cm soil incorporation, shallow (3–5 cm), and deep (10–15 cm) side dressing (DSD). The proportion of N derived from 15N‐labeled fertilizer (Ndff%) was estimated in root, and soil samples were collected 15 and 43 days after fertilization (DAA15 and DAA43) and in young shoots collected in the following spring.ResultsMost fertilizer 15N was located in the soil near the placement position at DAA15 and 15N had moved downward but maintained a similar distribution in the soil profile at DAA43. The distribution of fibrous root Ndff% in the soil profile was very similar to that of soil Ndff%. DSD resulted in the highest shoot Ndff%, the estimated amount of 15N in young shoot derived from 15N‐label fertilizer (shoot 15N), and its percentage related to the amount of 15N‐labeled fertilizer input (REFN%). Thus, DSD of urea as basal application in autumn maintained a higher and prolonged N supply in the middle and deep soil layers, thereby improving fertilizer‐N absorption and utilization in the following spring tea. However, direct broadcasting of urea on the soil surface resulted in low N availability in the soil and utilization by tea plants.ConclusionOur results demonstrate that DSD of N fertilization should be recommended for tea planting to increase N use efficiency and reduce environmental losses in forms of runoff and volatilization.

Ammonia, methane and nitrous oxide emissions from furrow irrigated cotton crops from two nitrogen fertilisers and application methods

• Urea broadcast and fertigation were applied at a commercial irrigated cotton farm. • Gas emissions were measured by micrometeorological technique and OP-FTIR technique. • NH 3 flux from anhydrous NH 3 was 24% higher than broadcasting urea with irrigation. • Daily fluxes of CH 4 and N 2 O were both negative following both fertilisation events. Abstract Agricultural systems use nitrogen (N) fertilizers to improve crop nutrition and yield, but applied N can negatively impact the environment and human health due to the gases emitted during and after N application. There are few direct measurements of multiple gaseous emissions from N fertiliser applied to irrigated cotton farms. This study was conducted in a commercial cotton farm in NSW, Australia to measure gaseous emissions from two N fertilisation strategies (urea broadcast onto dry soil followed by irrigation, anhydrous ammonia injected into water at the main irrigation channel), with the N fertilizer rate of 27 kg N ha −1 for each application. Gas fluxes of ammonia (NH 3 ), methane (CH 4 ), and nitrous oxide (N 2 O) were measured simultaneously using an inverse-dispersion technique coupled with open-path Fourier transform infrared (OP-FTIR) spectroscopic technique, located 150 and 800 m from the input source of the irrigation water. We found that anhydrous ammonia injected into the irrigation water contributed to higher peak NH 3 emissions (0.79 ± 0.09 kg N ha −1 day −1 ) than broadcasting urea onto dry soil (-0.06 ± 0.02 kg N ha −1 day −1 ). When daily NH 3 fluxes were accumulated over 8 − 10 days, 24% of the applied N was lost as NH 3 during anhydrous ammonia application, but no N loss was detected over the course of measurement period from the broadcast urea followed by irrigation. The daily fluxes of CH 4 and N 2 O were both negative following both fertilisation events. Our study suggests that cotton farm managers should avoid the use of anhydrous NH 3 in irrigation water to mitigate the environmental impact, as well as low efficiency of N fertiliser use.

Evaluation of nitrogen fertilizer source and application method for dryland wheat

Optimizing nitrogen (N) fertilization is critical to ensure high-yield and high-quality wheat (Triticum aestivum L.) production while minimizing its environmental footprint and production costs. A two-yr field trial was conducted in a dryland research farm in Montana with a clay loam soil to evaluate the response of spring bread wheat (cv. Velva) and durum (Triticum durum Defs cv. Joppa) to N rate (45 vs. 90 kg ha−1), N source (urea vs. SuperU®), and application method (broadcast vs. banding). Compared to broadcast application, fertilizer banding reduced plant density by 6% without affecting the final grain yield. Nitrogen rate had a significant effect on grain yield. Neither nitrogen source nor application method affected grain yield when N was applied at 90 kg N ha−1. Grain yield increased from 3171 to 3652 kg ha−1 with increasing N rate from 45 to 90 kg ha−1 in the year with ample rainfall, whereas yield remained unchanged in the drier year. Protein concentration was higher in broadcasting treatment compared to banding at 90 kg N ha−1. However, at 45 kg N ha−1, protein concentration in the grain was not affected by method of application. The source of fertilizer did not show a significant effect on grain protein concentration. Our data indicated no agronomic benefit in using SuperU compared to conventional urea or banding fertilizer vs. broadcasting in this dryland system.

