Urea Application Rate Research Articles

Effects of liquid urea rates on nitrogen dynamics, growth, and yield of corn (Zea mays L.)

Arbitrary use of urea fertilizer reduces nitrogen use efficiency (NUE) and increases the risk of environmental pollution. An experiment was conducted at the Universiti Putra Malaysia from November 2019 to March 2020 to evaluate the application methods and rates of liquid urea (LU) on the yield performance of corn. The treatments were, U0 = control, GU100 = Granular urea (GU) 100%, LU100 = LU 100%, LU50 = LU 50% and LU33 = LU 33%, in two equal splits at 10th and 28th days after sowing (DAS) in randomized completely block design, replicates four. Results showed that plant height (206.99 cm, 216.92 cm, 214.61 cm), ear height (88.13 cm, 88.63 cm, 86.00 cm), days of maturity (88.75, 89.00, 86.75 days), number of grains per kernel row (32.25, 34.50, 33.75), fresh cob weight (10,886.60 kg ha−1, 10,946.60 kg ha−1, 10,927.93 kg ha−1) and 100-grain weight (20.51 g, 22.50 g, 21.39 g) of corn were not different significantly (p ≤ 0.05) in GU100, LU100 and LU50 treatments, respectively. The highest yield of corn was found with LU100 (6249.03 kg ha−1) treatment whereas the yield in LU50 (5666.50 kg ha−1) and GU100 (5746.64 kg ha−1) were not different significantly. Nitrogen (%) in plants was the highest in LU100 followed by LU50 treatment which was significantly higher than GU100 treatment. The total N content was also the highest in LU100 (102.83 kg ha−1) though the total N content was not different significantly in LU50 (77.62 kg ha−1) and GU100 (83.84 kg ha−1) treatments. The NUE was the highest in LU50 (66.92%) treatment followed by LU100 (51.47%) treatment. The results of the study suggested that LU was superior to GU and the LU100 was the best application rate while LU50 treatment was comparable to GU100 in corn cultivation.

Impact of biocrust on soil nitrogen maintenance and microbial composition in citrus orchards under varying urea application rates

Biocrust communities and their effects on soil nitrogen (N) content in natural drylands have been extensively studied. However, their significance in citrus orchards, which are typically managed with N fertilizer, remains unclear. To address this, an investigation was conducted in a citrus orchard subjected to varying levels of urea application (0 %, 70 %, and 100 % of the local N fertilizer application) over three years. The study focused on biocrust communities dominated by bryophytes, examining their community and individual characteristics, and comparing the properties and microbial communities of soils with and without biocrust cover. The results showed that biocrust had the highest percent coverage (56.1 %) in the plot with 70 % local N fertilizer application. Dicranella heteromalla was the dominant biocrust species across all treatments, exhibiting greener and longer leaves with 70 % local N fertilizer application. Biocrust cover significantly (P < 0.01) influenced soil total nitrogen content, soil water content, soil total carbon content, and soil dissolved organic carbon content. In contrast, fertilizer application had non-significant effects on the physicochemical properties of soils, regardless of biocrust cover. A notable difference in bacterial phyla composition was observed between soils with and without biocrust cover (PERMANOVA, P = 0.001), although fertilization did not significantly affect the bacterial diversity index. Additionally, biocrust cover significantly (P < 0.01) influenced predicted soil bacterial functional groups, including ureolysis and nitrogen fixation, while fertilizer application had a weaker impact on these bacterial functional groups. In conclusion, nitrogen application altered the community and dominant species characteristics of biocrust but did not overshadow the effects of biocrust on soil N dynamics. In the citrus orchard with varying levels of urea application, biocrust played a crucial role in soil water retention, N maintenance, and predicted microbial ecological functions related to N cycling.

Influence of soil organic matter, fertiliser formulation and season on fertiliser nitrogen use efficiency in temperate pastures

