Controlled-release Urea Treatments Research Articles

Controlled‐release urea decreased ammonia volatilization and increased nitrogen use efficiency of cotton

AbstractExcessive nitrogen (N) fertilizer input leads to higher N loss via ammonia (NH3) volatilization. Controlled‐release urea (CRU) was expected to reduce emission losses of N. An incubation and a plant growth experiment with Gossypium hirsutum L. were conducted with urea and CRU (a fertilizer mixture of polymer‐coating sulfur‐coated urea and polymer‐coated urea with N ratios of 5 : 5) under six levels of N fertilization rates, which were 0% (0 mg N kg−1 soil), 50% (110 mg N kg−1 soil), 75% (165 mg N kg−1 soil), 100% (220 mg N kg−1 soil), 125% (275 mg N kg−1 soil), and 150% (330 mg N kg−1 soil) of the recommended N fertilizer rate. For each type of N fertilizer, the NH3 volatilization, cotton yield, and N uptake increased with the rate of N application, while N use efficiency reached a threshold and decreased when N application rates of urea and CRU exceeded 238.7 and 209.3 mg N kg−1 soil, respectively. Ammonia volatilization was reduced by 65–105% with CRU in comparison to urea treatments. The N release characteristic of CRU corresponded well to the N requirements of cotton growth. Soil inorganic N contents, leaf SPAD values, and net photosynthetic rates were increased by CRU application, particularly from the full bloom stage to the initial boll‐opening stage. As a result, CRU treatments achieved significantly higher lint yield by 7–30%, and the N use efficiency of CRU treatments was increased by 25–124% relative to that of urea treatments. These results suggest that the application of CRU could be widely used for cotton production with higher N use efficiency and lower NH3 volatilization.

Comparative effects of nitrogen application on growth and nitrogen use in a winter wheat/summer maize rotation system

The application of fertilizer in agricultural production has become universally common for achieving high crop yields and economic benefits, but it has potential impacts on food safety, energy crisis and environmental pollution. Optimal management of fertilization is thus necessary for maintaining sustainable agriculture. Two-year (2013–2015) field experiment was conducted, in Yangling (108°24′E, 34°20′N, and 521 m a.s.l.), Shaanxi Province, China, to explore the effects of different nitrogen (N) applications on biomass accumulation, crop N uptake, nitrate N (NO3−-N) distribution, yield, and N use with a winter wheat/summer maize rotation system. The N applications consisted of conventional urea (U) (at 80 (U80), 160 (U160), and 240 (U240) kg N ha−1; 40% applied as a basal fertilizer and 60% top-dressed at jointing stage) and controlled-release urea (CRU) (at 60 (C60), 120 (C120), 180 (C180), and 240 (C240) kg N ha−1; all applied as a basal fertilizer) with no N application as a control (CK). The continuous release of N from CRU matched well with the N demands of crop throughout entire growing stages. Soil NO3−-N content varied less and peaked shallower in CRU than that in urea treatments. The differences, however, were smaller in winter wheat than that in summer maize seasons. The average yield of summer maize was the highest in C120 in CRU treatments and in U160 in urea treatments, and apparent N use efficiency (NUE) and N agronomic efficiency (NAE) were higher in C120 than in U160 by averages of 22.67 and 41.91%, respectively. The average yield of winter wheat was the highest in C180 in CRU treatments and in U240 in urea treatments with C180 increasing NUE and NAE by averages of 14.89 and 35.62% over U240, respectively. The annual yields under the two N fertilizers were the highest in C120 and U160. The results suggested that CRU as a basal fertilizer once could be a promising alternative of urea as split application in semiarid areas.

