Surface Broadcast Research Articles

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.

Effects of potassium application on growth, yield, and quality of dryland cotton

AbstractPotassium (K) deficiency reduces cotton (Gossypium hirsutum L.) growth, development, lint yield, and fiber quality. The study's objective was to compare the effects of K fertilizer rate on cotton plant height (CPH), yield, and fiber quality in three cotton cultivars. Three cotton cultivars studied were NG 5711 B3XF (C1), PHY 480 W3FE (C2), and FM 1953GLTP (C3). Granular K fertilizer was surface broadcast and incorporated 1 week before planting at 34, 50, and 67 kg ha−1. The CPH and canopy width were measured from 30 to 105 days after planting. The cotton CPH increased by 13%, 17%, and 12% in 2020 and by 6%, 4%, and 8% in 2021 with 34, 50, and 67 kg ha−1 K fertilizer rates compared to control. The K application increased cotton canopy width by 39% in 2021 compared to 2020. The K application at 50 kg ha−1 yielded significantly more cotton yield than the control in 2020. The cotton lint yield increased by 25%, 34%, and 9% in 2020 and by 4%, 17%, and 11% in 2021 with 34, 50, and 67 kg ha−1 K fertilizer application rates than control. The cotton fiber staple length and color grade increased significantly with the 50 kg ha−1 K application rate than the control in 2020. Cultivars significantly impacted Col‐Rd and Col‐b in 2020 and 2021. This study shows that fertilizer‐K application improves not only yield, but also staple length and color grade in rainfed cotton crops.

Enhancing Yield and Nitrogen Utilization of Boro Rice with Urea Super Granules

A field experiment was conducted at the Soil Science Field Laboratory of Bangladesh Agricultural University, Mymensingh during boro season to assess the comparative performance of prilled urea (PU) and urea super granule (USG) on the growth, yield, and nitrogen uptake of BRRI dhan29. The experiment was laid out in a randomized complete block design with three replications. The treatment combinations were T1: Control, T2: PU at 7 days after transplanting (DAT)+27 DAT+47 DAT, T3: PU at 10 DAT+30 DAT+50 DAT, T4: PU at 15 DAT+35 DAT+55 DAT, T5: USG at transplanting, T6: USG at 7 DAT, T7: USG at 10 DAT and T8: USG at 10 DAT+30 DAT where PU and USG were applied @ 216 kg N ha-1. PU was applied as surface broadcasting whereas USG was placed at 6-8 cm depth by hand between four hills at every alternate row. The results revealed that all the treatments showed better performances than control (T1). Results found that yield components, yield, and nitrogen uptake of BRRI dhan29 responded significantly to deep placement of USG than PU. Treatment T6 (USG at 7 DAT) produced the highest grain and straw yields of 6.56 t ha-1 and 6.95 t ha-1 respectively. Treatment T6 (USG at 7 DAT) also showed the highest grain yield increase (57.16%) and straw yield increase (52.37%) over control. The highest grain, straw, and total N uptake of 87.28, 32.71 and 120 kg ha-1 respectively were obtained in the treatment T6 (USG at 7 DAT). The overall results clearly indicate that deep placement of USG at 7 DAT in rice field increases rice yield and efficient uptake of the applied N. So, treatment T6 (USG at 7 DAT) could be recommended as best treatment for reducing N losses, conserving environment and improving sustainable production of rice.

Preferential flow of phosphorus and nitrogen under steady‐state saturated conditions

