Apparent N Recovery Research Articles

The environmental and agronomic benefits and trade-offs linked with the adoption alternate wetting and drying in temperate rice paddies

ContextAlternating wetting and drying (AWD) is an irrigation practice, alternative to continuous flooding, to improve the agro-environmental sustainability of rice cultivation. Benefits include reduction in water consumption, methane (CH4) emissions and arsenic (As) concentrations in grain. However, drainage periods during AWD can negatively affect nitrogen (N) use efficiency by the crop and grain yields, while increasing nitrous oxide (N2O) emissions and cadmium (Cd) contents in grain. ObjectiveThe objective of this study was to provide a holistic evaluation of AWD adoption in temperate rice cropping systems, including associated trade-offs. We hypothesized that the adoption of AWD in water seeded rice paddies can reduce the global warming potential (GWP) without affecting plant N uptake or introducing yield gaps, and also maintain a high quality of rice grain by limiting the uptake of metal(loid)s present in the soil, thereby resulting in an overall positive agro-environmental performance. MethodsIn a two-year field experiment in NW Italy two alternative irrigation practices involving water seeding followed by AWD management of different severity (AWDsafe and AWDstrong) were evaluated relative to the conventional water seeding and continuous flooding (WFL), comparing three different rice varieties. Yields and yield components, plant N uptake, apparent N recovery (ANR), metal(loid) concentrations in grain, and CH4 and N2O emissions were evaluated. ResultsAWDsafe and AWDstrong maintained or increased yields compared to WFL depending on varieties, despite an increase in sterility. There were no consistent differences in N uptake and ANR. Both AWDsafe and AWDstrong significantly reduce As concentration in grain, but significantly increase Cd and nickel (Ni). AWDsafe and AWDstrong reduced CH4 emissions by 45–55 % and 40–73 %, respectively, compared toWFL, while no increase in N2O emissions was observed. This resulted in a reduction in the GWP of 46 and 54 % with AWDsafe and AWDstrong, respectively. Conclusions and ImplicationsAWD was shown to be effective for mitigating GHG emissions from temperate rice cropping systems while maintaining high yield performance comparable or higher than WFL. AWD may represent a viable alternative to continuous flooding to improve agro-environmental sustainability of temperate rice cropping systems, but the trade-off between decreasing As and increasing Cd and Ni contents in the grain may represent an important concern for food safety with the adoption of this alternative water management practice.

The effects of fertilizer pretreatment on nitrogen cycling in an intensively managed temperate grassland

Effective nitrogen (N) management is essential for minimizing fertilizer nutrient losses and maximizing N use efficiency. This study, conducted over two years on permanent grassland sites in Schleswig-Holstein, Germany, explored the effects of urea treatment with a urease inhibitor and digestate acidification on N-cycling and yield performance in a temperate maritime grassland context. Micro plots within these grasslands received varying N rates via acidified (with sulphuric acid) or non-acidified digestate (biogas residues), urea treated with- or without urease inhibitor (N-(n-butyl) thiophosphoric triamide) or calcium ammonium nitrate. Parameters measured included dry and N matter accumulations, NH3 volatilization, N2O emissions, NO3--N leaching, methane (CH4), and total greenhouse gas (GHG) emissions from soils. The findings demonstrated that the acidified digestate consistently enhanced metabolizable energy (ME), N yields (up to 47 %) and the apparent N recovery (ANR). While the acidified digestate and treated urea concurrently reduced NH3 emissions, the treated urea did not significantly affect (p> 0.05) dry matter (DM) and N yields, ANR, or total GHG emissions. Thus, digestate acidification or urea N stabilization could effectively mitigate the environmental impact of forage grass production while maintaining higher or comparable yields. However, higher risks of pollution swapping to groundwater bodies may result from higher N input rates. Applying acidified digestate or stabilized urea N to grasslands at a 120 kg mineral N ha−1 rate offers a practical approach, yielding appreciable N and ME while minimizing N losses.

