Nitrogen Fertilizer Use Efficiency Research Articles

Biochar return in the rice season and straw mulching in the oilseed rape season achieve high nitrogen fertilizer use efficiency and low greenhouse gas emissions in paddy-upland rotations

Straw return can enhance crop yields and nitrogen fertilizer use efficiency (NFUE) in paddy-upland rotation systems. However, straw return in wetland rice systems can significantly increase CH4 emissions, which could be alleviated if the straw is converted to biochar before incorporation. This study investigated the effect of different crop residue management strategies on NFUE and greenhouse gas (GHG) emissions in a paddy-upland rotation over a four-year field experiment. We compared two treatments where all crop residues were removed (no N fertilizer (PK), recommended N fertilizer (NPK)) with three different methods of straw return. This included (i) direct straw return (NPK+S/S), where all crop residues were directly applied to the field after harvest; (ii) straw return as biochar (NPK+B/B), where all crop residues were converted into biochar before incorporation; (iii) straw return as biochar in the rice season and direct straw return in the oilseed rape season (NPK+B/S). Four-year crop yields, NFUE, two-year ammonia (NH3) volatilization, and GHG emissions were determined. The results showed that compared with the NPK treatment, straw and biochar return increased rice and oilseed rape yields by 0.41–0.80 t ha−1 and 0.24–0.33 t ha−1, respectively, and the annual NFUE by 4.3–6.9%. Direct straw return (NPK+S/S) did not significantly affect annual NH3 volatilization, but significantly increased cumulative N2O emissions (by 27.3%), CH4 (by 132.4%), global warming potential (GWP, by 75.2%) and greenhouse gas emissions intensity (GHGI, by 61.1%), respectively. In contrast, converting crop residues into biochar before incorporation significantly reduced annual NH3 volatilization and N2O and CH4 emissions. Compared with the NPK+S/S treatment, the NPK+B/B and NPK+B/S treatments reduced cumulative N2O by 20.5–26.7% and CH4 emissions by 56.5–65.9% with the corresponding reduction in GWP value (42.3–50.4%) and GHGI value (44.3–52.6%). Considering biochar production cost, we recommended straw return as biochar in the rice season and straw mulching in the upland season as a measure to increase crop yields and NFUE while reducing GHG emissions in the paddy-upland rotation.

Unexpected air pollutants with potential human health hazards: Nitrification inhibitors, biocides, and persistent organic substances

To better understand the influence of land use and meteorological parameters on air pollutants, we deployed passive air samplers in 15 regions with different land use in eastern Austria. The samplers consisted of polyurethane PUF and polyester PEF filter matrices, which were analyzed for 566 substances by gas-chromatography/mass-spectrometry. In a previous article, we highlighted a widespread contamination of ambient air with pesticides that depends on the surrounding land use and meteorological parameters. Here we report that, in addition to agricultural pesticides, eight other substances were frequently detected in ambient air: Nitrapyrin, a nitrification inhibitor used to increase nitrogen use efficiency of fertilizers and banned in Austria since 1993; biocides against insects (DEET and transfluthrin) used mainly outside agriculture; piperonyl butoxide (PBO), a synergist mixed into pesticide formulations; and four industrially used polychlorinated biphenyls (PCBs), long banned worldwide. Concentrations of the detected substances were positively related to air temperature, but only slightly related to agricultural land use in the sampler's vicinity. The city center showed the highest concentrations of biocides, PCBs and PBO, but also medium concentrations of nitrapyrin. Four sites had no air contamination with these substances; including two national parks dominated by grassland or forest, but also two sites with mixed land use. The potential human toxicity of the detected substances based on globally harmonized hazard classifications was high: seven substances had specific organ toxicity, six were cancerogenic, and two were acutely toxic; however, several substances had incomplete information of hazard profiles. Moreover, all substances were acutely and chronically toxic to aquatic life. We recommend that substances of different origins be included in the air pollution monitoring portfolio to comprehensively assess the potential hazards to humans and the environment.