Aquifer lithology affects shallow groundwater quality more than nitrogen fertilizer form and placement method in an Iowa agricultural field

AbstractExcessive nutrient loss threatens local and regional water resources, and many midwestern U.S. states are adopting nutrient reduction strategies to reduce export of N and P. A common practice to reduce N loss is improved fertilizer management. In this study, we used a strip trial design to assess the effects of split N application form (urea and urea ammonium nitrate [UAN]) and placement method (broadcast, coulter, Y‐drop) on corn (Zea mays L.) yields and shallow groundwater quality at an agricultural field at Kirkwood Community College in Cedar Rapids, IA. Twelve shallow monitoring wells were installed within the production field and sampled 14 times across a corn–soybean [Glycine max (L.) Merr.] rotation. Results showed that split application of UAN applied with either coulter injection or Y‐drop method produced approximately 8–11% higher corn yields than broadcast urea, but no statistically significant relation was found between groundwater quality and N form and placement method. Instead, we report that groundwater quality and levels were significantly influenced by variations in aquifer lithology. Groundwater within fine‐textured glacial till had significantly higher dissolved reactive P, SO4, and specific conductivity, whereas groundwater within the sand aquifer had a deeper water table and had higher NO3–N and dissolved oxygen. Study results suggest aquifer lithology can play a much larger role than varying the N form and application method on shallow groundwater quality in agricultural fields.

Identifying N fertilizer management strategies to reduce ammonia volatilization: Towards a site-specific approach

Concerns about ammonia (NH3) losses from nitrogen (N) mineral fertilizers have forced policymakers to set emission reduction commitments across Europe. Although best available techniques (BATs) have been recommended, large uncertainties still exist due to poorly targeted site-specific approaches that might compromise their effectiveness. Here we proposed and tested a conceptual framework designed to identify most effective BATs that reduce NH3 at the site-specific level. The study was conducted in the Veneto region, northeast Italy. After the mapping of NH3 emission potential areas, BATs and business-as-usual N fertilization scenarios were assessed using a modified version of the DNDC agroecosystem model and compared with urea broadcast distribution under different pedo-climatic conditions. The most promising practices were further tested in a field experiment using a wind tunnel combined with a FTIR gas analyzer. Results showed that closed-slot injection reduced NH3 emissions with any type of mineral or organic fertilizers. Injected application, with ammonium nitrate or organic fertilizers, reduced NH3 loss in maize by 75% and 96%, respectively, and in winter wheat by 87% and 98%, compared to surface broadcast. Injection was the most promising technology to support, being already available to farmers. However, some increase in nitrate leaching was observed, mostly in case of winter wheat (+24% for AN injection; +89% for organic fertilizers). By contrast, urea incorporation with hoeing, the most common technique used by farmers in spring crops, did not show satisfactory results, because the partial burial of urea caused strong NH3 emissions that were even higher compared to surface broadcast. Recommended NH3 reduction techniques should be tailored to local pedo-climatic and management conditions, and evaluated, in a holistic approach, considering all N fluxes in the environment.

Impacts of ammonia volatilization from broadcast urea on winter wheat production

AbstractAmmonia (NH3) volatilization from broadcast urea may lead to significant N losses in winter wheat. We aimed to: (a) quantify N losses through NH3 volatilization from fields fertilized with urea and urea amended with a urease inhibitor (NBPT) under cold weather months (February–April), and (b) investigate the impact of N losses through NH3 volatilization on the winter wheat production. We employed the integrated horizontal flux (IHF) method with passive NH3 samplers to quantify NH3 volatilization at five sites in Kansas. Urea and urea + NBPT were broadcast at a rate of 60 kg N ha–1 over circular plots. We assessed the impact of NH3 losses on wheat at three sites employing different rates of urea and urea + NBPT. NH3 losses volatilization varied from 0.3 to 29.6% of total N applied. The largest N losses (&gt;23% of applied N) occurred when urea was broadcasted to moist soils followed by a dry period. Amending urea with NBPT reduced NH3 volatilization losses by more than 20% on the campaigns with the largest N losses (&gt;23%). However, our results showed no significant differences for wheat yield, N‐recovery and agronomic efficiency between urea and urea + NBPT treatments likely due to the reduced NH3 volatilization (&lt;17%) where the impact on winter wheat was measured. Our results suggest that winter wheat farmers should carefully evaluate the soil surface moisture conditions before broadcasting urea to avoid potential NH3 volatilization losses even under cold conditions (average soil temperature ranging from 2.5 to 7.7 °C).