Sewage Sludge Increased Lettuce Yields by Releasing Valuable Nutrients While Keeping Heavy Metals in Soil and Plants at Levels Well below International Legislative Limits

Sewage sludge can be used as an organic amendment as long as it is ensured that there is no risk of environmental contamination or risk to public health. In this study, sewage sludge from two wastewater treatment plants (WWTPs) subjected to two disinfection and stabilization treatments [40% (mass/mass), calcium oxide, and calcium hydroxide] and their respective untreated sewage sludge were used. Three control treatments were also added: conventional farmyard manure (FYM), a nitrogen (N) mineral fertilizer (ammonium nitrate 34.5% N) applied at a rate of 50 kg N ha−1 (N50) (the same rate of all organic amendments), and an unfertilized control (N0), totaling nine treatments. Lettuce (Lactuca sativa L.) was cultivated in pots for two growing cycles. The dry matter yield (DMY) was higher in the N50 treatment (13.5 and 10.6 g plant−1 in the first and second growing cycles, respectively), followed by sewage sludge (10.8 to 12.4 and 8.4 to 8.7 g plant−1), FYM (8.5 and 7.2 g plant−1), and the control (7.7 and 6.0 g plant−1). The DMY was related to the N provided by the different treatments, assessed by the N and nitrate concentrations in tissues, N uptake, and apparent N recovery (ANR). Sewage sludge, due to its high N concentration and low carbon (C)/N ratio, mineralized rapidly, providing a significant amount of N to plants, as well as other nutrients, such as phosphorus (P) and boron (B). FYM, with a higher C/N ratio, provided less N to plants, also due to the short duration of the lettuce growing cycle. Alkalized sewage sludge increased soil pH and calcium (Ca) availability for plants. Fertilizer treatments minimally influenced cationic micronutrients. Heavy metals in the initial sewage sludge were below the threshold values established in international legislation, and the levels in soil and lettuce tissues were generally not higher than those in other treatments. Both of the sewage sludges used in this study showed high fertilizing value and very reactive behavior, making nutrients available much more quickly than FYM. This information is relevant to consider in defining their agricultural use.

Toxicity of ZnO and Fe2O3 nano-agro-chemicals to soil microbial activities, nitrogen utilization, and associated human health risks

BackgroundVarious nano-enabled agrochemicals are being extensively used for soil remediation and to boost crop production by increasing the nutrient efficiency of fertilizers. However, understanding of their potential risks on the manure–soil–plant continuum is limited. These nano-agrochemicals can be potentially toxic to soil microbes and their associated functions, such as nitrogen (N) mineralization and decomposition of organic materials. Moreover, the accumulation of nanoparticles (NPs) in edible crops may reduce food quality, and can cause serious threats to human health. Accordingly, here we investigated how zinc (ZONPs) and iron oxide (IONPs) nanoparticles affect the soil microbial communities, their efficiency of decomposition and N mineralization, radish yield, and plant N recovery after soil application of poultry manure (PM). Furthermore, we studied the associated health risks (DIM, HRI) via dietary intake of radish.ResultsSoil application of ZONPs and IONPs significantly (P < 0.05) increased microbial biomass Zn/Fe indicating their microbial utilization. This decreased the colony-forming units (CFU) of bacteria and fungi. For example, the application of PM with ZONPs and IONPs decreased the CFU of bacteria by 32% and 19%, respectively. In case of fungi, the CFU reductions were slightly different (ZONPs: 28% and IONPs: 23%). Consequently, the N mineralization significantly decreased by 62% and 29% due to ZONPs and IONPs, respectively. Which ultimately resulted in the reduction of radish dry matter yield by 22% and 12%. The respective reductions of the apparent N recovery (ANR) were 65% and 39%. Health risk assessment indicated that DIM and HRI values from both the NPs lie under safe limits.ConclusionsWe conclude that both metal oxide nanoparticles (i.e., ZONPs and IONPs) can significantly affect the soil microbial community, their associated functions, and crop yield with the former being relatively more toxic. However, no evidence was found regarding the health risks to humans via dietary radish intake. These toxicological effects imply restricting the widespread production and use of NPs, and developing strategies for their safe disposal to avoid their contact with soil beneficial microorganisms.

Yield, nitrogen-use efficiency, and distribution of nitrate-nitrogen in the soil profile as influenced by irrigation and fertilizer nitrogen levels under zero-till wheat in the eastern Indo-Gangetic plains of India