不同新型增效尿素对甜玉米产量及氮素利用率的影响

在粤北以甜玉米品种广甜2号为试验材料，研究不同新型增效尿素对甜玉米产量与氮素利用率的影响。结果表明：施用腐植酸尿素的甜玉米产量最高，显著高于普通尿素处理，提高了7.78% (p < 0.05)；控失尿素、聚能网尿素和腐植酸尿素的蛋白质和氨基酸含量均显著高于普通尿素处理；控释尿素、聚能网尿素、腐植酸尿素和含锌尿素处理的氮素累积量和氮素利用率均显著大于普通尿素处理，氮素利用率从17.19%提高到22.79%~24.56%；各处理中产值和净收益最高的是腐殖酸尿素处理，其次为聚能网尿素处理，其中腐殖酸尿素处理净收益比普通尿素处理提高14.5%。综合来看，施用腐植酸尿素和聚能网尿素有利于增加甜玉米产量和氮素积累，改善籽粒品质，提高氮素利用率和增加净收益。 A field experiment was conducted to determine the effects of different kinds of novel synergistic urea on yields and nitrogen use efficiency of sweet corn variety (Guangtian 2) in North Guangdong province of China. The results showed that corn yields in the treatment of humic acid urea were the highest, increased significantly (7.78%, p < 0.05) compared with that of common urea treatment. The protein and amino acid content of corn kernel under humic acid urea, Ju-Neng-Wang urea and controlled release urea treatments were significantly higher than that of common urea treatment. The humic acid urea, controlled release urea, Ju-Neng-Wang urea and zinc urea treatments could help the crop to increase nitrogen accumulation amount significantly compared with common urea treatment, and the N use efficiency was improved from 17.19% to 22.79%-24.56%. The humic acid urea treatment got the highest output and net income, followed by Ju-Neng-Wang urea, and the net income of humic acid urea treatment increased by 14.5% than common urea treatment. Taken together, application of humic acid urea and Ju-Neng-Wang urea could significantly enhance the yield and accumulation of N for sweet corn, improve the quality of sweet corn, and increase N use efficiency and net income.

Controlled Release Urea Improved Nitrogen Use Efficiency and Yield of Wheat and Corn

Nitrogen fertilizer is important for improving wheat (Triticum aestivum L.) and corn (Zea mays L.) yields, but inappropriate application methods and excessive amounts lead to low N use efficiency and high N losses through leaching. To investigate the effects of controlled‐release urea (CRU) on crop yield and soil fertility, a field experiment was conducted from 2012 to 2014 in China. The 100% (180 kg ha−1) and 70% (126 kg ha−1) of the local practice N rates with CRU and urea were used. The results revealed that the release curves of CRU in the natural field corresponded well to the N requirements of wheat and corn plants, and a positive linear correlation was observed between release rates and days after buried in soil. Consequently, the CRU treatments achieved significantly higher wheat and corn yield by 8 to 12% and 9 to 11%, respectively, compared with urea treatments at the same N rate. Reducing N rate of CRU by 30% produced the same yield as with the 100% N rate of urea. The agronomic nitrogen use efficiency (NUE) was significantly increased and the leaching of soil N was reduced by CRU. The acidification rates and leaching of exchangeable Ca2+, K+, Na+ contents were reduced, base saturation and available P improved by application of CRU compared with urea. Therefore, the results suggested that a 30% decrease of CRU in the recommended application rate of N, can be an effective measure to save consumption input of N fertilizer.Core Ideas Nitrogen release rates of controlled‐release urea in field condition corresponded well to the N uptake of crop plants. A 30% decrease in the application rate of N is possible with controlled‐release urea compared to urea. The application of controlled‐release urea increased crop yield, N use efficiency, net farm profit, and soil fertility.

Long‐Term Effects of Controlled‐Release Urea on Crop Yields and Soil Fertility under Wheat–Corn Double Cropping Systems