Intensively grazed dairy systems use high inputs of fertiliser nitrogen (N), and often supplementary irrigation, to ensure adequate pasture production to support milk output and meet the growing food demand. However, the efficiency of N use in these systems can be low and potential environmental impacts high. This study aimed to test the hypothesis that (1) use of two inhibitors, the urease inhibitor N-(n-butyl) thiophosphorictriamide (NBTPT) and the nitrification inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) reduced N loss and improved pasture production compared to conventional N fertiliser (urea) in irrigated temperate perennial ryegrass (Lolium perenne L.) dairy pasture, and (2) their efficiency was affected by soil and environmental parameters. The effect of repeated applications of urea, at different rates, and the inhibitors were studied on pasture production and agronomic apparent fertiliser N use efficiency (NUE) over 2.5 years. The fate of a single application of N was determined through recovery of 15N-labeled fertiliser applied at 20 and 40 kg N ha−1 was studied in the field for one year. The highest yield and NUE occurred in spring–summer (from August to February) reflecting optimal growing conditions. The highest NUE occurred at low rates of urea application (20 and 40 kg N ha−1). Mineralisation played a key role in supplying N to pasture with 64–82% of total plant N derived from soil organic matter (SOM). Less than 50% of the applied N was recovered in the pasture (37–43%) with a large component retained in the soil (26–43% after one year, 0–40 cm), and slowly released in small amounts (< 2%) to the pasture over time, highlighting the abundant capacity of the native soil N pool to supply pasture N. Loss of N fertiliser (14–31%) was attributed to primarily ammonia (NH3) volatilisation and nitrate (NO3−) leaching. Use of the inhibitors NBTPT and DMPP did not significantly affect pasture yield or NUE, most likely because fertiliser N saved with the inhibitors only played a minor role in plant nutrition with the majority of the plant nutrition provided by the soil organic matter pool.

Linkages of soil and microbial stoichiometry to crop nitrogen use efficiency: Evidence from a long-term nitrogen addition experiment

Increasing crop nitrogen use efficiency (NUE) has important implications for food security and agricultural sustainability. Changes in nutrient availability due to stoichiometric imbalances in soil under long-term application of nitrogen (N) can limit crop NUE and yield. However, little is known about the linkages across stoichiometric balance, N fertilizer application, and N uptake. We investigated the changes in soil stoichiometry, microbial community, and crop NUE relative to N fertilizer application in a 16-year field experiment in which five levels (0, 70, 140, 210 and 280 kg N ha−1) of mineral N fertilizer treatment were applied to wheat and maize cropland. The results showed that the P storage decreased from 4.3 Mg P ha–1 under the fertilizer dose of 0 kg N ha−1 to 3.5 Mg P ha–1 under the fertilizer dose of 280 kg N ha−1. Thus, long-term N application increased soil C/P and N/P ratios, in a marked decrease in the content of soil available P. The microbial community based on phospholipid fatty acids (PLFAs) increased with increasing N addition rates, from 0 to 140 kg N ha−1, but significantly decreased at application rates above 210 kg N ha−1. Thus, applying N at a rate of 140 kg ha−1 resulted in the N threshold rate for microorganism survival being reached or exceeded. The crop NUE peak occurred at the urea application rate of 140 kg N ha−1 (60.4 %), after which NUE declined. The soil elementary and enzymatic stoichiometric ratios under long-term N addition directly affected crop NUE in the topsoil. Soil elementary stoichiometric ratios affected crop NUE by indirectly altering microbial biomass of the subsoil. Overall, soil stoichiometric imbalances under long-term N addition were the key factors driving NUE across N gradients.

Non-native Brachiaria humidicola with biological nitrification inhibition capacity stimulates in situ grassland N2O emissions.

Brachiaria humidicola, a tropical grass, could release root exudates with biological nitrification inhibition (BNI) capacity and reduce soil nitrous oxide (N2O) emissions from grasslands. However, evidence of the reduction effect in situ in tropical grasslands in China is lacking. To evaluate the potential effects of B. humidicola on soil N2O emissions, a 2-year (2015-2017) field experiment was established in a Latosol and included eight treatments, consisting of two pastures, non-native B. humidicola and a native grass, Eremochloa ophiuroide, with four nitrogen (N) application rates. The annual urea application rates were 0, 150, 300, and 450 kg N ha-1. The average 2-year E. ophiuroides biomass with and without N fertilization were 9.07-11.45 and 7.34 t ha-1, respectively, and corresponding values for B. humidicola increased to 31.97-39.07 and 29.54 t ha-1, respectively. The N-use efficiencies under E. ophiuroide and B. humidicola cultivation were 9.3-12.0 and 35.5-39.4%, respectively. Annual N2O emissions in the E. ophiuroides and B. humidicola fields were 1.37 and 2.83 kg N2O-N ha-1, respectively, under no N fertilization, and 1.54-3.46 and 4.30-7.19 kg N2O-N ha-1, respectively, under N fertilization. According to the results, B. humidicola cultivation increased soil N2O emissions, especially under N fertilization. This is because B. humidicola exhibited the more effective stimulation effect on N2O production via denitrification primarily due to increased soil organic carbon and exudates than the inhibition effect on N2O production via autotrophic nitrification. Annual yield-scaled N2O emissions in the B. humidicola treatment were 93.02-183.12 mg N2O-N kg-1 biomass, which were significantly lower than those in the E. ophiuroides treatment. Overall, our results suggest that cultivation of the non-native grass, B. humidicola with BNI capacity, increased soil N2O emissions, while decreasing yield-scaled N2O emissions, when compared with native grass cultivation.

