Split Application Of Urea Research Articles

Influences of Chemical Fertilizers and a Nitrification Inhibitor on Greenhouse Gas Fluxes in a Corn (Zea mays L.) Field in Indonesia

The influences of chemical fertilizers and a nitrification inhibitor on greenhouse gas fluxes (N(2)O and CH(4)) in a corn field in Indonesia were investigated using a closed chamber. Plots received 45+45 kg-N ha(-1) of nitrogen fertilizer by split applications of urea, a single application of controlled-release fertilizer (CRF-LP30) or urea+dicyandiamide (DCD; a nitrification inhibitor), and no nitrogen application (control). Cumulative amounts of N(2)O emitted from the field were 1.87, 1.70, 1.06, and 0.42 kg N(2)O-N ha(-1) season(-1) for the urea, CRF-LP30, urea+DCD, and control plots, respectively. The application of urea+DCD reduced the emission of N(2)O by 55.8% compared with urea. On the other hand, the soil acted as a sink for CH(4) in the CRL-LP30, control, and urea+DCD plots with value of -0.09, -0.06 and -0.06 kg CH(4)-C ha(-1) season(-1), respectively. When the viability of AOB (ammonia-oxidizing bacteria) and NOB (nitrite-oxidizing bacteria) were monitored, AOB numbers were correlated with the N(2)O emission. These results suggest that 1) there is a potential for reducing emissions of N(2)O by applying DCD, and 2) corn fields treated with CRF or urea+DCD can act as a sink for CH(4) in a tropical humid climate.

Nitrate leaching and nitrogen recovery following application of polyolefin-coated urea to potato.

High N fertilizer and irrigation amounts applied to potato (Solanum tuberosum L.) on coarse-textured soils often result in nitrate (NO3) leaching and low recovery of applied fertilizer N. This 3-yr study compared the effects of two rates (140 and 280 kg N ha(-1)) of a single polyolefin-coated urea (PCU) application versus split applications of urea on 'Russet Burbank' potato yield and on NO3 leaching and N recovery efficiency (RE) on a loamy sand. Standard irrigation was applied in all years and excessive irrigation was used in another experiment in the third year. At the recommended rate of 280 kg N ha(-1), NO3 leaching during the growing season was 34 to 49% lower with PCU than three applications of urea. Under standard irrigation in the third year, leaching from five applications of urea (280 kg N ha(-1)) was 38% higher than PCU. Under leaching conditions in the first year (> or = 25 mm drainage water in at least one 24-h period) and excessive irrigation in the third year, PCU at 280 kg N ha(-1) improved total and marketable tuber yields by 12 to 19% compared with three applications of urea. Fertilizer N RE estimated by the difference and 15N isotope methods at the 280 kg N ha(-1) rate was, on average, higher with PCU (mean 50%) than urea (mean 43%). Fertilizer N RE values estimated by the isotope method (mean 51%) were greater than those estimated by the difference method (mean 47%). Results from this study indicate that PCU can reduce leaching and improve N recovery and tuber yield during seasons with high leaching.

Evaluation of Polyolefin-coated Urea for Potato Production on a Sandy Soil

Field studies were conducted on a Hubbard loamy sand (sandy, mixed, frigid Entic Hapludoll) during 1996 and 1997 at Becker, Minn., to evaluate the effect of a polyolefin-coated urea (POCU) fertilizer (Meister, Chisso Co., Japan) on yield and quality of irrigated `Russet Burbank' potatoes (Solanum tuberosum L.). The POCU was a 3:1 mixture of 70-day and 50-day release formulations, respectively, based on historical soil temperatures at the site. The study compared five banded nitrogen (N) rates (110, 155, 200, 245, and 290 kg·ha-1 N) as a split application of urea applied at emergence and hilling, vs. POCU applied at planting. All plants received an additional 30 kg·ha-1 N as monoammonium phosphate band-applied at planting. Yields were higher in 1996 because of cooler temperatures and poor tuber set in 1997. Total and marketable yields averaged, respectively, 3.9 and 3.3 Mg·ha-1 higher with POCU than with urea. Total yield was not affected by rate of N application regardless of source, but marketable yield increased linearly with N rate. The yield of marketable tubers larger than 170 g increased linearly with N rate in both years. Gross return was 10% higher with POCU than with urea, but estimated net return showed a significant sourc × N rate interaction. The net return increased by $3.13 per kg of urea-N applied, but there was no significant change across POCU application rates.