The long‐term effects of controlled‐release urea (CRU) on crop yields and soil properties were investigated in lysimeters under wheat and corn rotation system from 2009 to 2014 in northern China. The CRU included polymer‐coated urea (PCU), sulfur‐coated urea (SCU), and polymer coating of sulfur‐coated urea (PSCU) was applied at 147, 210 kg N ha−1 for wheat and 262.5, 375 kg N ha−1 for corn and the urea was applied at 210 kg N ha−1 for wheat and 375 kg N ha−1 for corn. Results showed that the N release characteristics of three kinds of CRU in field condition were all closely matched to the N requirement of crops. Consequently, the CRU treatments improved wheat and corn yields by 3.2 to 10.1% and 4.9 to 11.1%, increased apparent N use efficiency by 45.9 to 53.8% in wheat, and 36.2 to 45.4% in corn, respectively, compared with urea. Furthermore, the PSCU achieved the highest and the most stable crop yields among CRU. Even reducing CRU rate by 30% produced the same yields as with the 100% rate of urea. In addition, soil total N and organic matter contents in CRU were effectively increased in the topsoil of 0 to 20 cm after 5 yr. Therefore, long‐term application of CRU had great potential to increase wheat–corn yields, N use efficiency, reduce application frequency, improve soil fertility, decrease the leaching of soil NO3−–N and NH4+–N, and also relieve soil pH decreased.Core Ideas The long‐term effect of controlled‐release urea on crop yield and soil chemical properties was studied. The N release rates of controlled‐release urea were closely matched to the demand for N during the whole growth periods of crops. The wheat and corn yields were increased by 3.2 to 10.1% and 4.9 to 11.1% by controlled‐release urea fertilization, compared with urea treatment.

Suppression of Ammonia Volatilization from Rice–Wheat Rotation Fields Amended with Controlled‐Release Urea and Urea

The critical period of ammonia volatilization (AV) is an important indicator in the development of control measures of AV. A field trial was performed for 2‐yr with zero‐N fertilization control (CK), controlled‐release‐urea (CRU), and urea in rice (Oryza sativa L.)–wheat (Triticum aestivum L.) rotation system to investigate AV. The N application dosage was 255 and 225 kg N ha−1 in rice and wheat season, respectively. The CRU was applied once as basal fertilization in each growing seasons. Urea was applied twice in the rice season, while it was applied three times in the wheat season. The results revealed that AV applied with urea was 61.4 and 57.3% higher than that with CRU in 2010–2011 and 2011–2012, respectively. The AV applied with CRU and urea predominately occurred at the rice flooding period, which accounted for 83.2 to 86.6% and 95.5 to 96.9% of AV at the entire rice season and for 48.2 to 49.6% and 67.2 to 70.4% of AV in the rice–wheat rotation period, respectively. No obvious difference was observed between urea and CRU treatments concerning grain yield, N concentration, and removal N of aboveground biomass. An obvious influence of rainfall on AV was documented because rainfall significantly reduced AV during the rice growth, while the rainfall before N fertilization could significantly increase AV in the wheat season. Therefore, the rainfall should be considered when applying N fertilizer, CRU should be recommended to use during the rice flooding period to decrease the AV rate. Ammonia volatilization predominately occurs in the flooded period of rice season. Ammonia volatilization in the urea treatment is more than 50% higher than that in the controlled‐release urea treatment. Controlled‐release urea fertilization is an eco‐friendly, labor‐saving, and effective technique in minimizing ammonia volatilization. In order to decrease ammonia volatilization as much as possible, irrigation and rainfall should be considered when designing N fertilization programs.

Effects of slow/controlled release urea on annual CH4 and N2O emissions in paddy field.

Present study examined the influence of different types of slow/controlled release urea on rice yield and annual greenhouse gas emissions in a paddy field, and assessed the greenhouse gas intensity (GHGI, equivalent to global warming potential GWP/rice yield). The results indicated that the optimized fertilization (OPT) treatment recorded the similar yield with reduced nitrogen fertilizer (21.4%) supply compared with the farmers' fertilizer practice (FFP) treatment, and decreased the annual emissions of CH4 (12.6%) and N2O (12.5%) during the rice season, and N2O emission (33.3%) during the fallow period. Application of controlled release urea (CRU) reduced CH4 emission by 28.9% during the rice-growing season with respect to OPT treatment, and showed negligible CH4 emission during the fallow season. However, nitrification inhibitor (DMPP) treatment was found to reduce the CH4 emissions by 41.6% and 76.9%, and N2O emissions by 85.7% and 6.5%, during the rice growing season and fallow season, respectively, compared with OPT treatment. In the fallow season, the N2O emissions accounted for 76.8%-94.9% of annual N2O emissions, which was clearly a key point for evaluation of greenhouse gas emissions in paddy. The average values of GHGI in OPT, CRU and DMPP treatments were 0.50, 0.41 and 0.33 kg·kg-1, respectively. Considering the benefits of higher rice yield and lower annual greenhouse gas emissions, combined application of urea and nitrification inhibitor could be the best combination in paddy fields.