Effects of Reducing Nitrogen Application Rate under Different Irrigation Methods on Grain Yield, Water and Nitrogen Utilization in Winter Wheat

We conducted a two-year field experiment on winter wheat (Triticum aestivum L.) from 2016–2018 to compare the effects of reducing nitrogen application rate in spring under three irrigation methods on grain yield (GY), water and nitrogen use efficiency in the North China Plain (NCP). Across the two years, GY of conventional irrigation (CI), micro-sprinkling irrigation (SI) and drip irrigation (DI) decreased by 6.35%, 9.84% and 6.83%, respectively, in the reduced nitrogen application rate (N45) than the recommended nitrogen application rate (N90). However, micro-irrigation (SI and DI) significantly increased GY relative to CI under the same nitrogen application rate, and no significant difference was observed in GY between SI and DI under N45, while SI obtained the highest GY under N90. The difference among different treatments in GY was mainly due to the variation in grain weight. The seasonal evapotranspiration (ET) in N45 was decreased more significantly than N90, and there was no significantly difference in ET among different irrigation methods under N45, but micro-irrigation significantly decreased the ET relative to CI under N90. Micro-irrigation significantly improved water use efficiency (WUE) compared to CI at the same nitrogen application rate. Under N45, compared with CI, WUE in SI and DI increased by 9.09% and 4.70%, respectively; however, the WUE increased by 15.9% and 7.23%, respectively, under N90. Reducing nitrogen application rate did not have a significant impact on WUE under CI, but it did have a substantial negative impact on SI and DI. Nitrogen accumulation in wheat plants at maturity (NAM) in N45 deceased significantly compared with N90 under the same irrigation method. Compared with CI under the same nitrogen application rate, micro-irrigation treatments significantly increased NAM, while SI was the largest. In comparison to N90, under three irrigation methods, N45 significantly increased nitrogen fertilizer use efficiency (NfUE). The highest NfUE was attained in SI, followed by DI, while CI was the lowest. Moreover, N45 significantly decreased soil NO3−-N accumulation (SNC) in three irrigation methods, and micro-irrigation significantly decreased the SNC in deep soil layers compared with CI when nitrogen is applied at the same level. Overall, micro-irrigation with a reduced nitrogen application rate in spring can achieve a relatively higher production of winter wheat while increasing the use efficiency of water and nitrogen and reducing soil NO3−-N leaching into deep soil layers in the NCP.

Biochar Optimizes Wheat Quality, Yield, and Nitrogen Acquisition in Low Fertile Calcareous Soil Treated With Organic and Mineral Nitrogen Fertilizers.

Crop quality and nutrient uptake are considerably influenced by fertilizers inputs and their application rate. Biochar (BC) improves nitrogen uptake and crop productivity. However, its interaction with synthetic and organic fertilizers in calcareous soil is not fully recognized. Therefore, we inspected the role of biochar (0, 10, 20, and 30 t ha–1) in improving N uptake and quality of wheat in a calcareous soil under integrated N management (90, 120, and 150 kg N ha–1) applied each from urea, farmyard manure (FYM) and poultry manure (PM) along with control) in 2 years field experiments. Application of 20 t BC along with 150 kg N ha–1 as poultry manure considerably improved wheat grain protein content (14.57%), grain (62.9%), straw (28.7%), and biological (38.4%) yield, grain, straw, and total N concentration by 14.6, 19.2, and 15.6% and their uptake by 84.6, 48.8, and 72.1%, respectively, over absolute control when averaged across the years. However, their impact was more pronounced in the 2nd year (2016–2017) after application compared to the 1st year (2015–2016). Therefore, for immediate crop benefits, it is recommended to use 20 t BC ha–1 once in 50 years for enhancing the nitrogen use efficiency of fertilizers and crop yield.

Effects of water saving and nitrogen reduction on the yield, quality, water and nitrogen use efficiency of Isatis indigotica in Hexi Oasis