Nitrogen management and cultivar effects on rice yield and nitrogen use efficiency in Northeast Thailand

For improving nitrogen (N) use efficiency and yield of rainfed lowland rice, N management and cultivar experiments were conducted at Ubon Ratchathani, Northeast Thailand. In the N experiment, Khao Dawk Mali 105 (KDML105), one of the leading cultivars in Northeast Thailand, was grown under different N management methods including different N rates in frequent split urea application and the use of organic matter and slow release fertiliser (SRF). In the cultivar experiment, 18 cultivars of different origins were compared for growth, yield and N uptake under irrigated and well-fertilised conditions. No water stress developed in any experiment. The leaf area index and dry weight increased and the harvest index decreased linearly with plant N uptake, irrespective of N management methods. Grain yield of KDML105 attained the maximum of 4 t ha −1 at the N uptake of about 40, 80 and 90 kg ha −1 at panicle initiation, heading and maturity, respectively. The frequent split N application and use of SRF improved the fertiliser N recovery efficiency (apparent fertiliser N uptake per unit applied N), although they did not substantially increase agronomic efficiency (increment of yield per unit applied N) compared with the results of previous workers. These results suggest that yield of KDML105 can be improved by optimising the plant N uptake through increased fertiliser N recovery efficiency. Among 18 cultivars tested, Urumamochi, Taichung65, Takanari, IR72 and Taino70 had higher yields despite their shorter growth durations compared with KDML105. Although the physiological efficiencies of N use in terms of plant dry matter production (dry matter produced per unit N uptake) were similar among all cultivars, those in terms of yield were higher in Taichung65, Takanari, IR72 and Taino70 than in KDML105 because of their higher harvest indices. Thus, these four cultivars are suggested to have two important characteristics required for cultivars adapted to rainfed lowland conditions in Northeast Thailand: the shorter growth duration to avoid late season drought and the higher physiological efficiency of N use for yield production.

N 2O and CH 4 emission and CH 4 consumption in a sugarcane soil after variation in nitrogen and water application

Nitrous oxide (N 2O) and methane (CH 4) exchanges between the soil and the atmosphere are influenced by management practices currently used in agriculture. This study was conducted to determine whether N 2O and CH 4 emission and CH 4 consumption in a trash blanketed sugarcane soil could be influenced by changed N fertiliser practice and variation in soil water content. Microplots were placed in rows of sugarcane and urea and ammonium sulphate (both 99 atom % 15N excess) applied to the soil surface, urea as both a split application of 80 kg N ha −1 and a full rate of 160 kg N ha −1 and ammonium sulphate at 160 kg N ha −1. Sugarcane trash (15 t ha −1) was applied to the surface of all microplots. Water was then added to all microplots to achieve water contents of 80% water-filled pore space (WFPS) in half the plots and saturation in the other half. Initially, the application of urea at 160 kg N ha −1 to microplots at 80% WFPS resulted in greater emission of ( 14N+ 15N)–N 2O than was recorded from the split urea and the ammonium sulphate treatments at both moisture regimes. A mean value of 47 g N 2O–N ha −1 d −1 was measured for this treatment compared with 18.5 and 15.2 g and 4.9 and 7.7 g N 2O–N ha −1 d −1 for the split urea and ammonium sulphate waterlogged and 80% WFPS treatments respectively. Greater emissions of ( 14N+ 15N)–N 2O were measured following 132 mm rainfall in February, with mean values of 214 and 143 g N 2O–N ha −1 d −1 being recorded for the waterlogged treatments of the split urea and ammonium sulphate treatments respectively. A decrease in the 15N–N 2O emission from the split urea treatment was the only difference recorded when comparing the initial ( 14N+ 15N)–N 2O and 15N–N 2O emissions from all treatments. 14N–N 2O appeared to be the major gaseous N product from this treatment initially. Total emission of 15N–N 2O ranged from 105 to 453 g N 2O–N ha −1, which represented between 25.3 and 23.4% of the total amount of N 2O evolved. CH 4 emission occurred from all microplots fertilised with urea whereas CH 4 consumption was measured in plots fertilised with ammonium sulphate only. CH 4 emission ranged from 297 to 1005 g CH 4–C ha −1 while CH 4 consumption ranged from 442 to 467 g CH 4–C ha −1. The application of ammonium sulphate and using a split application of urea initially decreased N 2O emissions but the delay in nitrification obtained from changing the type and rate of application of these fertilisers resulted in greater N 2O emissions later in the season when the soil moisture regime had changed. CH 4 emission and consumption were not affected by these management changes.