Application of Controlled-Release Urea in Rice: Reducing Environmental Risk While Increasing Grain Yield and Improving Nitrogen Use Efficiency

ABSTRACTThe low use efficiency of nitrogen (N) in rice production attributes to N losses and environmental pollution. One of the ways to improve N use efficiency is by using controlled-release urea (CRU). Field experiments in consecutive three years were conducted to compare the effects of six different types of CRU fertilizers on yield and N accumulation in straw and grain of rice. The special purpose was to provide information for application of CRU in rice. For three seasons, CRU-treated plants had significantly greater grain yields than conventional urea-treated (total N as basal fertilizers, Nt) plants. The greatest grain yields were obtained from CRU-3, CRU-4, and CRU-3 treatment in 2012, 2013, and 2014, respectively. The N accumulation in rice straws and rice grains of the CRU-treated plots was significantly greater than that of the Nt treatment. Compared with that of the Nt treatment, CRU treatments increased the N use efficiency significantly, although there were differences among the six types of CRU fertilizers. It can be inferred that CRU performed significantly better than conventional urea. Generally, CRU-3 and CRU-6 were the best CRU fertilizers used in rice production in Jianghan Plain, China.

Coupling effects of plastic film mulching and urea types on water use efficiency and grain yield of maize in the Loess Plateau, China

Increasing water and nitrogen use efficiency is important for sustainable agricultural development, especially in arid and semi-arid areas. A two-year field experiment was conducted to investigate the effects of field management practices on soil water, maize development, and yield on the Loess Plateau, China. The experiment adopted a split-plot design, with three mulchings as the main-plot treatments and two urea types (225Nha−1) as the sub-plot treatments. Treatments were established as: (1) no plastic film mulching with urea (NU), (2) no plastic film mulching with controlled release fertilizer (NC), (3) white plastic film mulching with urea (WU), (4) white plastic film mulching with controlled release fertilizer (WC), (5) black plastic film mulching with urea (BU), and (6) black plastic film mulching with controlled release fertilizer (BC). The soil water storage was higher under black plastic film mulching than that under other treatments for most sampling dates within the two experimental years, especially in the second maize growing season. Higher soil water stimulated maize growth, as indicated by a higher plant height, leaf area index, and greater biomass accumulation; thus, the highest grain yield (16.64tha−1) and water use efficiency (28.3kgha−1mm−1) in 2014 was recorded in BC plots, which were higher by 34.5% and 34.8%, respectively, compared with those in NU. White plastic film mulching also increased the soil water content and promoted maize development, grain yield, and water use efficiency; thus, higher grain yield (16.02tha−1) and water use efficiency (26.5kgha−1mm−1) were recorded in WC plots in 2014. In the two experimental years, controlled release urea treatments always produced significantly higher maize yields than conventional urea treatments, except the NC plots in 2013. However, significant soil water depletion in the deeper (>120cm) soil layers was detected at harvest time in 2014 under BC treatment, indicating that higher yields might not be sustained in long time periods. In conclusion, plastic film mulching, particularly black plastic film mulching combined with controlled released fertilizer, could improve the water use efficiency and suitably meet the nitrogen requirements of maize, thereby increasing the grain yield in the Loess Plateau, China.