AbstractRepeated broiler litter application on agricultural lands can cause nutrient enrichment of subsurface effluent, especially with the existence of preferential flow through soil macropores. Previous studies quantifying soil macropores have not attempted to establish a connection of soil macropore characteristics with the subsurface nutrient (nitrogen [N] and phosphorus [P]) losses, across different topographical locations in the field. This study investigated the effect of broiler litter application and preferential flow on subsurface nutrient transport (N and P) at different topographical positions (upslope, midslope, and downslope) in a no‐till pasture field located in Alabama, USA. Twelve intact soil columns (150 mm id and 500 mm length) were used, and the nutrient leaching measurements from laboratory experiments were linked to soil macropore characteristics quantified using X‐ray computed tomography image analysis and solute transport modeling. Treatments included surface broadcast broiler litter (5 Mg ha−1, on dry basis) and unamended control. Leachates were analyzed for dissolved reactive P (DRP), total P (TP), and nitrate + nitrite‐N (NO3− + NO2−–N). The bromide breakthrough curves provided evidence of preferential flow in all columns. Litter application significantly increased leachate P concentrations, and average TP and DRP concentrations were significantly higher in the leachate from upslope columns compared to those at downslope location. The NO3−–N concentrations in leachate exceeded the US EPA drinking water standard of 10 mg L−1 in all the treatment columns. The highest flow‐weighted mean concentrations of TP and DRP, at 2.7 and 2.5 mg L−1, respectively, were recorded in the upslope columns. Soil physicochemical properties and nutrient leaching losses varied substantially across topographical positions, indicating a need for variable litter application rates to reduce P build‐up and subsequent leaching in vulnerable locations within the field. The relevance of the effect of topographic position on nutrient leaching found in this study should be further tested by investigating a wider range of slopes and soil types in pastures.

Effect of high frequency subsurface drip fertigation on plant growth and agronomic nitrogen use efficiency of red cabbage

High emissions of nitrogen to the environment are one of the major drawbacks of modern agriculture. Subsurface drip fertigation (SDF) is a technology to apply fertilizer in small amounts continuously and directly into the root zone with the potential of mitigating deep percolation losses when accurately managed. Our study was established to analyze possible benefits of SDF, i.e. nitrate losses reduction without decrease in yield, as alternative to the conventional application of nitrogen fertilizer. In this five-year field study, effects of SDF on red cabbage (Brassica oleracea) growth, yield, root distribution and nitrogen uptake were evaluated. The experiments took place in northern Germany. Application of fertilizer in a solution with water was managed to match the needs of crops and placed directly in the root zone through permanently buried driplines. The outcomes of crop growth under SDF were compared with a control crop receiving fertilizer at one or two dates by surface broadcasting. Yield and agronomic nitrogen use efficiency were higher for crops grown under SDF. Total dry mass increase was especially high under dry conditions (34%) but as well under wet conditions with efficient management (20%). Head dry mass of crops grown under SDF had a stronger reaction to the available nitrogen than crops under conventional application, with values of 0.19 and 0.1 Mg ha-1 per kg N ha-1 respectively. Moreover, SDF treatment resulted on average ca. 14 kg ha−1 higher nitrogen uptake. In SDF plots, yield formation and nitrogen uptake was higher for plants grown directly above drip lines. Effect of the distance to nitrogen source was supported with numerical simulations. The root structure showed different distributions for the two treatments, particularly in years with low rainfall. Overall, the results showed the potential of SDF to effectively control nitrogen supply, thereby increasing yield formation of marketable plant organs.

Slurry acidification is as effective as slurry injection at reducing ammonia emissions without increasing N2O emissions: A short-term mesocosm study

Agriculture currently accounts for 90% of UK ammonia (NH3) emissions, however, national legally-binding targets are seeking to reduce this by 16% by 2030, relative to 2005 levels. One area which has been targeted to help achieve this target is the lowering of NH3 emissions during livestock manure handling and storage. Slurry acidification represents one potential strategy to abate NH3 throughout the slurry management chain, however, is not currently used in the UK. To address this knowledge gap, two mesocosm-scale experiments were set up to assess the potential for slurry acidification to reduce NH3 emissions at application and to measure impacts on NH3 emissions and short-term changes to soil mineral dynamics and N2O emissions. Experiment 1 determined the impacts of acidified cattle slurry (pH 6.5, 5.5, and 4.8) to conventional (non-acidified) slurry when simulating surface broadcasting. Experiment 2 assessed the impact of conventional and acidified slurry (pH 5.5) using simulated surface broadcasting and shallow injection of cattle slurry. Our results showed that acidification significantly abated NH3 (% of NH4-N applied) from 61.6% for conventional slurry to 26.6% at pH 5.5, and 2.5% at pH 4.8. Acidified surface broadcast was as effective at abating NH3 emissions to injected conventional slurry, and also delayed nitrification, while not significantly altering N2O emissions from conventional slurry. Our results strongly suggest that slurry acidification could be a viable strategy to help the UK reach its NH3 reduction target and exceed the current abatement potential through combining low emissions spreading techniques with acidification.