Isatis indigotica planting is the backbone of the medicinal industry in Hexi Oasis, Gansu. In order to solve the problems insufficient water resources and excessive application of nitrogen fertilizer in this area, this paper explored the irrigation and nitrogen levels that can meet the multiple goals of Isatis indigotica. The two-factor split-plot field experiment (2018‒2019) was conducted in Minle County, Gansu Province, China, which contains 9 treatments. There were three levels of irrigation water: W1(low), W2(medium), and W3(high). The soil moisture contents were 60–70%, 70–80%, and 80–90% of the field water-holding capacity, respectively. The nitrogen application rate was classified into three levels, N1(low), N2(medium) and N3(high), which were 150, 200 and 250 kg N/ha, respectively. The standard local irrigation water amount and nitrogen application rate corresponded to W3N3. The results showed that the yield of Isatis indigotica increased first and then decreased with the increase of irrigation amount and nitrogen application rate, the yield of W2N2 is 12.2–17.1% higher than that of W1N1, the yield of W3N3 was 12.1–17.5% lower than that of W2N2. Saving water and reducing nitrogen can improve the quality of Isatis indigotica, compared with W3N3, the indigo, indirubin, (R,S)-epigoitrin and polysaccharides of W2N2 increased by 4.5–5.9%, 2.7–3.1%, 5.2–6.0%, and 1.8–2.1%, respectively. With the increase of nitrogen application rate, the water use efficiency (WUE) first increased and then decreased, as the irrigation volume increases, WUE decreases. Compared with W3N3, the WUE of W2N2 increased by 24.3–27.2%. With the increase of water input, the nitrogen fertilizer use efficiency (NUE) first increased and then decreased, as the nitrogen application rate increases, NUE decreases. Compared with W3N3, the NUE of W2W2 increased by 31.8–34.5%. Therefore, W2N2 can improve quality and increase water and nitrogen utilization efficiency on the basis of ensuring yield.

Evaluating the risks of nitrogen fertilizer-related grain production processes to ecosystem health in China

Globally, ecosystems are becoming damaged or degraded due to stresses associated with anthropogenic activities. To identify the quantitative connection between nitrogen fertilizer-related agricultural production processes and ecosystem health, a dose-response approach based on the ReCiPe 2016 method is developed. Rice production had the highest potential ecosystem health risk (EHR) (560 species.yr) in China, while maize and wheat had EHR values of 413 and 252 species.yr, respectively. Both crop type and planting area have great impacts on EHR. Pollutants posing the highest potential harm to ecosystem health were NH3, N2O, and NO3−. Air pollutants, including NH3 and N2O, did more severe damage to ecosystem health than soil or water pollutants. Scenario analysis suggests that if improved efficiency of nitrogen fertilizer use is employed to replace current practices, total EHR would decline by about 28.7- 41.1%. Improved farming practices could change the relationship between grain productivity and agroecosystem health from trade-offs to co-benefits. Results demonstrated that optimizing chemical fertilizer application in agricultural production processes could significantly contribute to the delivery of some Sustainable Development Goals. It suggests that the impacts of agricultural production on the atmospheric environment require further attention.

Review of research on INM and various weed control practices in rice (Oryza sativa L.)-Groundnut (Arachis hypogaea L.) cropping system under irrigated medium land situation

Rice-groundnut cropping system is one of the important cropping systems of India. Rice (Oryza sativa L.) is the staple food of the world. Rice is a heavy nitrogen feeder, but fertilizer nitrogen use-efficiency is very low under tropical conditions. Nutrient management provides an approach for feeding the plants with nutrients as and when required. It is therefore, necessary to apply fertilizer elements particularly N, P and K in optimal quantity to increase and sustain the productivity. A major portion of nitrogen in wetland soils occurs in organic pool, though this is usually low. Complementary use of organic and biological source of plant nutrient along with chemical fertilizer is of great importance for the maintenance of soil health and productivity. Sustainable cropping systems require crop yields should be stable through the maintenance of soil fertility and the balance of nutrients in the system. Increases in soil carbon levels require sustained periods of balanced fertilization and residue retention. Weed infestation in rice remains the largest constraint, limiting its productivity. Groundnut (Arachis hypogaea L.) is one of the most important edible oilseed crop extensively cultivated in the world. This groundnut is highly susceptible to weed infestation because of its initial slow growth habit up to 40 days after sowing, short plant height and underground pod bearing habit. In this review studies on the effect of integrated nutrient management and weed control practices on rice (Oryza sativa L.) – groundnut (Arachis hypogaea L.) cropping system are discussed. Judicious application of chemical fertiliser coupled with green manuring of Dhaincha and use of herbicides in rice as well as succeeding groundnut crop for management of weeds increases the productivity of the system.