Performance evaluation of an electronically controlled tractor-operated applicator for liquid urea application

Currently, granular urea (most commonly used fertilizer) is applied through broadcasting by farmers in the field. Granular urea causes significant losses due to slower soil mineralization rates, as well as ammonia volatilization and immobilization. Hence, fertilizing crops is becoming an increasingly difficult task due to low use efficiency and in mulch field conditions, it becomes more severe. The research done on mechatronic systems of applying liquid fertilizer by spot injection in field is limited. In the present study, the performance of the developed tractor operated liquid urea applicator consisting of electronic metering mechanism was evaluated at the Research Farm of Punjab Agricultural University, Ludhiana, Punjab during 2020–22. Research was done at two different types of soil (S1: sandy loam, and S2: loam) for three different forward speeds (3.6, 2.7, 1.8 km/h). Results obtained from experiments indicated that both soil type and forward speed had a significant (P&lt;0.05) effect on the application rate of liquid urea. The best results were obtained without affecting crop yield at a forward speed of the machine 2.7 km/h with the application rate of 1090.85 litre/ha and 1035.18 litre/ha, fuel consumption 4.13 litre/h and 4.02 litre/h and crop yield 39.50 q/ha and 39.63 q/ha, for soil type S1 and S2 respectively. The cost of operation of machine was found 1996.53 `/ha. Developed tractor operated liquid urea applicator would help in improving conventional practices which are not aligned with environmental protection (e.g. gaseous emissions and nutrient losses) and boost the adoption rate of mechanized fertigation in the crops.

Zeolite Oil Palm Compost-Based Organomineral Fertilizer for Shallot Agronomic Performances and N Substitution

Application of organomineral fertilizer (OMF), which is the product of the inclusion of zeolite and palm oil compost in urea needs to be studied to determine its appropriate dose for the growth and yield of shallots and N substitution. This pot experiment was conducted from October to December 2020 at the Teaching and Research Field of Agriculture Faculty and consisted of five treatments arranged in a completely randomized design with five replications. The treatments were (1) 1.0 g urea, (2) 0.5 g urea + 1.15 g OMF, (3) 0.5 g urea + 2.30 g OMF, (4) 0.5 g urea + 3.45 g OMF, and (5) 0.5 g urea + 4.60 g OMF. The results showed that combined application of 0.5 g urea + 4.60 g OMF produced the highest values of plant height (30.60 cm), number of leaves (30.90), fresh weight of tubers per clump (30.90 g), dry tuber weight per clump (24.3 g), and tuber diameter (16.25 mm). The incorporation of zeolite and palm oil compost in urea reduced the application rate of urea up to 50% without reducing the growth and yield of shallot. Thus, N fertilizer use can be enhanced if urea is co-applied with zeolite and palm oil compost.

DMPP and Polymer-Coated Urea Promoted Growth and Increased Yield of Greenhouse Tomatoes

Improvements in nitrogen (N) use efficiency reduce stress on the environment and improve tomato production. A two-year trial was conducted in greenhouse tomatoes with a split-plot design, in which one factor was the N application rate (150 kg·ha−1, N1; 200 kg·ha−1, N2; and 250 kg·ha−1, N3) and two other factors were the type of urea applied (urea, T1; slow-release (polymer-coated) urea, T2, and nitrification inhibitors (3,4-dimethylpyrazole phosphate, DMPP) + urea, T3); no N fertilizer was applied in the control. The effects of the nitrogen (N) application rate and type of urea applied on the root morphology indexes, growth indexes, photosynthetic parameters, yield (Y), water use efficiency (WUE), and nitrogen agronomic efficiency (NAE) of greenhouse tomatoes were investigated. The results show that an appropriate N application rate (200 kg·ha−1) can improve tomato growth and net photosynthetic rate (Pn). With T3, the Y and WUE of greenhouse tomatoes first increased and then decreased as the N application rate increased, but with T1 and T2, the Y and WUE increased as the N application rate increased. The NAE of greenhouse tomatoes was significantly lower with N3 than with N2. The root growth, plant growth, Pn, Y, WUE, and NAE of the tomatoes were improved with T2 and T3 compared to T1. These findings can be used to promote N conservation and increase the Y of facility agriculture crops.