Due to the introduction of zero-till wheat in the Indo-Gangetic plains (IGP) in India, irrigation and fertilizer nitrogen (N) management needs to be modified from that followed under conventionally tilled fields. A field experiment was conducted to study the effect of irrigation and N levels on yield and N uptake by zero-till wheat, fertilizer N-use efficiency, and distribution of nitrate-N (NO3-N) in a soil profile under zero-till conditions in an acidic alluvial soil of the eastern IGP. The experiment was laid out in a split-plot design with four levels of irrigation as main plots (I0-no irrigation, rain-fed, I1-122 mm in one irrigation at 21 days after sowing (DAS), I2-263 mm in two irrigations at 21 and 42 DAS, and I3-386 mm in three irrigations at 21, 42, and 84 DAS) and 4 N levels [0 (N0), 60 (N1), 120 (N2), and 150 (N3) kg N ha−1] as subplots. Grain and straw yields were significantly higher at the irrigation level-I2 and 120 kg N ha−1-N2 over the control (I0 and N0) and were at par with the highest applied levels of irrigation and N (I3 and N3). The nitrogen uptake by wheat followed a trend similar to yield for irrigation levels; however, it increased significantly up to 150 kg N ha−1. After the harvest of wheat crop, more NO3-N was observed in the 60–90 cm subsurface soil layer than in the surface 0–15 cm and/or 15–30 cm and 30–60 cm subsurface soil layers. The highest NO3-N concentration was recorded in the treatment I2N2. Accumulation of NO3-N in the soil increased up to irrigation levels I2 and with increasing doses of fertilizer N application. Combined applications of irrigation and N had a positive and significant influence on agronomic efficiency (AE) and apparent N recovery (ANR) but had no significant effect on physiological efficiency (PE). This study suggests that an appropriate combination of irrigation and N levels in zero-till wheat can lead to not only high-yield levels and N-use efficiency but also adequately control NO3-N leaching under acidic alluvial soils in the eastern IGP.

Real-time nitrogen management using decision support-tools increases nitrogen use efficiency of rice

Several decision support tools have been proposed for precision nitrogen (N) fertilizer application in rice (Oryza sativa L.) to increase nitrogen use efficiency (NUE) and grain yields. However, a comparison of their effectiveness has not been well documented. A field experiment was conducted in western Terai of Nepal during 2017–2018 to identify the appropriate decision support tool for improving NUE and grain yields. Nine N fertilizer management treatments were laid out in a randomized complete block design with three replications. The treatments included a GreenSeeker (GS) optical sensor, soil plant analysis development (SPAD) meter, leaf color chart (LCC), each of these treatments with basal application of N at 25 kg ha−1, urea briquette deep placement (UDP), and the existing government-recommended practice (RP, 100 kg N ha−1). N fertilizer application guided by decision support tools had a significant (p < 0.05) effect on grain yields. UDP produced the highest grain yield (6.80 Mg ha−1) among the treatments. Grain yields were not significantly different among GS, LCC (in combination with basal 25 kg N ha−1), RP, and UDP treatments. However, GS, UDP, and LCC saved N input by 54%, 22%, and 21%, respectively, compared to RP. In addition, GS produced a significantly higher agronomic N use efficiency (ANUE), partial factor productivity of N (PFPN), apparent N recovery (ANR), and utilization efficiency of N (UEN) compared to RP. These results suggest that application of N fertilizer guided by the GS decision support tool can save significant amount of N fertilizer compared to the current RP without compromising grain yield.

Winter annual management to increase nutrient recovery and forage production on dairies

AbstractManagement of manure and cereal rye (Secale cereale L.) has implications for crop production and nutrient cycling. This 1‐yr, full‐factorial experiment conducted in Pennsylvania quantified the effects of three management factors—(a) rye management (RyeM; early‐terminated cover crop [CC] vs. double crop harvested a week later [DC]), (b) manure application method (ManM; unincorporated broadcast manure [BM] vs. shallow disk injected manure [IM]), and (c) fall field operation prioritization (priority; manure priority [MP] manure application in late September with rye planting in mid‐October vs. rye priority [RP], rye planting in late September with manure application in early November)—on rye biomass, nutrient recovery, and forage yield and the effect of ManM and priority on DC forage nutritive value in a rye–corn (Zea mays L.) cropping sequence. This experiment was intended to be a repeated 2‐yr study, but due to MP treatment rye crop failure in the second year, the resulting 1‐yr dataset was analyzed to assess priority effects. Prioritizing rye planting in the fall with DC increased total forage production and apparent N recovery (ANR) when manure was broadcast. These results highlight the value of prioritizing fall rye planting in DC systems to increase rye spring biomass and nutrient recovery when manure is broadcast. More experiments should be conducted on fall field operation timing to develop reliable recommendations.