Long-term effects of controlled release urea application on crop yields and soil fertility under rice-oilseed rape rotation system

Nitrogen (N) fertilizer has played an important role in increasing rice and oilseed rape yields, but more than half of the N fertilizer applied into the field has been lost and results in not only an environmental hazard but also a substantial economic loss. Thus, the controlled release N fertilizer was expected to reduce the labor cost from fertilizer dressing, to the convenience of fertilizers application and to increase N use efficiency. A 7-year field fertilization experiment applied controlled-release urea (CRU) 100% (180kgha−1), 70% (126kgha−1) and 50% (90kgha−1) of the recommended N fertilizer to explore its effects on crops yield and soil fertility under the rice (Oryza sativa L.)-oilseed rape (Brassica napus L.) rotation system in Hubei province of China. Meanwhile the equivalent rates of N as common urea were supplied as split applications in different growth stages as the control. The N release characteristic of CRU in field condition was closely matched to the demand for N during the whole growth periods of crops. Consequently, the CRU treatments achieved significantly higher rice and oilseed rape yield by 6.1–8.2% and 6.3–15.5%, the mean nitrogen use efficiency (NUE) of CRU treatments was increased by 15.4–38.4%, and the average annual net profit was also increased by 16.0–20.8%, compared with urea treatment at the same N rate. For each type of N fertilizer, the yield increased as the input N rate increased. However, reducing CRU rate by 30% produced the same yield of rice and oilseed rape as with the 100% rate of urea. And, the rice yield of CRU50% treatment was even showed no significant with Urea100% treatment. The contents of nitrate N (NO3−-N) and ammonium N (NH4+-N) were higher in 0–40cm soil of CRU treatments than urea treatments over 7-year fertilization in 2013, but the opposite trend was found in 60–100cm soil, which indicating that CRU decreased the NO3−-N and NH4+-N leaching to deep in the soil. The contents of total N and organic matter were increased by applying CRU for 7 years compared with urea fertilizer. Although the contents of available P and K were increased over the 7 years of fertilization and cultivation, no prominent difference was observed between CRU70% and Urea100%. The results suggest that a 30% decrease in the recommended application rate of N is possible with CRU while maintaining the same yield, preserving the soil fertility and also labor/time-saving.

Controlled release urea improved the nitrogen use efficiency, yield and quality of potato (Solanum tuberosum L.) on silt loamy soil

Numerous studies on the traits of controlled release urea in agronomic production and the environmental protection were conducted in various crops system. However, understanding the effect of controlled release urea on potato production and nitrogen use efficiency was currently limited. In the present study, the effect of newly developed controlled release urea (CRU) including polymer coated urea (PCU) and polymer coating of sulfur-coated urea (PSCU) on the N use efficiency, tuber yield and quality of potato (Solanum tuberosum L.) that was grown on silt loamy soil were investigated in a field experiment over 2 yr at different sites. The application rate of polymer-coated urea (PCU) and urea was 150kgNha−1, and polymer sulfur-coated urea (PSCU) was applied at 150kgNha−1 and 225kgNha−1. The N release rates from CRU synchronized the N requirement of potatoes at different stages. The CRU treatments significantly increased total tuber yields by 8.77–19.88% in 2012 and 14.36–26.46% in 2013 in comparison with the urea treatment during the same year. The marketable tuber yield percentage was pronouncedly promoted by the application of PCU and PSCU in both years. N fertilization significantly enhanced the vitamin C, soluble protein and starch content. The significant difference of vitamin C concentration in tuber was only observed in 2013 between PCU and PSCU treatments. The application of PCU and PSCU markedly improved the N agronomic efficiency and apparent N use efficiency, but obviously decreased the N physiological efficiency relative to urea treatment in 2012 and 2013. Furthermore, enhancing dose of PSCU did augment total tuber yield and did not increase the marketable yield percentage, but decreased the apparent N use efficiency compared with PSCU treatment. Consequently, moderate amounts (150kgNha−1) of PSCU and PCU are recommended to replace urea for gaining greater yields of potato and nutrient use efficiency.