Modeling ammonia volatilization following urea and controlled-release urea application to paddy fields

• The WHCNS model performed well in simulating NH 3 flux measured by a continuous ventilation method. • Urea split application reduced the peak of NH 3 flux but increased total NH 3 loss. • Controlled-release urea application significantly reduced NH 3 loss compared to urea. • The controlled-release urea rate was recommended to reduce N loss without reducing yield. Ammonia volatilization, a main pathway of nitrogen (N) loss in paddy fields, can easily lead to environmental problems, such as haze and water eutrophication. Field measurement of ammonia volatilization is time-consuming and expensive. Soil–crop system models can simulate the effect of different fertilizer management practices on NH 3 volatilization and compensate for the limitations of field measurement. Therefore, the WHCNS (soil Water Heat Carbon Nitrogen Simulator) model was used to evaluate the feasibility of simulating NH 3 volatilization in paddy fields under different N fertilizer types and application methods. The field experiment, including four treatments of farmer’s practice (FP), basal application of urea in one dose (SBN), split application of urea in three doses (SPN), and basal application of controlled-release urea in one dose (CRU), was conducted from 2013 to 2014. All treatments were conducted with a fertilizer rate of 165 kg N ha −1 , except for FP with a rate of 210 kg N ha −1 . The measured dry matter weight, grain yield, N uptake, and NH 3 flux were used to test the WHCNS model. The model evaluation indices of Nash–Sutcliffe efficiency ( NSE ) and index of agreement ( d ) were close to 1 for the measured variables, except for NSE of yield (0.16). The normalized root mean square error ( NRMSE ) of NH 3 flux was slightly over 30%, but lower than 30% for the other items. Results showed that the model can successfully simulate rice yield and NH 3 flux of urea and controlled-release urea under different application methods. The simulated annual average cumulative NH 3 losses of FP, SBN, SPN, and CRU accounted for 18.9%, 17.8%, 20.6%, and 10.1% of their N inputs, respectively. Compared with the FP treatment, the ratios of NH 3 losses of the SBN and CRU treatments were decreased by 1.2%-8.8%. Compared with the SBN treatment (the same rate of 165 kg N ha −1 ), SPN reduced the peak of NH 3 flux but increased the cumulated NH 3 losses and CRU significantly reduced the NH 3 flux and cumulative NH 3 losses. The application rate of controlled-release urea could be further optimized by refined model calculations to reduce NH 3 volatilization and total N loss while maintaining yield.

Response of Leaf Senescence, Photosynthetic Characteristics, and Yield of Summer Maize to Controlled-Release Urea-Based Application Depth

To explore the response of summer maize leaf senescence, photosynthetic characteristics, and yield to the depth of one-time base application of controlled-release urea, which provides a theoretical basis for the light and simplified production of summer maize. Seven treatments were set up with Zhengdan 958 as the material under field conditions, including no nitrogen fertilizer (CK), surface spreading (DP0), furrow application depth of 5 cm (DP5), 10 cm (DP10), 15 cm (DP15), 20 cm (DP20), 25 cm (DP25). The results showed that under the same nitrogen application rate, there are significant differences in the effects of summer maize leaf senescence and photosynthetic characteristics with the increase of fertilization depth, and DP10 and DP15 have the best effects. The LAI of DP10 and DP15 increased by 5.1% and 5.5% compared to DP0 at tasseling stage, and chlorophyll content increased by 6.8% and 7.3% in 10 days after tasseling. Compared with DP0, superoxide dismutase (SOD) increased by 13.1% and 10.5%, the content of soluble protein increased significantly, while the content of malondialdehyde (MDA) decreased by 9.8% and 10.8%, respectively. In addition, Pn and Gs of the ear-leaf significantly increased by 13.9%, 16.5%, and 26.1% and 31.9% at tasseling stage, respectively, over DP0, while Ci decreased by 22.3% and 26.4%, respectively; meanwhile, the photochemical quenching (qP) and quantum yield (ΦPSII) of the reaction center of photosystem II (PSII) of the ear-leaf were significantly improved, the non-photochemical quenching (NPQ) was significantly reduced. The yield of DP10 and DP15 heightened significantly; two-year average value increased by 5.7% and 6.0% compared with DP0; the kernels per spike and 1000-kernels weight increased by 4.8%, 5.2%, and 4.1%, 5.2%, respectively. Comprehensive analysis of LAI, chlorophyll content, various protective enzyme activities and MDA, soluble protein content showed that 10–15 cm is the appropriate fertilization depth when the nitrogen application rate of controlled-release urea is 225 kg N per hectare. In consequence, optimizing fertilization depth of controlled-release urea as a simplified fertilization mode could improve the nitrogen utilization efficiency and obtain higher yield in summer maize, which provides technical support for large-scale application of controlled-release urea.