SOURCES OF BASAL N AND TIMES OF UREA -N SPLITS ON YIELD ATTRIBUTES AND YIELD OF IRRIGATED LOWLAND RICE

Field experiments were conducted at TNAU, Coimbatore during Nov. '95 to Sept. '96 to study the effect of two sources (green manure and urea) as basal N in combination with different times of urea splits on yield attributes of rice. The conjunctive use of green manure, on equal N basis as basal, was equally effective but did not have any yield advantage over the urea N. Split application of urea at active tillering was vital, when the basal N was applied as GLM. but not for urea N basal. Nitrogen to a medium duration rice variety may be applied in five splits. First top dressing after the basal (AT stage) is vary if basal N is given through green manure without starter N. But, when fertiliser N is applied as basal, an optimum dose of 20 kg N at active tillering is sufficient to maintain the tiller production. Higher N (40 kg) at AT stage increases the biomass production through unproductive tillers and that ultimately leads to poor HI. On the other hand, low N status critically reduces the tillering too. An additional dose of 20 kg a week after AT was found to be beneficial to improve the panicle efficiency and ultimately the grain yield. irrespective of basal N sources. Split application of N at heading stage seems so delicate. Increasing the rate of N more than 20 kg i.e., 30 or 40 kg N/ha resulted in poor grain yield by increased sterility.

Fertilizer 15Nitrogen Recovery by Corn, Wheat, and Cotton Grown with and without Pre‐Plant Tillage on Norfolk Loamy Sand

Cropping systems must efficiently use N inputs to be sustainable environmentally and economically. This research was conducted to determine the fate of 15N fertilizer that was applied to corn (Zea mays L.), wheat (Triticum aestivum L.), or cotton (Gossypium hirsutum L.) grown in a 2‐yr, three‐crop rotation on Norfolk (Typic Kandiudult) loamy sand. A total of 48, 2.3‐ by 2.3‐m microplots were established, half into plots that received surface tillage (disked) and half into non‐disked plots. Corn and wheat received a split application of urea [CO(NH2)2] plus ammonium nitrate (NH4NO3) solution (UAN) had a 5 atom percent (ATM%) 15N isotopic label. Cotton was fertilized with NH4NO3 containing a 5 ATM% label. The amounts of 15N removed in the harvested portion of treated and subsequent crops, recycled in crop residues, or remaining in the upper 90 cm of the soil profile were determined. Corn, wheat, and seed cotton yields ranged from 1485 to 7410, 1850 to 2270, and 120 to 2510 kg ha−1, respectively, with significant differences caused primarily by seasonal rainfall or temperature extremes. No‐till significantly increased cotton yield, presumably because of water conservation. Crop removal accounted for 20 to 34% of the fertilizer 15N, while another 20% was accounted for by soil profile analysis to a depth of 90 cm. Approximately 50% of the 15N was apparently lost through denitrification, volatilization, or leaching below the root zone. Most of this loss appeared to occur during the cropping season in which the 15N was applied. This suggests that for optimum fertilizer efficiency and environmental sustainability, crop production practices on Coastal Plain soils must account for all N sources that plants can draw upon, and should accommodate several fertilizer N management options including split applications, injection beneath the soil surface, and/or using less mobile forms.