Nitrous Oxide and Methane Fluxes During the Maize Season Under Optimized Management in Intensive Farming Systems of the North China Plain

Addressing concerns about mitigating greenhouse gas (GHG) emissions while maintaining high grain yield requires improved management practices that achieve sustainable intensification of cereal production systems. In the North China Plain, a field experiment was conducted to measure nitrous oxide (N2O) and methane (CH4) fluxes during the maize (Zea mays L.) season under various agricultural management regimes including conventional treatment (CONT) with high N fertilizer application at a rate of 300 kg N ha−1 and overuse of groundwater by flood irrigation, optimal fertilization 1 treatment (OPT1T), optimal fertilization 2 treatment (OPT2T), and controlled-release urea treatment (CRUT) with reduced N fertilizer application and irrigation, and a control (CK) with no N fertilizer. In contrast to CONT, balanced N fertilization treatments (OPT1T, OPT2T, and CRUT) and CK demonstrated a significant drop in cumulative N2O emission (1.70 v.s. 0.43–1.07 kg N ha−1), indicating that balanced N fertilization substantially reduced N2O emission. The values of the N2O emission factor were 0.42%, 0.29%, 0.32%, and 0.27% for CONT, OPT1T, OPT2T, and CRUT, respectively. Global warming potentials, which were predominantly determined by N2O emission, were estimated to be 188 kg CO2-eq ha−1 for CK and 419–765 kg CO2-eq ha−1 for the N fertilization treatments. Global warming potential intensity calculated by considering maize yield was significantly lower for OPT1T, OPT2T, CRUT, and CK than for CONT. Therefore, OPT1T, OPT2T, and CRUT were recommended as promising management practices for sustaining maize yield and reducing GHG emissions in the North China Plain.

Effects of Different Mixing Rates of Controlled-Release Urea and Common Urea on Grain Yield and Nitrogen Use Efficiency of Summer Maize

Using controlled-release urea (CRU) with releasing period of 60 d and conventional urea (U) as experimental materials, the effects of different mixing rates of CRU (0, 10%, 30%, 50%, 100%) and U with the equality of nitrogen fertilization every treatment on photosynthetic efficiency, grain filling rate, grain yield, economic profits and nitrogen use efficiency of summer maize were studied. Results were as follows: (1) Net photosynthetic rates, chlorophyll contents and nitrate reductase activity in ear leaves of treatments with different ratio of CRU were always higher , the grain filling was started-up faster and grain active filling duration was longer than those of U treatment. (2) With the increase of proportion of CRU, the grain yield was increased firstly and then gradually decreased. Compared with U treatment, the increase of grain yield in CRU+U treatments was 2.90%, 7.91%, 9.48%, and 5.68% in turn and the increase of economic profits was 397.34, 1 077.65, 1 263.94, and 611.3 yuan ha?1 in turn. (3) In all treatments, nitrogen agronomy efficiency was 8.31, 10.55, 11.81, 12.5, and 9.46 kg kg?1 in turn, among them, CRU treatments showed 1.15–4.19% more than U treatment; nitrogen use efficiency was 29.71%, 31.83%, 38.49%, 40.72%, and 44.63% in turn, among them CRU treatments showed 2.12–14.92% more than U treatment. (4) Applying CRU with a mixing ratio of 50% was most beneficial to increase the yield of summer maize.

Responses of photosynthesis, chlorophyll fluorescence, and grain yield of maize to controlled‐release urea and irrigation after anthesis