Isotopic assessment of soil N2O emission from a sub-tropical agricultural soil under varying N-inputs

Nitrogen fertilizers result in high crop productivity but also enhance the emission of N2O, an environmentally harmful greenhouse gas. Only approximately a half of the applied nitrogen is utilized by crops and the rest is either vaporized, leached, or lost as NO, N2O and N2 via soil microbial activity. Thus, improving the nitrogen use efficiency of cropping systems has become a global concern. Factors such as types and rates of fertilizer application, soil texture, moisture level, pH, and microbial activity/diversity play important roles in N2O production. Here, we report the results of N2O production from a set of chamber experiments on an acidic sandy-loam agricultural soil under varying levels of an inorganic N-fertilizer, urea. Stable isotope technique was employed to determine the effect of increasing N-fertilizer levels on N2O emissions and identify the microbial processes involved in fertilizer N-transformation that give rise to N2O. We monitored the isotopic changes in both substrate (ammonium and nitrate) and the product N2O during the entire course of the incubation experiments. Peak N2O emissions of 122 ± 98 μg N2O-N m−2 h−1, 338 ± 49 μg N2O-N m−2 h−1 and 739 ± 296 μg N2O-N m−2 h−1 were observed for urea application rate of 40, 80, and 120 μg N g−1. The duration of emissions also increased with urea levels. The concentration and isotopic compositions of the substrates and product showed time-bound variation. Combining the observations of isotopic effects in δ15N, δ18O, and 15N site preference, we inferred co-occurrence of several microbial N2O production pathways with nitrification and/or fungal denitrification as the dominant processes responsible for N2O emissions. Besides this, dominant signatures of bacterial denitrification were observed in a second N2O emission pulse in intermediate urea-N levels. Signature of N2O consumption by reduction could be traced during declining emissions in treatment with high urea level.

Rapid Detection of Urea Fertilizer Effects on VOC Emissions from Cucumber Fruits Using a MOS E-Nose Sensor Array

The widespread use of nitrogen chemical fertilizers in modern agricultural practices has raised concerns over hazardous accumulations of nitrogen-based compounds in crop foods and in agricultural soils due to nitrogen overfertilization. Many vegetables accumulate and retain large amounts of nitrites and nitrates due to repeated nitrogen applications or excess use of nitrogen fertilizers. Consequently, the consumption of high-nitrate crop foods may cause health risks to humans. The effects of varying urea–nitrogen fertilizer application rates on VOC emissions from cucumber fruits were investigated using an experimental MOS electronic-nose (e-nose) device based on differences in sensor-array responses to volatile emissions from fruits, recorded following different urea fertilizer treatments. Urea fertilizer was applied to cucumber plants at treatment rates equivalent to 0, 100, 200, 300, and 400 kg/ha. Cucumber fruits were then harvested twice, 4 and 5 months after seed planting, and evaluated for VOC emissions using an e-nose technology to assess differences in smellprint signatures associated with different urea application rates. The electrical signals from the e-nose sensor array data outputs were subjected to four aroma classification methods, including: linear and quadratic discriminant analysis (LDA-QDA), support vector machines (SVM), and artificial neural networks (ANN). The results suggest that combining the MOS e-nose technology with QDA is a promising method for rapidly monitoring urea fertilizer application rates applied to cucumber plants based on changes in VOC emissions from cucumber fruits. This new monitoring tool could be useful in adjusting future urea fertilizer application rates to help prevent nitrogen overfertilization.