Long-term measurement of denitrification in three contrasting pastures grazed by sheep

Three pastures—white clover and perennial ryegrass, a herbal ley comprising grasses and broadleaf species including legumes, and a perennial ryegrass sward fertilised with split applications of urea supplying 400 kg N ha −1 yr −1-were established in a randomised block experiment on a freely drained fine sandy loam (mixed mesic Dystric Eutrochrept) at Palmerston North, New Zealand ( ca latitude 40°S). Soil denitrification rates were measured periodically during 21 months when the pastures were rotationally grazed by sheep. N 2O production was measured using the acetylene-block technique adapted to soil cores incubated for 24 h in gas-tight chambers in the field. The influence of soil moisture, temperature, the availability of soil nitrate and the frequency of grazing on the denitrification rate was assessed. Soil temperatures (at 10cm depth) remained above 4–6°C, the lower limit for denitrification. The highest losses by denitrification occurred in winter when soil moisture was at or above field capacity for extended periods. The critical air-filled porosity below which denitrification was accelerated was found to be 17% v/v. When conditions were suitable, the rate of denitrification was controlled by the availability of NO 3 − and NO 2 −. In the Grass + N400 system, these were supplied principally by the hydrolysis and nitrification of urea fertiliser, but in the legume-based pastures the input of readily decomposable excretal N from the grazing animals had a marked effect on the supply of these substrates. Total denitrification loss was 3.4, 4.4 and 19.3 kg N ha −1 yr −1 for Grass-clover, Herbal ley and Grass + N400, respectively. The ratio of N −O: N 2lost from these pastures averaged 0.38,0.30 and 0.27, respectively. Irrespective of whether N was supplied to the pastures by symbiotic fixation or in fertiliser, N 2O emissions were 1–1.3% of the annual N input.

Effect of Nitrogen Source and Timing on Highbush Blueberry Performance

`Bluecrop' highbush blueberries (Vaccinium corymbosum L.) received various N fertilizer treatments for 5 years. Treatments were evaluated by measuring berry yields and leaf N levels annually and bush size after 5 years. Nitrogen fertilizers increased yields and leaf N levels compared with nonfertilized controls. Split applications of urea (half applied at budbreak, half at petal fall) resulted in 10% higher yields than the same amount in a single application at budbreak. Urea and two controlled-release fertilizers (CRF) with different dissolution rates (3 to 4 months, 8 to 9 months) resulted in similar yields and leaf N levels when compared at the same rate of N. The dissolution rate of the CRF materials did not affect yields or leaf N levels.

Uptake of nitrogen by Pinus radiata and retention within the soil after applying 15N-labelled urea at different frequencies. 1. Growth response and nitrogen budgets