Integrated use of farm manure and synthetic nitrogen fertilizer improves nitrogen use efficiency, yield and grain quality in wheat

Lower nitrogen use efficiency (NUE) is a major yield limiting factor in semi-arid regions due to poor organic contents of the soils. There is a close relationship between soil organic matter and NUE of fertilizers. Therefore, this study was conducted to assess the effect of sole N fertilizer and its combinations with organic amendments (farm manure combinations) on N use efficiency and crop productivity. For this purpose, a two-year field study was conducted to access the influence of integrated use of synthetic N fertilizer (urea) and farm manure on N use efficiency and wheat productivity. Treatments include i.e. Control, 100% N by Urea + 0%N by farm manure (FM), 75% N by Urea + 25 % N by FM, 50% N by Urea + 50% N by FM, 25% N by Urea + 75% N by FM, 0% N by Urea + 100% N by FM arranged in a triplicate randomized complete block design having recommended N rate of 150 kg ha–1. The results revealed that the treatment having 75% Urea and 25% FM followed by 50% Urea and 50% FM showed better results in term of wheat growth and yield. There was 98% increase in N uptake of wheat grains and 200% increase in NUE by the application of 75% urea+25% FM relative to sole application of urea. This study suggests use of 3:1 ratio of urea and FM for maximum NUE and sustainable wheat production.

Micro-irrigation improves grain yield and resource use efficiency by co-locating the roots and N-fertilizer distribution of winter wheat in the North China Plain

Water use efficiency (WUE) and nitrogen fertilizer use efficiency (NUE) of winter wheat are urgently needed to further improve in the North China Plain (NCP). In this study, a 3-year field experiment was conducted during the 2014–2017 growing seasons to clarify the effect of traditional flood irrigation (TI), surface drip irrigation (DI), and micro-sprinkling irrigation (MSI) on grain yield, WUE, and NUE of winter wheat. Across the 3 years, grain yield of DI and MSI improved by 9.79% and 14.1%, WUE of DI and MSI increased by 12.3% and 17.7%, and NUE of DI and MSI increased by 9.77% and 14.0%, respectively compared with those of TI. Wheat subjected to the micro-irrigation treatments (DI and MSI) had higher chlorophyll content in flag leaves 10 days post-anthesis; this postponed senescence of the flag leaves, which increased dry matter accumulation post-anthesis, and increased 1000-grain weight and grain yield. The micro-irrigation treatments reduced pre-anthesis water consumption but increased post-anthesis water consumption and ensured the water supply in the top soil layer at the critical stage, thus increasing WUE. Root length density (RLD) of TI in the 0–80-cm soil layer was significantly higher than that of micro-irrigation, whereas micro-irrigation had higher RLD than TI below the 80-cm soil layer, which promoted the absorption and utilization of water and nitrogen in deep soil. The micro-irrigation treatments increased total nitrogen accumulation of the plants, reduced soil nitrate nitrogen (NO3−-N) content at maturity, ensured the nitrogen supply in the top soil layer, thus increasing NUE. Overall, micro-irrigation with water and fertilizer as an integrated pattern significantly improved grain yield, WUE, and NUE of winter wheat in the NCP by co-locating the root, water, and N-fertilizer distribution and reducing NO3−-N accumulation in deep soil. The best treatment was micro-sprinkling irrigation.

THE IMPACT OF LIQUID BIO-GAS FERTILIZER ON FENNEL CROP PRODUCTIVITY AND OIL CONTENT UNDER DIFFERENT LEVELS OF IRRIGATION WATER