Residual Benefits of Poultry Litter Applied by Subsurface Band vs. Surface Broadcast to Cotton

Poultry litter (PL) is known to have residual effects on crop productivity long after applications cease. Whether this advantage is greater if applied by subsurface vs. surface broadcast is unknown. The objective of this study was to determine whether the residual benefit of PL to corn and cotton production is greater if applied in subsurface bands vs. surface broadcast and identify PL components contributing to this effect. The residual effect of PL applied by the two methods or synthetic nitrogen (sN) at seven plant available N rates (0–292 kg ha−1 yr−1) in 2014–2015 was tested on corn and cotton in 2016–2019. Corn was grown without applying PL or sN in 2016, and cotton was grown in 2017–2019 after applying 90 kg ha−1 yr−1 sN to all plots. Corn produced 40% greater grain and cotton produced 29% more lint yield due to residuals from PL than sN. Residuals from PL distinctly increased cotton leaf K over sN regardless of the method of application. Corn and cotton yield benefits from PL residual were greater if applied by subsurface banding vs. surface broadcast. This difference diminished with time. The overall results show PL components persist in the soil for up to 4 years and affect corn and cotton production, but this persistence is greater if the PL is applied by subsurface banding. This study identified K as the key PL nutrient that persisted in the soil and benefited cotton yield 4 years after the last application.

Integrated assessment of yield, nitrogen use efficiency and ecosystem economic benefits of use of controlled-release and common urea in ratoon rice production

Controlled-release urea (CRU) is commonly used to improve the crop yield and nitrogen use efficiency (NUE). However, few studies have investigated the effects of CRU in the ratoon rice system. Ratoon rice is the practice of obtaining a second harvest from tillers originating from the stubble of the previously harvested main crop. In this study, a 2-year field experiment using a randomized complete block design was conducted to determine the effects of CRU on the yield, NUE, and economic benefits of ratoon rice, including the main crop, to provide a theoretical basis for fertilization of ratoon rice. The experiment included four treatments: (i) no N fertilizer (CK); (ii) traditional practice with 5 applications of urea applied at different crop growth stages by surface broadcasting (FFP); (iii) one-time basal application of CRU (BF1); and (iv) one-time basal application of CRU combined with common urea (BF2). The BF1 and BF2 treatments significantly increased the main crop yield by 17.47 and 15.99% in 2019, and by 17.91 and 16.44% in 2020, respectively, compared with FFP treatment. The BF2 treatment achieved similar yield of the ratoon crop to the FFP treatment, whereas the BF1 treatment significantly increased the yield of the ratoon crop by 14.81% in 2019 and 12.21% in 2020 compared with the FFP treatment. The BF1 and BF2 treatments significantly improved the 2-year apparent N recovery efficiency, agronomic NUE, and partial factor productivity of applied N by 11.47–16.66, 27.31–44.49, and 9.23–15.60%, respectively, compared with FFP treatment. The BF1 and BF2 treatments reduced the chalky rice rate and chalkiness of main and ratoon crops relative to the FFP treatment. Furthermore, emergy analysis showed that the production efficiency of the BF treatments was higher than that of the FFP treatment. The BF treatments reduced labor input due to reduced fertilization times and improved the economic benefits of ratoon rice. Compared with the FFP treatment, the BF1 and BF2 treatments increased the net income by 14.21–16.87 and 23.76–25.96%, respectively. Overall, the one-time blending use of CRU and common urea should be encouraged to achieve high yield, high nitrogen use efficiency, and good quality of ratoon rice, which has low labor input and low apparent N loss.