Nitrogen Fertilizer Rate Affects Yield and Tuber Quality of Drip-Irrigated Tablestock Potatoes (Solanum tuberosum L.) Grown under Subtropical Conditions

The response to nitrogen (N) rate for two potato (Solanum tuberosum L.) cultivars grown in a sub-tropical climate was evaluated during two spring seasons. Early-maturing tablestock potato cultivars, ‘Fabula’ and ‘Red LaSoda’, were grown using surface-drip irrigation. N fertilizer was applied through irrigation drip tape at 0, 112, 224, and 336 kg ha−1 of N. There was no difference of aboveground and tuber biomass accumulation between N fertilizer rates from 112 to 336 kg ha−1 of N during both growing seasons. Seasonal differences were observed in N recovery efficiency; in Season 1, apparent N recovery (ANR) was significantly higher for N rates of 112 and 224 kg ha−1 N for ‘Fabula’ and 112 kg ha−1 of N for ‘Red LaSoda’, respectively. In Season 2, there was no significant difference between ANR values among N rates between 112 and 336 kg ha−1 of N, for both cultivars. There was a significant interaction of N rate and growing season on total and marketable yields. In Season 1, average total and marketable yields for both cultivars increased from 9.8 Mg ha−1 with no N applied, to 25.8 Mg ha−1 with 224 kg ha−1 of N; no significant differences were observed at higher N rates. In Season 2, high early season rainfall likely depleted available soil N, resulting in decreased N recovery efficiency of plants and significantly lower yield compared to the previous season. N-fertilizer rates above 224 kg ha−1 of N did not increase total or marketable yields in both seasons. High rainfall events at the beginning of the Season 2 likely caused N stress and reduced tuber yields by 54% compared to the previous season. Results also highlighted the dominant effect of environmental conditions, particularly rainfall, on tuber yield and harvest quality response to N fertigation rate.

Enhanced efficiency nitrogen fertilizers were not effective in reducing N2O emissions from a drip-irrigated cotton field in arid region of Northwestern China

Drip irrigation is an effective water-saving strategy for crop production in arid regions. However, limited information is available on how fertilizer nitrogen (N) management affects soil nitrous oxide (N2O) emission under drip irrigation. A two-year (2017–2018) field experiment was conducted in arid northwestern China to test management options of fertilizer N to reduce N2O emission and improve NUE of cotton (Gossypium hirsutum L.) under drip irrigation. Treatment included a factorial design of rate (120, 240 kg N ha−1) and source of N fertilizer (Urea, polymer-coated urea-ESN, stabilized urea with nitrification and urease inhibitors-SuperU), and an unfertilized Control. Urea was split-applied with irrigation water (fertigation) whereas ESN and SuperU were all side-banded at pre-plant. Crop yield and N uptake, soil mineral N concentrations, soil temperature and moisture, and N2O fluxes were determined. Across the two growing seasons, a single pre-plant application with ESN or SuperU significantly increased growing season cumulative N2O emissions (ƩN2O) by 29–47% and applied N-scaled emission factor (EF) by 57–83% compared to urea fertigation, irrespectively of application rate. In contrast, cotton yield, agronomic NUE, apparent N recovery (ANR), and yield-based N2O emission intensity (EI) were not affected by N source. Reducing N rate from 240 to 120 kg N ha−1 significantly decreased ƩN2O by 35% in 2017 and 36% in 2018 while simultaneously reduced cotton yield in both years. The increased N2O emissions with ESN and SuperU were attributed to greater availability of inorganic N resulted from one-time application at pre-plant and higher soil temperature. We concluded that fertigation with urea at the recommended rate is the best option to ensure agronomic productively and agronomic NUE with minimal risk of N2O emissions. In contrast, the benefit of enhanced efficiency N fertilizer is limited and recommendation on using of these products is challenging for arid croplands under drip irrigation.

Impact of nitrogen and phosphorous on biomass yield, nitrogen efficiency, and nutrient removal of perennial grasses for bioenergy