The uptake of fertiliser-nitrogen and retention within the soil was determined after one growing season in a 2-year-old Pinus radiata plantation on coastal sand dunes at Christchurch, New Zealand. Applications of 15N-labelled urea enriched at 2.33 atom % excess were applied at different frequencies and in different seasons to single-tree root-isolated plots (area, 7 m 2). A single application of 90 g N per tree in spring was compared with either three by 30 or nine by 10 split applications. Applications of 30 g N per tree in either autumn, spring or summer were also compared. The uptake of fertiliser-nitrogen was about 20% of that applied for all treatments irrespective of frequency, rate or season of application. Uptake was positively correlated with the size of the tree at the time of application. Seventy-two percent of fertiliser-nitrogen was retained within the soil following the application of 30 g N in spring but only 39% for the single application of 90 g N per tree. Splitting the application increased the retention of fertiliser-nitrogen to 54% and 67% for the three-split and nine-split applications, respectively. Those trees receiving 90 g N showed a diameter response of 9% compared to controls. Height growth was not affected by fertiliser. Above-ground biomass was 19% higher than controls with the main increase being in foliage formed during the experiment (+26%). The largest growth responses were below ground with overall root biomass 55% higher than controls with fine roots (less than 2 mm) 80% higher. The only response to 30 g N per tree was below ground with fine-root biomass being 27% higher. Split applications of urea reduced losses of fertiliser, probably as leaching, but the increased nitrogen within the soil has not benefitted the trees in the first year. The relatively low losses from applying 30 g N per tree and the increase in fine-root biomass suggest that an optimal fertiliser strategy in young pines would be to apply a single small dressing followed by a heavier application a year later when root density and sink size have increased. There is no evidence for the superiority of applying nitrogen in any particular season.

Nitrogen‐15 Recovery in Winter Wheat as Affected by Application Timing and Dicyandiamide

AbstractNitrification inhibitor amendment to fall‐applied N for winter wheat may reduce denitrification and leaching losses of N by maintaining N in ammoniacal form. A field study on a Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Paleudult) compared fall application of 15N‐labeled urea with and without dicyandiamide (DCD) and split urea application in fall and spring. Grain yield (mean 4.26 Mg ha−1) increased with N rate (67, 101, and 134 kg N ha−1), but was not affected by DCD or time of N application. Recovery of 15N in wheat the first year (mean 53%) was not affected by DCD or time of N application. Immobilization of 15N was 21, 20, and 15% with the fall N plus DCD, split‐applied N, and fall N treatments, respectively. Nitrogen‐15 leached at harvest was less with fall N plus DCD or split‐applied N than with fall N only. Denitrification estimates, calculated as 15N not accounted for, were not affected by DCD or timing of N. In the second year, 101 kg N ha−1 of unlabeled urea was split applied across the entire experiment. Grain yields averaged 2.07 Mg ha−1 and were not affected by N rate, DCD, or timing of N application from the previous year. Percent recovery of 15N averaged 1.0 and 0.9% in the grain and straw, respectively, or about 10% of the 15N immobilized the year before. Recovery of 15N in the second year was significantly higher in the straw and roots following split‐applied N or fall N plus DCD, compared with following fall N alone. This suggests that nitrification inhibitors can affect N uptake of a second‐year crop by enhancing biological immobilization of fertilizer N.

Sulfur-coated Urea as a Slow-release Nitrogen Source for Onions

Abstract Field studies with onions (Allium cepa L. cv Monarch) were conducted in 1980 and 1981 to compare preplant-banded sulfur-coated urea (SCU) with preplant-banded and split applications of urea. Treatments were evaluated at two N rates, 56 and 224 kg·ha−1. Root NO3-N and soil NO3-N concentrations in bed centers indicated slower release of N from SCU than from urea. Nevertheless, total and large bulb (> 76 mm in diameter) yields and N uptake in onion bulbs and leaves from SCU were significantly higher under low-N conditions than with preplant urea, but did not differ significantly from split urea treatments.

The effect of water and nitrogen on wheat yield on a Zambian soil I. Influence of irrigation schedules and nitrogen piacement

Abstract Zambia possesses tremendous potential in implementing multiple cropping systems. To utilize this potential, an expansion of irrigated crops grown during the dry season (May to October) must be achieved. However, this implies the need for a more rational and efficient use of water and fertilizer. A two‐year study was, therefore, conducted to find out the response of wheat (Triticum aestivum L.) to different irrigation regimes, different rates and methods of placement of urea N. Differential irrigation commenced after tillering either on a weekly, every two week, or every three week basis with irrigation water applied at 70, 60, and 50 percent of the total pan evaporation during the whole irrigation interval, respectively. Maximum yields were obtained with weekly irrigation and split application of urea at rates of 50 kgN ha‐1 at seeding and minimum 25 kgN ha‐1 topdressed at tillering. Of the four methods of N fertilizer placement (broadcast or broadcast and incorporation before seeding, side‐banding at seeding and broadcast two weeks after seeding) maximum yields were obtained either by broadcasting the initial portion of the fertilizer two weeks after seeding, or by broadcast and incorporation prior to seeding.