Spacing of subsurface poultry litter bands: Influence on maize performance and nitrogen use efficiency

AbstractPoultry litter (PL) is traditionally surface broadcast to no‐till maize (Zea mays L.). PL is nutrient‐dense, and surface‐applied PL nitrogen (N) is vulnerable to losses to the atmosphere and water systems. An application method was developed by USDA‐ARS scientists for shallow subsurface banding PL to reduce ammonia (NH3) volatilization and surface runoff. There is limited information on how this application method will affect conservation and nutrient accessibility in no‐till maize. The objectives were to determine if adjusting PL lateral subsurface band placement in relation to maize rows affects nutrient use and maize yields. Treatments were a nontreated control (NTC), urea ammonium nitrate surface banded (Fert), poultry litter surface broadcast (PLBr), and three subsurface banded PL treatments. The subsurface PL treatments were one (PLSub1), two (PLSub2), or three (PLSub3) bands between maize rows. Treatments receiving N were applied at 180 kg total N ha−1. Nitrogen concentration in V4 aboveground dry matter was higher in PLSub1 than PLSub2. Aboveground dry matter yields for all PLSub treatments were greater than PLBr and comparable to Fert. The PLSub1 and PLSub2 treatments resulted in maize grain yields equivalent to Fert and greater than PLBr and NTC when averaged across years. Few differences were observed in postharvest soil sample nutrient concentrations between PLSub treatments. These results suggest that subsurface banding PL can conserve N and increase no‐till maize yield over traditional surface broadcast PL; however, increasing the frequency of subsurface PL bands did not clearly affect nutrient conservation or accessibility to the maize.

New phosphorus losses via tile drainage depend on fertilizer form, placement, and timing.

Agricultural phosphorus (P) losses are harmful to water quality, but knowledge gaps about the importance of fertilizer management practices on new (recently applied) sources of P may limit P loss mitigation efforts. Weighted regression models applied to subsurface tile drainage water quality data enabled estimating the new P losses associated with 155 P applications in Ohio and Indiana, USA. Daily discharge and dissolved reactive P (DRP) and total P (TP) loads were used to detect increases in P loss following each application which was considered new P. The magnitude of new P losses was small relative to fertilizer application rates, averaging 79.3g DRP ha-1 and 96.1g TP ha-1 , or<3% of P applied. The eight largest new P losses surpassed 330g DRP ha-1 or 575g TP ha-1 . New P loss mitigation strategies should focus on broadcast liquid manure applications; on average, manure applications caused greater new P losses than inorganic fertilizers, and surface broadcast applications were associated with greater new P losses than injected or incorporated applications. Late fall applications risked having large new P losses applications. On an annual basis, new P contributed an average of 14% of DRP and 5% of TP losses from tile drains, which is much less than previous studies that included surface runoff, suggesting that tile drainage is relatively buffered with regard to new P losses. Therefore old (preexisting soil P) P sources dominated tile drain P losses, and P loss reduction efforts will need to address this source.

Broadcast nitrogen application can negatively affect maize leaf area index and grain yield components under weed competition

Nitrogen (N) application and weed control play critical roles in the development of crops. In maize (Zea mays L.) cultivation, surface broadcast N application aiming at higher productivities is a common practice. However, N addition under weed competition could promote weeds rather than maize. To investigate this, a field study was developed over a Brazilian eutric nitisol for summer maize. We manipulated the presence (+) or absence (−) of surface broadcast N fertilization (NS) at the recommended dose (90 ​kg ​ha−1 N) and weed control (WC), obtaining the treatments NS+WC+, NS+WC−, NS−WC+, NS−WC−. We aimed to determine 1) whether maize could profit from N application even under weed competition, and 2) how treatments would affect maize's leaf area index and all grain yield components (cobs area−1, rows cob−1, grains row−1 and individual grain weight). We hypothesized that broadcast N application could jeopardize maize productivity by favoring weed development. Under no weed control, N application increased weed biomass by ∼58%, which resulted in reductions of 57% in leaf area index, 6.9% in rows per cob, 48% in grains per row, and 18.7% in grain weight. Ultimately, the grain yield (8216 ​kg ​ha−1) of the best performing treatment (NS+WC+) was 66% higher than that with the worst performance (NS+WC−), of 2797.3 ​kg ​ha−1. We conclude that in fertilized areas, weed control should be a priority, since the N applied under weed competition could be detrimental to maize's leaf area index, and affect most yield components and overall productivity.