Perennial grasses are the promising source of bioenergy in South America which could provide several environmental benefits such as reduction in the greenhouse gasses emissions and reduction of nutrients and soil losses. Our objective was to determine the impact of N and P fertilization on biomass yield, N use efficiency (NUE), apparent N recovery (ANR), and nutrient removal (NR) on three perennial grasses: elephantgrass (Pennisetum purpureum Schum.), giant reed (Arundo donax L.), and switchgrass (Panicum virgatum L.). Four fertility treatments were evaluated in a 8-year field study in northwestern Uruguay: 1. control (No fertilizer), 2.100 kg N ha−1 year−1, 3.100 kg P2O5 ha−1 year−1, and 4.100 kg N + 100 kg P2O5 ha−1 year−1. Across years, elephantgrass had the highest biomass yield followed by giant reed and switchgrass (18.9, 16.3, and 14.1 Mg ha−1, respectively). Biomass yield increased 46% when N fertilizer was added, compared to the control. A low response was detected for P fertilization on all grasses, probably for initial P soil content (≥9 g kg−1). Elephantgrass had the highest NUE (70 kg kg−1 N), however, it had the highest total NR on these eight years (899, 226, and 2800 kg ha−1 for N–P–K, respectively) among the grasses, indicating a potential for increased fertilization input over time. Switchgrass had the lowest average ANR (19%) and NR (334, 45, and 166 kg ha−1, respectively). Therefore, even though switchgrass presented the lowest biomass yield, it is an excellent option as low-input bioenergies grass for temperate regions.

Nitrogen Use Efficiency and Gaseous Nitrogen Losses from the Concentrated Liquid Fraction of Pig Slurries

Processed manure can be an alternative source of nutrients for untreated manure and mineral fertilizers. Mineral concentrates (MCs) are derived from reversed osmosis of the liquid fraction of separated pig slurries. The emissions of ammonia (NH3) and nitrous oxide (N2O) from different (processed) manures and fertilizers were tested in an incubation experiment and a greenhouse experiment with grass as a test crop. Dry matter yields and nitrogen (N) uptake were also determined in the greenhouse experiment. Incorporation into the soil decreased on NH3 emission but increased N2O emission for all nitrogen products (mineral fertilizer, untreated slurry, MC, and solid fraction of separated slurry). Incorporation of both MC, slurries, and mineral fertilizers increased N2O emission in the incubation experiment. The lowest apparent N recovery (ANR) in the pot experiment with grass was obtained for incorporated pig slurry (30–39%) and surface-applied MC (33–38%), while the highest ANRs were obtained for liquid ammonium nitrate (45–53%) and acidified MC (43–55%). It is concluded that MCs have a similar N fertilizer value as mineral N fertilizers if NH3 emission is reduced by incorporation or acidification.

Composting of municipal solid waste by different methods improved the growth of vegetables and reduced the health risks of cadmium and lead.

Reutilization of putrescible municipal solid wastes (MSW) in agriculture can provide valuable plant nutrients. However, it may pose serious noncarcinogenic health risks for a human when contaminants, especially the heavy metals in MSW, end up in plants through the waste-soil-plant continuum. This study examined the effects of composting methods viz. aerobically (AC), anaerobically (ANC), and aerobic-anaerobically (AANC) composted MSW material on (i) fertilizer value: vegetable yield, nitrogen (N) mineralization, and apparent N recovery (ANR); and (ii) associated health risks: selected heavy metal concentration, daily intake of metals (DIM), health risk index (HRI), hazard index (HI), and target hazard quotient (THQ) when applied to a loamy soil. All the aforementioned compost materials were incorporated into the sandy loam soil filled in pots and carrot and spinach were cultivated for 85 and 90days, respectively. After soil application, between 51 and 56% of the applied organic N was mineralized from ANC material, while the values in case of AC and AANC were 26-31% and 34-40%, respectively. Consequently, dry matter yield and vegetable N uptake from composts were in the order ANC > AANC > AC (P < 0.05). Further, vegetable ANR was the highest from ANC (56 and 56%) than AANC (42 and 45%), and AC (30 and 33%) for spinach and carrot, respectively (P < 0.05). Interestingly, plant uptake of lead and cadmium was lowest from ANC as compared to AC or AANC (P < 0.05), irrespective of the vegetable type. Consequently, DIM, HRI, and THQ for these metals were substantially lower in the former as compared to the latter compost materials. Further, HI from ANC material was 50% lower over the unfertilized control indicating the absence of noncarcinogenic human health risks via vegetable intake. This all indicates that from viewpoint of sustainable waste recycling in agriculture, anaerobic composting is superior to the other composting methods.