AbstractControlled‐release urea (CRU) is a new type of urea, which may increase crop nitrogen (N)‐use efficiency compared with conventional urea (CU), but the conditions where it outperforms urea are not well defined. A field experiment assessing responses of plant growth and grain yield of maize to CRU and irrigation was conducted on a typical agricultural farm in Shandong, China. Five treatments of the two types of urea (75, 150 kg N ha–1, 0 kg N ha–1) were applied as basal fertilizer when sowing maize, and two water treatments (W0 and W1) were used 23 d after anthesis. Net photosynthetic rate (PN) and chlorophyll concentration as well as leaf‐area index (LAI) increased significantly by both CRU and CU application, with the increases being larger in CRU‐treated plants than in CU‐treated plants at grain filling and maturing stages. CRU significantly enhanced the maximum photochemical efficiency (Fv / Fm), PSII coefficient of photochemical fluorescence quenching (qP), and actual quantum yield of PSII electron transformation (ΦPSII) but decreased the nonphotochemical quenching (NPQ). Cob‐leaf N concentration of CRU‐treated plants was significantly higher than that of CU‐treated plants under no irrigation, but not in the irrigation treatment 30 d after anthesis. Significant positive correlations were found between cob‐leaf N concentration and PN both with and without irrigation. Grain yield of maize was significantly higher in the CRU treatment than in the CU treatment under both irrigation conditions. In conclusion, CRU as a basal application appeared to increase the N‐use efficiency for maize relative to CU especially by maintaining N supply after anthesis.

Abscisic acid and aldehyde oxidase activity in maize ear leaf and grain relative to post-flowering photosynthetic capacity and grain-filling rate under different water/nitrogen treatments

This study investigated changes in leaf abscisic acid (ABA) concentrations and grain ABA concentrations in two maize cultivars and analyzed the following relationships under different water/nitrogen treatments: leaf ABA concentrations and photosynthetic parameters; leaf ABA concentrations and grain ABA concentrations; leaf/grain ABA concentrations and grain-filling parameters; and aldehyde oxidase (AO,EC 1.2.3.1) activities and ABA concentrations. The ear leaf average AO activities and ABA concentrations were lower in the controlled release urea treatments compared with the conventional urea treatments. The average AO activities in the grains were higher in the controlled release urea treatments, and the ABA concentrations were significantly increased at 11-30 DAF. The Pn and ABA concentrations in ear leaves were negatively correlated. And the Gmean were positively correlated with the grain ABA concentrations at 11-30 DAF and negatively correlated with the leaf ABA concentrations at 20 and 40-50 DAF. The grain ABA concentrations and leaf ABA concentrations were positively correlated. Thus, the Gmean were closely related to the AO activities and to the ear leaf and grain ABA concentrations. As compared to other treatments, the subsoiling and controlled release urea treatment promoted the uptake of water and nitrogen by maize, increased the photosynthetic capacity of the ear leaves, increased the grain-filling rate, and improved the movement of photosynthetic assimilates toward the developing grains. In the cultivar Z958, higher ABA concentrations in grains at 11-30 DAF and lower ABA concentrations in ear leaves during the late grain-filling stage, resulted in higher grain-filling rate and increased accumulation of photosynthetic products (relative to the cultivar D3).

CONTROLLED-RELEASE UREA FOR RICE PRODUCTION AND ITS ENVIRONMENTAL IMPLICATIONS

Controlled-release urea (CRU) and its placement method in rice production were investigated during 2007 and 2008 seasons. Controlled-release urea was applied at 62.5, 125, and 187.5 kg nitrogen (N) ha−1, and the urea was 187.5 kg N ha−1. All the CRU treatments were applied to the nursery beds once, and they were brought into the paddy field during transplanting, while the urea treatment was split into three applications from the plowing to the harvest. The results showed that rice seedlings with CRUs germinated and grow well and there was no salt damage at the nursery stage. The CRU treatment with 125 kg N ha−1 had 33% less N than urea treatment (187.50 kg N ha−1), but it produced significantly higher grain and straw yields, higher total N uptake and total apparent N uptake efficiency. In addition, all the CRU treatments effectively decreased floodwater ammonium (NH4 +)-N and nitrate (NO3 −)-N concentrations, pH, and N runoff.