Testing the Difference between Limiting Yields in Quadratic Fertilizer Response Curves1

AbstractKnowledge on whether or not fertilizer respom curves have the same limiting yield is useful when comparing fertilizers and estimating their availability coefficient. A statistical procedure to test the difference between limiting yields of two quadratic response curves is presented. The test is contingent to the assumption that the estimated nutrient rates corresponding to the limiting yields are constants. Application of the procedure is illustrated when comparing rice (Oryza sativa L.) response to two sulfur‐coated ureas (SCUs) differing in solubility with split application of urea. Only the SCU with lower solubility produced a significantly larger limiting yield than split application of urea.

Time and mode of nitrogen fertilizer application to tropical wetland rice

In experiments with transplanted rice (Oryza sativa L.) at the International Rice Research Institute, Philippines, two methods of split application of urea and ammonium sulfate were compared with deep, point placement (10 cm) of urea supergranules and broadcast application of a slow-release fertilizer sulfur-coated urea (SCU). Comparisons were made in the wet and dry seasons and were based on rice yield and N uptake. Urea- and ammonium-N concentrations and pH of the floodwater were measured to aid interpretation of the results. Split applications of urea were generally less efficient than ammonium sulfate. The split in which the initial fertilizer dose was broadcast and incorporated into the soil before transplanting was more effective than the split in which the fertilizer was broadcast directly into the floodwater 21 days after transplanting. Both split applications were inferior to the urea supergranules and SCU, in terms of both yield and N uptake efficiency; average apparent N recoveries ranged from 30% for the delayed split urea to 80% for the urea supergranule. Broadcast applications of urea and ammonium sulfate produced high floodwater concentrations of urea- and ammonium-N, which fell to zero within 4–5 days. Floodwater pH was as high as 9.3 and fluctuated diurnally due to heavy algal growth. Ammonia volatilization and algal immobilization of N in the floodwater were probably responsible for the poor efficiency of the split applications; the supergranules and SCU on the other hand produced low floodwater N concentrations and were efficiently used by the rice crop.

Comparison of Modified Urea Fertilizers and Estimation of Their Availability Coefficient Using Quadratic Models

AbstractA procedure to compare N fertilizers based on comparing complete response curves simultaneously represented by a quadratic multifertilizer response model (MRM) is discussed. A modified version of the MRM, called fertilizer testing model (FTM), is used to test differences among response curves. The FTM describes the response curve to a fertilizer selected as a standard as well as the additional effect of test fertilizers over the response to the standard. In case of different response curves, an approximate test to decide whether the curves have equal limiting yield is introduced. Finally, a procedure to estimate the availability coefficient from quadratic response curves having equal limiting yield is derived.These procedures were employed to analyze six field experiments conducted over a period of 3 years in Korea using three varieties of rice (Oryza sativa L. ‘Tongil,’ ‘Jinheung,’ and ‘Milyang 23’) and three fertilizers (urea and two sulfur‐coated ureas, or SCU) applied at four or five levels of N. Two out of six experiments showed a significant effect from SCU‐A (25% release/7 days) beyond that of split‐applied urea, whereas SCU‐B (14% release/7 days) showed significant additional effects in three out of five experiments. However, in four of these six experiments, the limiting yield of the response curves of SCU was significantly higher than that of urea, precluding a valid estimation of the availability coefficient. Possibly, the proper combination of N dose and timed release of N from SCU in these experiments translated into grain yields unmatched by split applications of urea.