Urea Application Rate for Crop Straw Decomposition in Temperate China

Returning straw to the field has become the most important straw utilization method in China. The aim of this research was to study the appropriate amount of nitrogen fertilizer applied when returning the straw of three major crops (wheat, rice, and corn) to the field in areas under low to high yield levels based on the demand of nitrogen for microbial decomposition of straw. Under the condition of returning 100% straw to the field, we developed the formula for calculating the nitrogen application rate and estimated the urea application rate for the three major grain crops. The results showed that returning straws of wheat, early-season rice, middle-season rice and late-season rice, and corn to the field with urea application at the rate of about 150 kg/ha, 120～135 kg/ha, 75 kg/ha, and 75～90 kg/ha, respectively, can provide sufficient nitrogen for microbial decomposition. The urea application rate for returning 100% wheat straw to the field in Huang-Huai-Hai region, Middle-Lower Yangtze region, Loess plateau region, and Northwest arid region was 135–230 kg/ha, 110–190 kg/ha, 85–145 kg/ha, and 95–165 kg/ha, respectively. 52.5–98.5 kg/ha of urea was used for 100% early rice straw returning to the field in Middle-Lower Yangtze region and South China. In addition, the urea application rate for 100% middle-late rice straw returning to the field was 95–180 kg/ha, 100–185 kg/ha, 95–175 kg/ha, and 75–140 kg/ha, respectively. The rate of urea application for 100% corn straw returning to the field in Northeast China, Huang-Huai-Hai, Northwest arid region, and Southwest China was 60–135 kg/ha, 50–115 kg/ha, 60–135 kg/ha, and 45–105 kg/ha, respectively. The amount of nitrogen fertilizer required for the total return of crop straw is not only affected by crop straw C : N, yield per unit area, and ratio of grass to grain but also affected by straw returning mode, regional nitrogen application level, and other factors. Therefore, the amount of nitrogen fertilizer should be adjusted according to the type of cropping system, soil, and climatic conditions of the specific location. This substantial N input for stimulating straw decomposition may favor N losses with nitrate leaching and nitrous oxide emissions and hold a potential for soil N eutrophication in the long term if the level is not carefully adjusted to the N requirement of the subsequent crops and changes in soil organic matter levels.

Phosphorus mineralization affected by urea in an intensively managed agricultural soil

AbstractA mineralizable P fractionin soils has not been considered in the current agronomic soil P test. Organic P might be a potential source of bioavailable P under the influence of specific soil conditions such as N input. In this laboratory incubation study, the effects of urea (0.1–0.3 g N kg–1 soil) on P mineralization was investigated in an intensively managed agricultural soil using chemical extractions, phosphatase activity analysis, and solution 31P nuclear magnetic resonance spectroscopy (NMR). All urea application rates stimulated P release and P mineralization after 5 d, and bioavailable P increased for up to 40 d. The result of NMR analysis and phosphatase activity supported a shift from organic P to orthophosphate. Urea applications generally increased labile P from ∼5 to ∼24 μg g–1. However, acidity generated from the oxidation of NH4+ under the highest urea treatment (0.3 g of N kg–1 soil) suppressed P mineralization, indicating the degree of urea application rate is sensitive to P mineralization. The results suggested the use of urea could enhance P bioavailability in P‐rich agricultural soils. Tapping into reusable organic P resources in soils might be one of the practical and conservative approaches in the current agriculture.

Calibration and Performance Evaluation of Grain Corn Fertilizing Implement

Fertilisation in grain corn production is an important stage that must be done properly in terms of the amount of fertiliser used to reduce wastage and ensure crop growth. A fertilising implement brand Gasprado, was calibrated and evaluated for its performance to apply urea to grain corn crops at MARDI Seberang Perai, Pulau Pinang. Calibration was conducted to set the right metering for the device's opening to drop urea that meets the application rate of 130kg/ha. This was done by measuring the amount of urea dropped for a particular setting and distance. The machine has four metering devices which were labelled as MD1, MD2, MD3 and MD4. Additionally, the fertiliser applicator also comes with spring tine cultivating devices. The implement was tested for fertilising 56 rows of grain corn in the distance of 62 m long. The times taken for the tractor to finish four rows per run along the 62-m distance and to turn at the headland were recorded to evaluate the performance. The implement's metering devices MD1, MD2, MD3 and MD4 were calibrated at setting scales of B-1.5, B-0, B-0 and B-0, respectively that gave the urea application rate of 133 kg/ha, which was the nearest rate to the recommendation. The average working speed of the operation was at 4.08 km/h with the theoretical field capacity to be at 1.224 ha/h. Meanwhile, the machine's effective field capacity was 0.5208 ha/h, which had a field efficiency of 42.5 % for the particular farm design. The use of machine can speed up the operation of applying fertiliser to the grain corn crop but the performance is dependent on the farm layout.

Concomitant tracking of NH3, N2O and soil mineral-N using steady-state incubation cells to enhance sustainability of urea fertilization approaches