Two experiments were carried out at test and research station of Tractors and Farm machinery at Sabahia, Alexandria Governorate, Egypt during 2016/2017 season to study the effect of liquid Biogas fertilizer on vegetative growth, chemical composition and essential oil% on fennel plants. The remaining mixture of the process of fermentation of organic and exogenous waste from the fermentation is called the name of the biogas fertilizer. This fertilizer can be dried and converted into organic liquid or dry fertilizer and used in the fertilization of various agricultural crops very efficiently and because of its reliable price and dispense with mineral fertilizers which are expensive and harmful tohumans.The experimental design was split plot with three replicates. The main plots were conducted for two rates of liquid biogas fertilizer (15) and (25) m3 / fed with Three levels of concentration of biogas fertilizerlevel 1 (10%), Level 2 (20%) and Level 3 (30%) the subplots were occupied by three levels of irrigation (50%, 75% and 100%)from the maximum irrigation rate of 4000m3/fed . The main results could be summarized as follows (1) Application biogas liquid fertilizer level at 30% (25m3/Fed) gave the highest mean values of all studied characters under the third level of water irrigation (50%).Essential oil% and majors compound % for the Foeniculum vulgare tested in the study. The results also showed that the highest value for water use efficiency (WUE) was 0.56 for the treatment (Z2Q3I3) and the highest value for nitrogen fertilizer use efficiency (NUE)was 14.5 for the treatment (Z1Q1I3).However, all traits under study increased significantly due to biogas liquid fertilizer treatments over the control treatment

Improving Nitrogen Fertilizer Use Efficiency in Surface‐ and Overhead Sprinkler‐Irrigated Cotton in the Desert Southwest

Core Ideas Nitrogen use efficiency is low in surface‐irrigated cotton. Canopy reflectance can guide in‐season N management. Deep percolation of rain and irrigation is associated with nitrate leaching. Nitrogen fertilizer use efficiency (NUE) is low in surface‐irrigated cotton (Gossypium hirsutum L.), especially when adding N to irrigation water. A NO3 soil‐test algorithm was compared with canopy reflectance‐based N management with surface‐ overhead sprinkler‐irrigation in central Arizona. The surface irrigation studies also compared fertigation of N fertilizer with knifing‐in of N and the addition of a urease and nitrification inhibitor (Agrotain Plus, Koch Agronomic Services, Wichita, KS) to urea ammonium nitrate (UAN). Cotton lint and seed yields responded positively to N fertilizer in all four site‐years. Recovery efficiency (RE) of N at low N fertilizer rates (60 to 76 kg N ha–1) ranged from 21 to 61% with surface irrigation and from 81 to 97% with overhead sprinkler irrigation. Deep percolation below 1.8 m was 4 to 11% of applied surface irrigations and rain, but was undetectable in the overhead sprinkler. Leaching of NO3 was apparently the largest N loss pathway in the surface‐irrigated system. Fertigating UAN into surface irrigation resulted in similar lint yields and RE as knifing UAN. Use of Agrotain Plus with UAN gave similar yields and RE as using UAN alone. Reflectance‐based N management using normalized difference vegetation index‐amber (NDVIA) saved 50% of N fertilizer of the full soil‐test based dose without a yield reduction in three of four site‐ years. Nitrogen fertilizer was over‐prescribed with the soil‐test‐based treatment. This may have been due to not accounting for N mineralization, which the reflectance method indirectly measures.

Nitrogen Fertilizer Use Efficiency of Pepper as Affected by Irrigation and Fertilization Regime

The pepper producers in the Republic of Macedonia have used drip irrigation systems to increase yield in recent years, but more research is still needed, related to irrigation scheduling and precise requirement of nitrogen fertilizer to maximise pepper yield. Therefore, a two year experiment was conducted in a plastic house to determine the nitrogen fertilizer use efficiency (NFUE) and yield potential of pruned pepper as affected by irrigation and fertilization regime. Four experimental treatments were applied in this study. Three of the treatments were drip fertigated (DF1, DF2, DF3), while the fourth treatment was furrow irrigated with conventional fertilization (ØB). The labelled urea with 1% concentration of a stable isotope of nitrogen (15N) was applied for determination of NFUE. The results of this study clearly showed that increased NFUE and pepper yield depend on irrigation and fertilization regime. Namely, NFUE was significantly increased with the application of nitrogen fertilizer through drip irrigation system as compared to conventional fertilization with furrow irrigation. Also, drip fertigation frequency positively affects percentage increase of NFUE. Furthermore, our results showed that drip fertigation treatments resulted in significantly higher pepper yields in comparison to conventional fertilization. Also, drip fertigation frequency at four and two days (DF2 and DF1) resulted in higher yields when compared with drip fertigation scheduled by using tensiometers (DF3). Generally, to reach acceptable pepper yield with high NFUE, we recommend drip fertigation with a frequency of two to four days combined with two main shoots of pruned pepper in order to increase farmer’s income and to minimize the environmental impact.