Trade-offs in nutrient and sediment losses in tile drainage from no-till versus conventional till cropping systems.

Nutrient and soil loss from agricultural areas impair surface water quality globally. In the Great Lakes Region, increases in the frequency and magnitude of harmful and nuisance algal blooms in freshwater lakes have been linked to elevated phosphorus (P) losses from agricultural fields, some of which are transported via tile drainage. This study examined whether concentrations and loads of P fractions, total suspended sediments (TSS), nitrate (NO3 - ) and ammonium (NH4 + ) in tile drainage in a clay soil differed between a continuous no-till system combining cover crops and surface broadcast fertilizer (NTCC), and a more conventional tillage system with shallow tillage, fertilizer incorporation and limited use of cover crops (CT). Both sites had modest soil fertility levels. Year-round, high-frequency observations of tile drainage flow and chemistry are described over four full water years and related to management practices on the associated fields. There were similar water yields in tile drainage between the two systems; however, losses of TSS, particulate P (PP) and NO3 - were consistently greater from the CT site, which received larger quantities of fertilizer. In contrast, dissolved reactive P (DRP) losses were considerably greater from the NTCC site, offsetting the lower PP losses, such that there was little difference in TP losses between sites. Approximately 60% of the DRP losses from the NTCC site over the four years were associated with incidental losses following surface application of fertilizer in fall. This study provides insight into trade-offs in controlling losses of different nutrient fractions using different management systems. This article is protected by copyright. All rights reserved.

Towards efficient N cycling in intensive maize: role of cover crops and application methods of digestate liquid fraction

AbstractDigestate, a by‐product of biogas production, is widely recognized as a promising renewable nitrogen (N) source with high potential to replace synthetic fertilizers. Yet, inefficient digestate use can lead to pollutant N losses as ammonia (NH3) volatilization, nitrous oxide (N2O) emissions and nitrate () leaching. Cover crops (CCs) may reduce some of these losses and recycle the N back into the soil after incorporation, but the effect on the N balance depends on the CC species. In a one‐year field study, we tested two application methods (i.e., surface broadcasting, BDC; and shallow injection, INJ) of the liquid fraction of separated co‐digested cattle slurry (digestate liquid fraction [DLF]), combined with different winter cover crop (CC) options (i.e., rye, white mustard or bare fallow), as starter fertilizer for maize. Later, side‐dressing with urea was required to fulfil maize N‐requirements. We tested treatment effects on yield, N‐uptake, N‐use efficiency parameters, and N‐losses in the form of N2O emissions and leaching. CC development and biomass production were strongly affected by their contrasting frost tolerance, with spring‐regrowth for rye, while mustard was winter killed. After the CCs, injection of DLF increased N2O emissions significantly compared with BDC (emission factor of 2.69% vs. 1.66%). Nitrous oxide emissions accounted for a small part (11%–13%) of the overall yield‐scaled N losses (0.46–0.97 kg N Mg grain−1). The adoption of CCs reduced fall leaching, being 51% and 64% lower for mustard and rye than under bare soil. In addition, rye reduced leaching during spring and summer after termination by promoting N immobilization, thus leading to −57% lower annual leaching losses compared with mustard. DLF application method modified N‐loss pathways, but not the cumulative yield‐scaled N losses. Overall, these insights contribute to inform an evidence‐based design of cropping systems in which nutrients are recycled more efficiently.