Enhancing nitrogen use efficiency to assure sustainable intensification of crop production, while minimizing N-environmental threats, is a major challenge. These drive important developments of N-fertilization approaches and enhanced efficiency N-fertilizers (EENFs). The complexity of N-dynamics under different soils, environmental conditions, and application modes requires improvement of decision-making tools. Meta-analyses demonstrate the contribution of EENFs to sustainable intensification. Yet, improvements based on local field specific information, and particularly with new N-fertilization approaches, are needed. This project focuses on an upgraded laboratory designed steady state incubation system connected to a Long-Path gas cell mounted on an FTIR spectrometer, allowing fast determination of NH3 and N2O emissions concomitant with mineral N-dynamics in soils under different N-fertilization approaches. The system was tested with four representative soils, fertilized with surface applied urea or urea amended with urease inhibitors (UI). Different soil water saturation (WS) levels and urea application rates were tested over 14 days of incubation·NH3 losses (%N-applied) in the steady state system were 2 to 7 times higher than in the previously designed non-steady state system. Highest losses were observed when urea was applied to lighter soils with pH above 7.5 (~13% to 46%), especially under low (30%) water saturation (WS). Substituting to UI reduced the accumulated NH3 losses (14 days) by 55 to 92%. Highest N2O losses were obtained with the lighter soils (1.2% to 1.7%) at 50% WS and lowest urea application rate. UI assisted in reducing N2O losses in some of the tested soils, showing different dependencies on WS and urea concentration. This variety demonstrates the complexity of the N-processes involved under different soils and conditions, and was also expressed in the mineral-N concentrations. This simple experimental design has the potential to improve our insights and help evaluate EENFs sustainability.

Reduced application and different combined applications of loss-control urea on summer maize yield and fertilizer efficiency improvement

<p id="C3">Loss-control urea with nanometer mineral loss control agent added during production period could reduce the loss of nitrogen (N) through adsorption. Figuring out the application rate of loss-control urea and the appropriate rate with conventional urea could provide evidences for summer maize one-time fertilization, N fertilizer reduction, and use efficiency improvement. Under different yield level soil conditions, field experiment was arranged to investigate the effects of different N fertilizer managements on summer maize yield, aboveground biomass, nutrient accumulation, photosynthetic characteristic, and N utilization efficiency. Treatments of conventional urea (N at 210 kg hm^-2), loss-control urea (full dose with N at 210 kg hm^-2, 10% reduction with N at 189 kg hm^-2, and 20% reduction with N at 168 kg hm^-2), and different combined proportions of loss-control urea and conventional urea (at 7:3, 5:5, and 3:7) were carried out. The results revealed that N fertilizer application could significantly increase the yield of summer maize and the full-dose loss-control urea treatments increased the yield by 22.96%-27.55%, compared with that under conventional urea application at high- and middle-yield soil conditions. The application of loss-control urea at 10% and 20% reduction sustained the summer maize yield at high- and middle-yield soil condition with improved grains per ear, compared with full-dose loss-control urea application. The N fertilizer utilization efficiency under loss-control urea at 20% reduction treatment at high-yield soil condition reached 41.60%. N accumulation was comparable with full-dose loss-control urea application under proportions of loss-control urea and conventional urea at 7:3 application. Meanwhile, this treatment could sustain the yield and straw biomass at high- and middle-yield level soil and significantly increased the yield and straw biomass at low-yield field. In conclusion, one-time application of loss-control urea with N at 210 kg hm^-2 could significantly improve the yield of summer maize and N efficiency of the fertilizer utilization. The application of loss-control urea with 20% reduction could sustain the summer maize yield with significantly improved N utilization efficiency at high- and middle-yield soil conditions, which was the suitable N fertilizer application for high- and middle-yield field. Loss-control urea and conventional urea at 7:3 application was suitable for N fertilizer application for low-yield field.

Temporal response of ureolytic and ammonia-oxidizing microbes and pasture yield to urea and NBPT at Leigh Creek of Victoria in Australia

The urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) has been reported to effectively reduce nitrogen (N) losses by inhibiting urea hydrolysis. However, the effect of NBPT on soil ureolytic and ammonia-oxidizing microbes is not well understood, with inconsistent effects on crop yield and nitrogen use efficiency (NUE). Further, repeated use or overuse of chemical fertilizers can have environmental implications like soil acidification. A field experiment was conducted at Leigh Creek, Victoria at a site with a history of repeated application of urea alone (40U) or with NBPT (as Green Urea NV® (40GU)) at 40 kg N ha−1, and urea applied at 80 kg N ha−1 (80U), to perennial ryegrass (Lolium perenne L.). We aimed to investigate the temporal effects of NBPT applied with urea on ureolytic and ammonia-oxidizing microbes, pasture dry matter (DM) yield, and NUE within a season following treatment applications. The abundance of ureolytic microbes was higher in the control (CK) compared to all N treatments on all sampling days. The ureC gene copy numbers in 40 GU were significantly lower than in 40U on sampling days seven and 45. There was no significant effect of NBPT on the abundance of ammonia oxidizers, but increasing urea application rate to 80 kg N ha−1 (80U) significantly increased the abundance of ammonia-oxidizing bacteria (AOB) on days 7 and 45, and complete ammonia oxidizers (comammox Nitrospira) clade B on day 7 compared to 40U. There was no significant effect of NBPT on pasture DM yield, N-uptake, or NUE. Increasing N application rate significantly increased pasture DM yield and N- uptake but this did not influence the pasture NUE.