Understanding the Fate of Applied Nitrogen in Pine Plantations of the Southeastern United States Using 15N Enriched Fertilizers

This study was conducted to determine the efficacy of using enhanced efficiency fertilizer (EEFs) products compared to urea to improve fertilizer nitrogen use efficiency (FNUE) in forest plantations. All fertilizer treatments were labeled with 15N (0.5 atom percent) and applied to 100 m2 circular plots at 12 loblolly pine stands (Pinus taeda L.) across the southeastern United States. Total fertilizer N recovery for fertilizer treatments was determined by sampling all primary ecosystem components and using a mass balance calculation. Significantly more fertilizer N was recovered for all EEFs compared to urea, but there were generally no differences among EEFs. The total fertilizer N ecosystem recovery ranged from 81.9% to 84.2% for EEFs compared to 65.2% for urea. The largest amount of fertilizer N recovered for all treatments was in the loblolly pine trees (EEFs: 38.5%–49.9%, urea: 34.8%) and soil (EEFs: 30.6%–38.8%, urea: 28.4%). This research indicates that a greater ecosystem fertilizer N recovery for EEFs compared to urea in southeastern pine plantations can potentially lead to increased FNUE in these systems.

Analysis of water and nitrogen use efficiency for maize (Zea mays L.) grown on soft rock and sand compound soil.

Maize was grown on compound soils constituted from mixtures of soft rock and sand at different ratios, and water use efficiency (WUE), nitrogen use efficiency (NUE) and fertilizer nitrogen use efficiency (FNUE) were quantified. The data were used to assist in designing strategies for optimizing water and nitrogen management practices for maize on the substrates used. Maize was sown in composite soil prepared at three ratios of soft rock and sand (1:1, 1:2 and 1:5 v/v) in Mu Us Sandy Land, Yuyang district, Yulin city, China. Yields, amount of drainage, nitrogen (N) leaching, WUE and NUE were calculated. Then a water and nitrogen management model (WNMM) was calibrated and validated. No significant difference in evapotranspiration of maize was found among compound soils with soft rock/sand ratios of 1:1, 1:2 and 1:5, while water drainage increased significantly with increasing soft rock/sand ratio. WUE increased to 1.30 kg m-3 in compound soil with 1:2 soft rock/sand ratio. Nitrogen leaching and ammonia volatilization were the main reason for nitrogen loss, and N reduction mainly relied on crop uptake. NUE and FNUE could reach 33.1 and 24.9 kg kg-1 N respectively. Water drainage and nitrogen leaching occurred mostly during heavy rainfall or irrigation. Through a scenario analysis of different rainfall types, water and fertilizer management systems were formulated each year. This study shows that soft rock plays a key role in improving the WUE, NUE and FNUE of maize. © 2016 Society of Chemical Industry.

Performance of partial root-zone drip irrigation for sugar beet production in a semi-arid area