Effects of controlled-release urea application on the growth, yield and nitrogen recovery efficiency of cotton

Field experiments were conducted to study the effects of the controlled release urea (CRU) application on growth yield and nitrogen recovery efficiency of cotton in the main cotton zone of the Yangtze River basin in 2010. Different nitrogen levels were set in order to determine the suitable dosage of CRU on cotton. The special purpose was to provide evidence for the CRU application in cotton fields. The results show that the application of CRU promotes the growth of cotton significantly and enhances the nitrogen supply in the whole period. Compared to the treatment with total N as base fertilizer (UB), the bod, flower, little bolls and total bolls are increased significantly. There are no significant differences in the yield between the CRU treatment and the treatment of controlled release urea and urea combined application (60%CRU + 40%U), but an increase by 12.38%-22.67% compared to the UB treatment, and an increase by 4.49%-7.23% compared to the treatments of total N split application (UD). The nitrogen uptake of CRU treatment was significantly increased by 13.01%-48.32% and 30.27%-13.01% than UB treatment and UD treatment, respectively. The nutrient recovery efficiency of CRU treatment is increased by 16.42-20.59, 5.92-11.29 and 4.22-12.59 percentage points compared to the UB treatment, UD treatment and 60%CRU + 40%U treatment, respectively. In this study, there was a good linearity relationship between the cotton yield and amount of CRU in Wuxue site. The yield of cotton response to amount of CRU could be described by the model of linear plus plateau in Jingzhou site.

Copper-based foliar fertilizer and controlled release urea improved soil chemical properties, plant growth and yield of tomato

This experiment was carried out to determine the influence of copper-based foliar fertilizer and controlled release urea on soil chemical properties, plant growth and yield of tomato. Tomato plants were grown in pots under field condition. Controlled release urea (CRU), comparing with common urea, was placed into soil before transplanting seedlings. Plants were sprayed with copper-based foliar fertilizer with added zinc (CFF+Zn), a novel foliar formulation based on traditional Bordeaux mixture, at 43, 50, 70 and 97 days after transplanting (DAT) compared with plants sprayed with CFF and Kocide 2000 (KCD). Water-sprayed plants and no fertilized soil served as the controls. CRU provided the significantly higher NO3-N concentration in soil than common urea at the end of the experiment. Under the same placement of CRU, the application of CFF+Zn increased the available fraction of Cu in soil and thus made influence on soil pH and EC. At 89 DAT, plant height and leaf chlorophyll content were higher in plants sprayed with CFF+Zn compared with water-sprayed plants. Leaves from CFF, CFF+Zn and KCD treatments showed significantly higher total Cu concentration than control at 65 and 89 DAT. Without the placement of soil fertilizer, CFF treated plant increased the yield by 20.75% compared with water-sprayed plant. CRU treatment accompanied with water application significantly increased total yield by 28.58% compared with the Urea treatment. Accompanied with the same placement of CRU, yields of the plants sprayed with CFF+Zn were 27.07%, 20.73% and 20.46% more than the yields of water, CFF and KCD-sprayed plants, respectively. These results clearly indicate that the application of copper-based foliar fertilizer with added zinc and controlled release urea is favorable for tomato.

Controlled Release Urea Improved Nitrogen Use Efficiency, Yield, and Quality of Wheat

The effects of newly developed controlled release urea (CRU) and its placement method on the N use efficiency and nutritional quality of winter wheat (Triticum aestivum L.) grown on a loam soil were investigated during 2 yr. The winter wheat was grown on a loam soil. The CRU was applied at 0, 75, 150, and 225 kg N ha−1 and the urea was applied at 225 kg N ha−1 The CRU was applied with wheat seeds during sowing while the urea treatment was split into two applications: two‐thirds applied during sowing and one‐third at the 5‐tiller stage (Z25). Results showed that N release rates of CRU fit N requirements of wheat and the placement of wheat seeds with CRU improved wheat's apparent N uptake efficiency by 28.5% compared to urea treatment. Although the CRU treatment at 150 kg N ha−1 had one‐third less supplied N than that of conventional urea treatment (225 kg N ha−1), the wheat with CRU at 150 kg N ha−1 produced 6.5% more grain. In addition, at the same or one‐third reduced amount of N compared with the conventional urea treatment, CRU significantly increased the contents of Fe and Mn, providing additional nutrition and quality to the wheat grain.