Replacing nitrogen fertilizer with nitrogen-fixing cyanobacteria reduced nitrogen leaching in red soil paddy fields

Excessive chemical nitrogen (N) fertilizer application and flood irrigation in rice production can lead to substantial soil-N losses and low nitrogen-use-efficiency (NUE) in rice due to N leaching from red paddy soils. Although inoculation of irrigated fields with nitrogen-fixing cyanobacteria (NFC) has been shown to increase rice yield, there are few studies on N leaching and NUE in response to NFC when used in place of urea. A two-year field experiment was carried out to examine the concentrations of ammonium-N (NH4+-N), nitrate-N (NO3−-N), total dissolved N (TDN) and dissolved organic N (DON) in percolated irrigation water, as well as cumulative leaching losses after NFC was used to replace different application rates of urea in double cropped rice grown in red paddy soil. Four treatments were established: 1) CK, the control with no application of urea or NFC; 2) N10C0, a conventional full application of urea only; 3) N5C5, addition of a half-application of NFC to replace half of the conventional application rate of urea (N5C5); and 4) N0C10, a full application of NFC only. In 2017 and 2018, although the average rice yield of N0C10 was 25.0 % higher than that of CK, it was 23.8 % lower than that of N10C0. The average NUE of N10C0 was 34.7 %, and the average TDN leaching loss was 13.9 kg ha-1 per crop each year. Correspondingly, NUE of N5C5 was 47.7 %, which was 37.5 % higher than that of N10C0. Replacing 50 % of urea with NFC did not significantly decrease rice yield, but it reduced TDN leaching by 37.2 %. The results showed that the conventional way of fertilization caused the most N loss, while replacing partial urea with NFC significantly reduced the leaching losses of NH4+-N, NO3−-N and DON. Moreover, replacing 50 % of urea with NFC can retain more soil N than conventional fertilization at the end of the rice season because NFC can intercept, fix and delay release of N. Thus, the multiple functions of NFC in N cycling dynamics are more conducive to the retention of N by soil and greatly reduces N leaching.

Foliar Urea Applications Increase Yeast Assimilable Nitrogen Concentration and Alcoholic Fermentation Rate in ‘Red Spy’ Apples Used for Cider Production

Yeast assimilable nitrogen (YAN) can be a limiting nutritional factor for Saccharomyces cerevisiae yeast when fermenting apple (Malus ×domestica Borkh.) juice into hard cider. Endogenous YAN concentrations in apples are often below the recommended thresholds to completely use all of the fermentable sugar and minimize the production of off-flavors, such as hydrogen sulfide. Cider producers supplement apple juice with exogenous nitrogen to increase YAN. Urea, commonly applied to apple orchards to increase fruit size and yields, was tested for its ability to increase endogenous apple juice YAN. Starting 6 weeks before harvest in 2017 and 2018, a 1% urea solution was applied to ‘Red Spy’ apple trees one, three, or five times to create low-, medium-, and high-rate treatments, respectively. Relative to the control, the high treatment increased YAN by 229% in 2017 and by 408% in 2018. More than 90% of the YAN in all juice samples was composed of primary amino nitrogen (PAN). Among all treatments, PAN mostly comprised asparagine, and as urea applications increased, the relative concentration of asparagine also increased. Aspartic acid and then glutamic acid were the second and third most abundant amino acids in all treatments, respectively, but comprised less of the total PAN as the number of urea applications increased. Soluble solid concentration, pH, titratable acidity, and total polyphenol concentration were not different among treatments. There was a positive correlation between increased urea application rate and the maximum fermentation rate, which resulted in a shorter fermentation duration. Increasing the number of urea applications was also correlated with greater hydrogen sulfide (H2S) production in juice fermented from fruit harvested in 2017 but not for fruit harvested in 2018. No residual H2S was found in the finished cider from any treatment. Increasing the number of urea applications was estimated to be less expensive than supplementing the juice with Fermaid O™. There would have been no cost savings if Fermaid K™ was used as an exogenous nitrogen source. Foliar urea applications were estimated to be more expensive than supplementing juice with diammonium phosphate. This study demonstrated that foliar urea applications can effectively increase YAN concentration in cider apples while not negatively affecting other juice quality attributes.