Partial root-zone drying (PRD), a water-saving irrigation strategy, is being tested in many field crops species. In this study, the effects of PRD on root yield, sugar yield, water use efficiency (WUE), and fertilizer-nitrogen use efficiency (FNUE) of field-grown sugar beet were compared with those of conventional deficit irrigation (CDI) and full irrigation (FI). The experiments were conducted at Konya-Çumra, a Central Anatolian region of Turkey, in 2012 and 2013. Five irrigation techniques were designed and three nitrogen levels were chosen for the current study. These five irrigation techniques were applied to the study crops with the help of a drip irrigation system. In FI (control), the irrigation water was applied to both sides of the root system such that 35–40% of the available soil moisture was consumed in the 0.90-m root zone. In CDI50 and CDI75, 50% and 75% irrigation water of FI, respectively, was supplied to both sides of the root system. In alternative PRD50 (APRD50), the half of the root system was exposed to soil drying and the other half was kept well-watered with 50% irrigation water of FI. In fixed PRD50 (FPRD50), 50% irrigation water of FI was supplied only to half of the fixed side of the root system. Furthermore, the three chosen nitrogen levels included N100, where the plant’s nitrogen requirement is met completely; N75, where 25% reduction was made in the plant’s nitrogen requirement; and N50, where 50% reduction was made in the plant’s nitrogen requirement. Although the effect of nitrogen levels on sugar beet root and sugar yields was not significant, irrigation treatments had a significant effect (5% of the level). Compared to the FI treatment, the CDI75, CDI50, APRD50, and FPRD50 treatments decreased the standardized root and sugar yields by 6.36%, 26.97%, 19.12%, and 23.50%, respectively. APRD50 and FPRD50 increased the standardized yield by 10.74% and 4.75% compared to CDI50, respectively. In addition, when same amount of irrigation water was used, PRD (APRD50 and FPRD50) treatments outperformed CDI50 in WUE and FNUE of sugar beets. Compared to FI and CDI50, APRD50 increased WUEroot by 19.8% and 8.5% and FNUEroot by 26.2% and 68.2%, respectively. The varying nitrogen levels had a significant effect on FNUEroot and FNUEsugar. The highest FNUEroot and FNUEsugar values were obtained with N50. Further, combinations of different irrigation treatments and nitrogen levels had a significant effect on FNUEroot.

A critical re-evaluation of controls on spatial and seasonal variations in nitrate concentrations in river waters throughout the River Derwent catchment in North Yorkshire, UK.

Since mean nitrate concentration along single river channels increases significantly with percent arable land use upstream of sampling points and autumn/early winter flushes in nitrate concentration are widespread, it is generally concluded that farmers contribute most of the nitrate. For the River Derwent in North Yorkshire, the correlation between nitrate concentration and percent arable land use is much poorer when tributary data are included in the equation, because of greater variations in dilution by water draining upland areas and in other N input sources. For the whole river system therefore, percent upland moorland/rough grazing land cover is an appreciably better predictor than percent arable land use for nitrate concentration. Upland land use encompasses the higher precipitation and runoff in such areas, and the subsequent greater dilution downstream of both arable land runoff and effluent from treatment works, as well as an inverse correlation to percent arable land use. This is strongly supported by the observation that, for the Derwent, Meteorological Office rainfall data alone proved even better than percent moorland rough grazing for predicting nitrate concentration. The dilution effect is therefore substantial but highly seasonal; lower runoff and dilution in summer offset the lower leaching losses from arable land, and higher dilution and runoff in winter offset greater nitrate leaching losses from arable soils. Because of this, coupled to improved efficiency of nitrogen fertilizer use, seasonality trends in nitrate concentrations that were pronounced a decade ago now have all but disappeared in the catchment.

3,4-Dimethylpyrazole phosphate (DMPP) reduces activity of ammonia oxidizers without adverse effects on non-target soil microorganisms and functions

The nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is widely used within agriculture to reduce nitrate leaching and improve nitrogen use efficiency of fertilizers, but few studies examined effects on non-target soil functions and microorganisms, i.e. other than the intended delay of ammonia oxidation. We investigated effects of DMPP amendment equivalent to 0 (Control), 1 (regular dose, RD) or 10 (high dose, HD) kgha−1 in a sandy loam grassland soil at 50% water-filled pore space. Following incubation for 1, 7 or 14 d, soil was analyzed for fluorescein diacetate hydrolysis, dehydrogenase activity, phospholipid fatty acid composition and potential ammonia oxidation. DMPP showed no significant non-target effects (p>0.05), but a possible stress response in HD was indicated by a factor analysis of phospholipid fatty acid composition. There was a strong DMPP inhibition on potential ammonia oxidation which was still significant (p<0.05) in HD after 14 d. In separate treatments receiving 50mg NH4+-Nkg−1 dry soil in addition to DMPP, the inhibition of nitrate accumulation was similar in RD and HD at around 75%. Abundances of the gene amoA from ammonia oxidizing bacteria (AOB) and archaea (AOA) were quantified, and cell-specific nitrification rates were estimated. There was a general trend of increasing AOA and AOB abundance towards the end of incubation irrespective of DMPP treatment, whereas cell-specific activity of AOA and/or AOB was reduced in the presence of DMPP. Overall, this study indicated that DMPP effectively inhibited nitrification activity without effects on ammonia oxidizer populations, as well as non-target soil microorganisms or functions.