Drilling of super large granular slow-release humic acid compound fertilizer improves simultaneously environmental and economic benefits in peach orchard

Large amounts of nitrogen (N) fertilizer were applied in fruit cropping system, resulting in overwhelming N loss to environment due to multiple fertilization and massive quick acting fertilizer applied with surface broadcast or other unreasonable employed methods. Super large granular slow-release humic acid compound fertilizer (SLF), as a new controlled release fertilizer, could be deeply placed nearby the tree roots and its nutrient release profile is parallel to the fruit development stages, while it has not been fully tested in fruit productions. To explore the environmental and economic performance of SLF a two-year field trial was performed in a peach orchard with three treatments: conventional fertilizer management with 521.1 kg N hm−2 yr−1 input (CM); SLF with 399.6 kg N hm−2 yr−1 input placed in 10 cm depth drilling holes (SLF1); SLF with 399.6 kg N hm−2 yr−1 input placed in 20 cm depth drilling holes (SLF2). The results showed that CM produced 21–25 kg N hm−2 yr−1 NH3 volatilization, 10–12 kg N hm−2 yr−1 N2O emission, and 14–32 kg N hm−2 yr−1 N runoff, with low fruit yield at 23–26 t hm−2. SLF2 efficiently reduced fertilizer N loss, especially mitigated NH3 volatilization by 47–57 %. In addition, SLF made a noticeable increase of peach fruit yield by 15–17 % and improved the number of harvest fruit by 9–11 %. Moreover, compared with CM, the SLF treatments increased fruit revenue by 14–19 %, lower the production cost about 3 % and improved the net economic benefits (NEB) by 24–29 %. Our results demonstrate that SLF placed in 20 cm drilling holes (SLF2) with twice fertilization could effectively reduce the environmental N loss, increase fruit yield, save labor cost and maximize net economic benefit. Therefore, replacing conventional fertilizer management with the saving-labor and facilitated SLF management in orchards is a viable alternative to improve N uptake efficiency, mitigate NH3 pollution, and achieve more economic income, further to provide a new perspective for the green development of fruit cropping systems.

Water quality benefits of weather-based manure application timing and manure placement strategies

The timing of manure application and placement of manure significantly affects manure nutrient use efficiency and the amount of nutrient lost from a field. Application of manure prior to a minimal precipitation period, and manure application through incorporation, reduces risks associated with nutrient loss through surface runoff. The current study aims to explore potential water quality impacts related to manure application strategies on the timing of application and approach (surface broadcasting or incorporation). The Soil and Water Assessment Tool (SWAT) was used to represent manure application scenarios and quantify potential water quality impacts in Susquehanna River Basin located in the Mid-Atlantic region of the United States. A baseline (business-as-usual) scenario was developed with manure application based on crop planting date and manure storage availability, and surface broadcasting as the application approach. The baseline was compared with a strategically timed manure application considering weather forecasting and manure incorporation. The strategic, weather-based manure application approach reduced TN and TP loading at the outlet by 4% and 6%, respectively. Manure incorporation simulations considering low-disturbance injection showed significant reduction of about 19% for TN and 44% for TP at the watershed outlet. Winter closure of manure application could reduce organic nutrient loss. Winter application of manure in 21% of row cropped areas (2% of whole watershed area) increased organic N and P loading by 10% and 4%, respectively, at watershed outlet.

Ammonia volatilisation losses from urea applied to acidic cropping soils is regulated by pH buffering capacity

Context Ammonia (NH3) volatilisation can be a significant nitrogen (N) loss pathway in the grains industry following the surface broadcast application of urea. However, the extent of urea volatilisation from acidic soils and the soil properties that regulate this N loss pathway have not been investigated widely. Aims We conducted a laboratory incubation experiment to measure NH3 volatilisation loss potential following the broadcast application of urea prills (1–2 mm diameter; 50 kg N ha−1) onto moistened acidic and neutral cropping soils, sampled from four long-term cropping research sites. Methods The selected soils varied in pH, clay content, organic carbon, pH buffering capacity (pHBC) and cation exchange capacity. Volatilised NH3 was captured in a phosphoric acid trap after 7, 14 and 21 days and then measured using colorimetric analysis. We compared the measured NH3 losses with predicted NH3 losses derived from an existing empirical NH3 volatilisation prediction model. Key results Of the applied urea-N, 0.9–25% was volatilised. Cumulative NH3 losses were strongly related (R2 = 0.77) with soil pHBC derived from a pedotransfer function. The existing NH3 loss model generally had poor predictive capacity (RMSE = 34%). Conclusions Using clay content as a surrogate variable for pHBC in the predictive model for sandy kaolinitic soils where it is largely a function of organic carbon content can cause poor estimates of NH3 volatilisation loss potential. Implications Grain production on sandy, acidic soils with low pHBC could lead to substantial NH3 volatilisation losses if urea is broadcast.