Recovery of nutrients from the liquid fraction of digestate: Use of enriched zeolite and biochar as nitrogen fertilizers

AbstractThe liquid fraction after liquid/solid separation of biogas digestate has a high potential as a fertilizer due to its high nutrient concentration. However, the direct application of digestate in agricultural fields results in practical problems due to its voluminous nature. One solution to this could be to concentrate nutrients onto sorbents such as biochar or zeolites, which can subsequently be used as a fertilizer. This study investigated the ability of biochar and zeolite ‘clinoptilolite' enriched with digestate nutrients to supply nitrogen (N) when used as a fertilizer. A pot experiment with ryegrass was conducted to test the effect of a nutrient‐enriched biochar and clinoptilolite by determining plant biomass growth and N uptake. This included untreated biochar and clinoptilolite as controls and two levels of N application (15 and 45 mg N per pot) each at two initial loading ratios (low and high). Nutrient‐enriched biochar and clinoptilolite increased plant biomass yield (up to 1.02 and 2.39 g per pot) and N uptake (up to 11.23 and 39.94 mg N per pot) compared to the untreated sorbents treatments. Initial loading ratio had a significant effect on plant biomass response and apparent N recovery (ANR) for enriched clinoptilolite, and lower initial loading ratio improved plant growth. In contrast to clinoptilolite, higher initial loading ratio resulted in higher ANR. In conclusion, our results reveal that N released from enriched clinoptilolite and biochar could be taken up by the plants, clinoptilolite performed more effectively than biochar, and initial loading ratio affected the performance of the sorbents when used as a fertilizer.

Predicting soil N supply and yield parameters in peat grasslands

Considerable nitrogen (N) mineralization occurs in drained peat soils in use for dairy grassland, due to aerobic decomposition of soil organic matter (SOM). N losses may be limited by matching grass N uptake with N mineralization and by adapting on-farm fertilization schemes to soil N supply (SNS) and apparent N recovery (ANR). Previous attempts to predict SNS of peat grasslands from soil parameters have been unsuccessful, partly due to high variation in SNS between sites and years. In this paper, we present field data from twenty dairy grasslands on drained peat (29–65% SOM; Terric Histosols). Grass yield parameters (e.g. SNS and ANR) were compared with a comprehensive data set of soil biotic and abiotic properties measured at the start of the growing season, and with N mineralization calculated from this data. SNS ranged between 171 and 377 kg N ha−1 (mean: 264 kg N ha−1) during the growing season. Soil N mineralization estimated by laboratory incubation and by foodweb-based production ecological calculations gave similar mean values with slightly higher coefficients of variation, but correlations with SNS were not significant. Regression analysis with soil properties showed a positive correlation between SNS and soil Ca:Mg ratio and a negative correlation between fertilized grass yield and soil C:SOM ratio. No significant models were found for ANR. Based on our data and on literature, we conclude that these parameters indicate linkages between grass yield and soil physical-hydrological properties such as soil structure and water availability. In particular, the C:SOM ratio in these soils with high organic matter content may be an indicator of water repellency, and our results suggest that grass growth was limited by drought more than by nutrient availability.

Yield and Nitrogen Use of Irrigated Processing Potato in Response to Placement, Timing and Source of Nitrogen Fertilizer in Manitoba

Optimizing nitrogen (N) fertilizer management in irrigated potato (Solanum tuberosum L.) on coarse-textured soils is challenging. The “4R” nutrient stewardship framework of using N fertilizer at the right rate, right source, right placement and right time provides approaches to improve fertilizer use efficiency while maintaining or improving yield. This 3-years replicated field plot study evaluated effects from a series of N fertilization strategies including 10 combinations of sources, placement and timing, as well as fertigation, on irrigated processing potato (cv. Russet Burbank) grown for a total of five site-years in the Province of Manitoba, Canada. Treatments were designed to provide early to late availability of N to the potato crop. Nitrogen was applied to 80% of Provincial N recommendation to increase the likelihood of observing improved fertilizer use efficiency and effects of treatments on yields. Measurements were tuber yield, size distribution, specific gravity, hollow-heart rate, fertilizer apparent N recovery (ANR) and agronomic nitrogen use efficiency (NUE). Results showed differences in yield, quality, ANR and NUE between fertilizer treatments were generally very small or absent. Average tuber marketable yields for fertilizer treatments were significantly greater than those for the unfertilized control (P < 0.001). Split application of urea at planting and hilling, and urea at planting with fertigation occasionally increased tuber marketable yields on sites of coarse textured soils (P < 0.05). Use of polymer-coated urea (ESN) or stabilized urea with inhibitors (SuperU) did not affect yield, quality or N use of potato. Site-year difference (P < 0.001) were apparent for all measures highlighting the importance of soil and climatic conditions on agronomic and environmental effects of N management practices. The results indicate current grower practice of split urea application at planting and hilling and urea at planting following by in-season fertigation are sound. Results indicate growers could shift to the more convenient practice of ESN at planting without reducing yields. Absence of treatment effects suggests N was generally not a limiting factor for the current study, indicating that the current recommendation for potato production in Manitoba over-estimate site-specific crop N needs.