Net global warming potential and greenhouse gas intensity from the double rice system with integrated soil–crop system management: A three-year field study

The impact of integrated soil–crop system management (ISSM) on net global warming potential (GWP) and greenhouse gas intensity (GHGI) is poorly documented though crucial for food security and nitrogen fertilizer use efficiency (NUE). Using local farming practices (FP) and no nitrogen (NN) as the controls, three ISSM practices at different N rates were established in 2009 in a double rice system in Hunan Province, China. Soil organic carbon sequestration rates (SOCSR) were estimated by changes in SOC between 2009 and 2014. Field measurements of methane (CH4) and nitrous oxide (N2O) fluxes, grain yield and NUE of early and late rice were measured from April 2011 through April 2014. The net GWP of the annual CH4 and N2O emissions and SOCSR and the GHGI over the three years in the FP was 15.35 t CO2 eq ha−1 year−1 and 1.00 kg CO2 eq kg−1 grain. The ISSM (N2) treatment increased annual rice yield by 23%, NUE by 76% and SOCSR by 129%, with similar sizes of net GWP and GHGI under the same N input relative to the FP. A second ISSM (N1) treatment in which annual fertilizer N input was decreased by 20% also showed the potential to lower net GWP and GHGI and increase SOCSR and significantly increased annual rice grain yield by 8.6% and NUE by 59%. The third ISSM (N3) in which fertilizer N input was 20% greater than in FP, significantly increased annual rice yield by 26%, NUE by 57% and SOCSR by 98% but notably increased the CH4 and N2O emissions. Our findings show that the ISSM strategies are promising and feasible in sustainable rice agriculture for food security and GHGs mitigation.

Impact of Cultivation Practices in Oasis Agriculture on Soil Fertility Dynamics and the Relationship with Cotton Nitrogen-Use Efficiency in the Southern Rim of the Tarim Basin, Xinjiang, China

Twenty croplands in the Cele Oasis, at the southern margin of the Tarim Basin of Xinjiang, representing 100, 80, 30, 15, and 10 years of cultivation, were selected to investigate the relationship between soil fertility and nitrogen-fertilizer-use efficiency (NUE) of cotton and its changes over time. After long-term cultivation, significant increases were observed in soil organic matter (SOM) and total macronutrients. The key factors contributing towards the soil fertility index (SFI) were SOM, available potassium (AK), and phosphorus. The values of SFI declined in the following order: 80 (0.95) > 100 (0.68) > 30 (0.43) > 15 (0.41) > 0 (0.37) > 10 (0.34) years. No significant relationship was found between SFI and NUE. A significant correlation was observed among cotton yield, partial factor productivity from applied N, and AK. This indicates that the variation of AK content plays the most important role in soil fertility and cotton yield. Moderate K fertilization is recommended in the oasis croplands.

Impact of biochar application on nitrogen nutrition of rice, greenhouse-gas emissions and soil organic carbon dynamics in two paddy soils of China

Two field microcosm experiments and 15N labeling techniques were used to investigate the effects of biochar addition on rice N nutrition and GHG emissions in an Inceptisol and an Ultisol. Biochar N bioavailability and effect of biochar on fertilizer nitrogen-use efficiency (NUE) were studied by 15N-enriched wheat biochar (7.8803 atom% 15N) and fertilizer urea (5.0026 atom% 15N) (Experiment I). Corn biochar and corn stalks were applied at 12 Mg ha−1 to study their effects on GHG emissions (Experiment II). Biochar had no significant impact on rice production and less than 2 % of the biochar N was available to plants in the first season. Biochar addition increased soil C and N contents and decreased urea NUE. Seasonal cumulative CH4 emissions with biochar were similar to the controls, but significantly lower than the local practice of straw amendment. N2O emissions with biochar were similar to the control in the acidic Ultisol, but significantly higher in the slightly alkaline Inceptisol. Carbon-balance calculations found no major losses of biochar-C. Low bio-availability of biochar N did not make a significantly impact on rice production or N nutrition during the first year. Replacement of straw amendments with biochar could decrease CH4 emissions and increase SOC stocks.