Evaluation of phosphorus runoff from sandy soils under conservation tillage with surface broadcasted recovered phosphates

Potential new sources of phosphorus (P) fertilizer are the recovered P from livestock wastewater through chemical precipitation and the ash from combusting animal manures. Although most of the research on P losses from conservation tillage include high water-soluble P compounds from commercial fertilizer sources, information on the use of non-conventional, low water-soluble, recycled P sources is scarce. Particularly for sandy soils of the United States (US) Southeastern Coastal Plain region, research driven information on P loss into the environment is needed to determine recommendations for a direct use of new recycled P sources as crop P fertilizers. The objective of this study is to investigate the potential P runoff from sandy soils under conservation tillage, fertilized with recovered P from liquid swine manure and turkey litter ash in comparison with commercial P fertilizer triple superphosphate (TSP). The field study included two typical sandy soils of the US Southeastern Coastal Plain region, the Noboco and Norfolk. Simulated rain corresponding to the annual 30-min rainfall in the study site (Florence County, South Carolina) was applied to plots treated with recovered P from liquid swine manure, turkey litter ash, and TSP, including a control with no P added. The runoff was monitored and sampled every 5 min during the test and composite soil samples were collected from the top (0–15 cm) and subsurface (15–30 cm) soil layers in each plot. Laboratory analyses were conducted to quantify both total P (TP) and soluble reactive P (SRP) in runoff samples, and the soil test P in the soil layers. Two-way analyses of variances show significant treatment effects on both TP and SRP runoff. The quantities of SRP runoff from plots treated with the recovered P from swine manure and turkey litter ash represent respectively 1% and 7–8% of SRP runoff from plots treated with TSP. Hence, the use of the recovered P materials as crop P fertilizers through surface broadcast application present less environmental risks compared to commercial TSP.

Precise delivery of nitrogen at tillering stage enhances grain yield and nitrogen use efficiency in double rice cropping systems of South China

Nitrogen fertilizer management substantially affects the growth, productivity, and nitrogen use efficiency (NUE) of rice production systems. To assess the effects of precise application of nitrogen fertilizer at tillering stage as ‘tillering-fertilizer’ on grain yield and nitrogen use efficiency, field trials were conducted in the late season of 2019 and 2020, in addition to a radioisotope 15 N tracer experiment. The experiment was comprised of four N fertilizer treatments i.e., no fertilizer application as a control (T1), traditional surface broadcast fertilization (90 kg N/ha as basal fertilizer and 60 kg N/ha as tillering fertilizer, T2), deep placement of tillering fertilizer (surface broadcast at 90 kg N/ha as basal fertilizer and 45 kg N/ha as tillering fertilizer at 10 cm depth, T3), deep placement of tillering fertilizer (surface broadcast at 90 kg N/ha as basal fertilizer and 30 kg N/ha as tillering fertilizer at 10 cm depth, T4) and two rice cultivars i.e., Wufengyou 615 and Yuxiangyouzhan . Results showed that grain yield remained 18.8% and 12.4% higher owing to increase in productive panicles and grain filling, 42.2% and 38.9% higher nitrogen agronomic efficiency, 4.6% and 10.4% higher nitrogen recovery efficiency, and 10.2% and 7.8% higher nitrogen physiological efficiency in T3 than T2 for Wufengyou 615 and Yuxiangyouzhan , respectively. Moreover, nitrogen derived from fertilizer in T3 was increased by 8.0% and 4.4% compared to T2 for Wufengyou 615 and Yuxiangyouzhan , respectively whereas the residual rate of T3 was increased by 31.5%. In addition, the T3 treatment substantially enhanced the leaf area index and leaf chlorophyll content that led to improved photosynthesis and the activities of enzymes related to nitrogen metabolism. Overall, 45 kg N/ha as tillering fertilizer at 10 cm depth and surface broadcast at 90 kg N/ha as basal fertilizer can improve grain yield as well as nitrogen use efficiency in late season rice production system of South China. • Precise delivery of nitrogen (PDN) at tillering stage (TS) can enhance grain yield in rice. • PDN at TS can improve nitrogen use efficiency in rice. • PDN at TS can increase nitrogen residual rate in the soil and decrease nitrogen unaccounted rate.