Early sowing increases nitrogen uptake and yields of winter wheat grown with cattle slurry or mineral fertilizers

AbstractThe current study evaluated the effect of sowing date (early, mid-August or timely, mid-September) on two winter wheat (Triticum aestivum L.) cultivars (Hereford, Mariboss) with different rates of nitrogen (N) (0–225 kg total N/ha) applied as animal manure (AM; cattle slurry) or mineral fertilizers (N: phosphorus: potassium; NPK). Overwinter plant N uptake and soil mineral N content were determined during 2014/15, while harvest yields (grain, straw, N content) were determined during 2014/15 and 2015/16. Overwinter uptake of N was 14 kg N/ha higher in early than in timely-sown wheat. Despite very different yield levels in 2015 and 2016 harvests, the advantage of early sowing on grain yields was similar (1.1 and 0.9 t/ha); straw yield benefits were greater in 2015 (1.7 t/ha more) than in 2016 (0.4 t/ha more). In 2015 and 2016, N offtake was 35 and 17 kg N/ha higher in early than in timely-sown wheat, respectively. The mineral N fertilizer value of cattle slurry averaged 50%. Early sowing increased the apparent N recovery (ANR) for wheat regardless of nutrient source. However, ANR was substantially higher for NPK (82% in 2015; 52% in 2016) than for AM (39% in 2015; 27% in 2016). Performance of the two cultivars did not differ consistently with respect to the effect of early sowing on crop yield, N concentration and offtake, or ANR. Within the north-west European climatic region, moving the sowing time of winter wheat from mid-September to mid-August provides a significant yield and N offtake benefit.

Bedding additives reduce ammonia emission and improve crop N uptake after soil application of solid cattle manure

This study examined the influences of three potential additives, i.e., lava meal, sandy soil top-layer and zeolite (used in animal bedding) amended solid cattle manures on (i) ammonia (NH3), dinitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) emissions and (ii) maize crop or grassland apparent N recovery (ANR). Diffusion samplers were installed at 20 cm height on grassland surface to measure the concentrations of NH3 from the manures. A photoacoustic gas monitor was used to quantitate the fluxes of N2O, CH4 and CO2 after manures’ incorporation into the maize-field. Herbage ANR was calculated from dry matter yield and N uptake of three successive harvests, while maize crop ANR was determined at cusp of juvenile stage, outset of grain filling as well as physiological maturity stages. Use of additives decreased the NH3 emission rates by about two-third from the manures applied on grassland surface than control untreated-manure. Total herbage ANR was more than doubled in treated manures and was 25% from manure amended with farm soil, 26% and 28% from zeolite and lava meal, respectively compared to 11% from control manure. In maize experiment, mean N2O and CO2 emission rates were the highest from the latter treatment but these rates were not differed from zero control in case of manures amended with farm soil or zeolite. However, mean CH4 emissions was not differed among all treatments during the whole measuring period. The highest maize crop ANR was obtained at the beginning of grain filling stage (11–40%), however ample lower crop recoveries (8–14%) were achieved at the final physiological maturity stage. This phenomenon was occurred due to leaf senescence N losses from maize crop during the period of grains filling. The lowest losses were observed from control manure at this stage. Hence, all additives decreased the N losses from animal manure and enhanced crop N uptake thus improved the agro-environmental worth of animal manure.

Ruminant Urine Increases Uptake but Decreases Relative Recovery of Nitrogen by Smooth Bromegrass

Core Ideas Forage mass and crude protein increase with N fertilizer rates up to 160 lb/acre in smooth bromegrass pastures. Smooth bromegrass responds even more so to urine from livestock grazing. Managers should encourage even grazing distribution across time to minimize nutrient losses from pastures. Understanding pasture responses to urine deposition remains limited. From 2011 to 2012, we investigated the effects of urine collected from ruminants and applied to N‐fertilized (0, 40, 80, 120, and 160 lb N/acre) plots (25 sq ft) of smooth bromegrass (Bromus inermis Leyss.) in eastern Nebraska. Urine was spread evenly across plots at both a volume (0.6 qt/sq ft) and N content (0.26 and 0.24 oz/qt) that simulated ruminant urine deposition in spring and resulted in an additional supply of 425 and 392 lb N/acre in 2011 and 2012, respectively. Control plots received the same volume of distilled water but no additional N. Response variables included forage mass, crude protein (CP) concentration, N uptake, apparent N recovery (ANR), and N use efficiency (NUE). In 2011, forage mass, CP, and N uptake increased linearly with N fertilizer rate and were 80, 30, and 135%, respectively, greater in urine‐treated than in distilled water–treated plots. In 2012, drought limited forage mass, and only urine impacted N responses. Apparent N recovery averaged 42% in urine‐treated and 63% in distilled water–treated plots in 2011 but did not differ between treatments in 2012, averaging 24%. Values for NUE did not differ among treatments and averaged 13.0 lb dry matter (DM)/lb N fertilizer applied in 2011 and 6.5 lb DM/lb N fertilizer applied in 2012. In years with favorable precipitation, producers can expect forage mass and CP to increase with fertilizer applications up to 160 lb N/acre. Optimum rates, though, would depend on production goals, nutritional needs of livestock, and fertilizer, land, and cattle prices.

Classification and assessment models of first year byproducts nitrogen plant-availability from literature data

Byproducts can provide an important amount of nutrients for crops and improve soils properties. According to their C/N, nitrogen (N) mineralization or immobilization may be observed after their application onto agricultural land. Therefore, an indicator is needed to assess byproducts N availability for crops. Thirty-seven studies from the scientific literature on N mineralization or immobilization after application to agricultural land under a wide range of climatic and experimental conditions were collected in order to elaborate models assessing non-composted byproducts N availability during the first growing season according to the C/N ratio. Four methods were used to evaluate N availability: incubation, apparent N recovery (ANR), relative N effectiveness (RNE) and fertilizer equivalence (FE). Since ANR was the model most related to C/N (R2=0.77), this model was used to define six categories of C/N. Results expressed in terms of FE were converted into RNE values. Although RNE is less precise than ANR, efficiencies of byproducts were expressed in terms of average RNE because it is the most appropriate for fertilization grids. Therefore, depending on C/N of non-composted byproducts, six categories were defined. i) high mineralization: +66% RNE and 5≤C/N, ii) moderate mineralization: +33% RNE and 5<C/N≤16, iii) low mineralization: +9% RNE and 16<C/N≤38, iv) low immobilization: −9% RNE and 38<C/N≤90, v) moderate immobilization: −27% RNE and 90<C/N≤140, and vi) high immobilization: −55% RNE and C/N>140.

Effect of Sesbania Incorporation as Nitrogen Source on Growth and Yield of Whole Crop Barley and Reduction of N Fertilizer in Saemangeum Reclaimed Tidal Land

It is known that the poor soil fertility of newly reclaimed saline soils is due to the lack of organic matter and available mineral nutrients for crop production. The effect of green manuring with Sesbania aculeata in combination with five rates of urea-N treatments (N0. N25, N50, N75, N100) on the productivity of a subsequent whole-crop barley and the fertility of the reclaimed saline soil in Saemangeum was evaluated in the field during 2013-2014 growing season. Sesbania was grown during summer season (June to October). The amount of Sesbania incorporated was 16.2 Mg ha -1 . Sesbania contributed to 393 kg N ha -1 to the soils when ploughed down and incorporated before whole-crop barley cultivated. The performances of whole-crop barley following sesbania incorporation were significantly affected by a combination of Sesbania manuring and different N rates. The N fertilizer equivalence without N fertilizer following Sesbania was 42.6% (63.9 kgN ha -1 ), compared with N100(150 kg N ha -1 ) in fallow soils. The whole-crop barley yield responded to N fertilizer rates in both sesbaniaamended and fallow soil. The yield response to nitrogen rates in fallow soil was linear (Y=0.0586X+3.3011, R 2 =0.9534), whereas that in sesbania-amended soils was quadratic (Y= -0.001X 2 +0.1322X+5.7143, R 2 =0.9576). The yield of whole-crop barley in sesbania-amended with increasing N rates was increased up to SN75 (115 kgN) 10.3 Mg ha -1 . Apparent N recovery (ANR) of whole-crop barely showed decreased with sesbania plus increasing rates of N fertilizer. Despite higher yield with sesbania manuring plus increasing N rates, the contributions of N from Sesbania with increasing N rates to whole-crop barley were decreased, whereas those from fertilizer increment due to excessively mineralized Nitrogen. Considering yield, ANR, N contribution from Sesbania and nitrogen fertilizer, the optimum N rate was N50 rate following sesbania incorporation.