Subsurface banding of blended controlled-release urea can optimize rice yields while minimizing yield-scaled greenhouse gas emissions

Controlled-release urea (CRU) is widely reported to supply crop nitrogen (N) demand with one basal application, thus effectively replacing split applications of urea without diminishing grain yield and N use efficiency (NUE). However, its use for replacement for high-yield split applications of urea (CK) for rice is untested. In addition, the degree to which greenhouse gas (GHG) emissions in rice systems are affected when CRU is substituted for CK remains unclear. During 2017 and 2018, we sampled plant growth and gas emissions in a rice paddy field treated with three CRU types (sulfur-coated urea [SCU], polymer-coated urea [PCU], and bulk blended CRU [BBU]) applied via two methods (surface broadcasting on the soil and subsurface banding at 5 cm depth), with CK as a control. The three CRUs led to different soil NH4+-N dynamics, and the N supply pattern under BBU was more beneficial for rice seedling establishment than under SCU and PCU, resulting in grain yield and NUE comparable to those under CK. CRU type showed no significant effect on either CH4 emissions or N2O emissions, and broadcast CRUs exhibited significantly higher total GHG emissions than CK. However, banded CRUs significantly reduced the total GHG emissions in comparison with broadcast CRUs, by 9.2% averaged across the two years. Reduced CH4 emissions, particularly during the period prior to the middle drainage, contributed largely to the GHG difference. With comparably high grain yield and low total GHG emissions, banded BBU showed a low yield-scaled GHG (GHG emissions divided by grain yield) comparable to that under CK in both years. Overall, our study suggested that N management synchronized with rice demand and contributing to a high NUE tended to minimize yield-scaled GHG. Broadcast CRU can hardly substitute for CK in terms of either grain yield or GHG emissions, but banded BBU is a promising N management strategy for sustaining rice production while minimizing environmental impacts.

Fertilization depth effect on mechanized direct-seeded winter rapeseed yield and fertilizer use efficiency.

Deep fertilization is effective for improving crop yield and fertilizer use efficiency. However, its impact on mechanized direct-seeded rapeseed and the optimal fertilization depth are poorly understood. A field experiment was conducted to evaluate the fertilization depth effect on mechanized direct-seeded rapeseed growth. Five treatments were designed: surface broadcast fertilizer, no fertilization, and fertilizer banded placement at soil depths of 5 (D5), 10 (D10), and 15 cm (D15). Compared with surface broadcast fertilizer, deep fertilization generally increased seed yield and partial factor productivity by 11.0%, agronomic efficiency (AE) by 22.7%, and recovery efficiency (RE) by 79.2% due to the increase of root mass density (16.8%), plant height (8.6%), height of the first branch (10.6%), stem diameter (22.4%), shoot biomass (16.1%), and shoot nitrogen (35.7%), phosphorus (29.7%), and potassium (26.2%) uptake. D10 had the highest seed yield, oil yield, fertilizer use efficiency, and economic benefits at different fertilization depth treatments. Compared with D5 and D15 respectively, D10 increased seed yield by 5.4% and 46.0%, oil yield by 7.7% and 50.5%, partial factor productivity by 5.4% and 46.0%, AE by 9.0% and 99.5%, RE of nitrogen by 48.9% and 34.9%, RE of phosphorus by 83.1% and 38.0%, and RE of potassium by 57.5% and 32.5%. The economic benefits of D10 were CNY 867.31 ha-1 and CNY 4864.23 ha-1 higher than D5 and D15 respectively. Considering rapeseed growth and its economic benefits, this study shows that 10cm is an appropriate placement depth with regard to mechanized direct-seeded winter rapeseed production. © 2022 Society of Chemical Industry.