Effects of nitrogen source,rate and application time on boronia (Boronia megastigma Nees) leaf nitrogen and flower production

Nitrogen was supplied from two fast release sources, ammonium sulfate ((NH₄)₂SO₄) and calcium nitrate (Ca(NO₃)₂) and a slow release source, isobutylidene diurea (IBDU) to boronia, a new flower crop native to Australia. At lower rates (25 kg per ha), N availability from different sources, as indicated by the leaf N concentration, did not differ within a month after application but three months after application, N availability was higher from IBDU than from (NH₄)₂SO₄ or Ca(NO₃)₂. At 50 or 100 kg per ha, N availability was higher throughout the year from (NH₄)₂SO₄ or Ca(NO₃)₂ than from IBDU, thereby allowing luxury consumption and causing toxicity. The flower yield increased with increasing N rates. Complete doses of all N rates which were applied early during the vegetative growth gave the highest yields and the same N rates applied in split doses at different phases of plant growth decreased the yields. In addition, high N availability during flowering (caused by a split dose) further decreased the yield. At all application times, IBDU gave the highest yield and the differences in yields with (NH₄)₂SO₄ and Ca(NO₃)₂ were not significant. The leaf N concentration associated with maximum yield declined as the plant advanced towards flowering.     

Effect of instrument response time on heat release rate measurements

A linear hereditary integral technique provides simple analytic solutions for deconvoluting thermopile and oxygen consumption data to remove the effect of instrument response time on peak and integrated heat release rate values. A comparison of corrected and uncorrected thermopile and oxygen sensor data obtained on an Ohio State University (OSU) apparatus for various materials indicates that significant errors in peak and integrated heat release rate can result from delayed instrument response to repidly changing heat flows. However, correcting for temporal effects alone using this procedure does not account for differences between heat release rate values obtained by thermopile and oxygen consumption methods.     

Relationships between ammonia volatilization and nitrogen fertilizer application rate,intake and excretion of herbage nitrogen by cattle on grazed swards

Grazed pastures emit ammonia (NH₃) into the atmosphere; the size of the NH₃ loss appears to be related to nitrogen (N) application rate.The micrometeorological mass balance method was used to measure NH₃ volatilization from rotationally grazed swards on three plots in the autumn of 1989 and throughout the 1990 growing season. The aim of the research was to derive a mathematical relationship between NH₃ volatilization and N application rate, which would vary between soil type and weather conditions. In both years the plots received a total of 250, 400 or 550 kg N ha^–1 as calcium ammonium nitrate (CAN) split over 6 to 8 dressings. The number of grazing cycles ranged from 7 to 9 for the three N plots.In the last two grazing cycles of 1989, NH₃ losses were 3.8, 12.0 and 14.7 kg N ha^–1 for the 250N, 400N and 550N plots, which was equivalent to 5.3%, 13.9% and 14.4% of the amount of N excreted on the sward, respectively. In 1990, NH₃ losses were 9.1, 27.0 and 32.8 kg N ha^–1 for the 250N, 400N and 550N plots, which was equivalent to 3.3%, 6.9% and 6.9% of the N excreted, respectively. Differences in urine composition between the plots were relatively small. Rainfall and sward management affected the size of the NH₃ volatilization rate. Volatilization of NH₃ was related to N excretion and N application rate.A calculation procedure is given to enable the estimation of NH₃ volatilization from N application rate. Adjustments can be made for grazing efficiency, grazing selectivity, N retention in milk and liveweight gain, concentrate N intake and milking duration. Losses of NH₃ increase progressively with an increase in N application rate until herbage yield reaches a maximum at an application rate of about 500 kg N ha^–1 yr^–1.     

The effect of urea pellet size and rate of application on ammonia volatilization and soil nitrogen dynamics

In a field experiment on deep, yellow, sandy soil near Badgingarra, Western Australia, the residual value of superphosphate applied one and two years previously was measured relative to freshly-applied superphosphate using yields of narrow-leafed lupin (Lupinus angustifolius), barley and wheat. In addition, soil samples were collected for measurement of bicarbonate-extractable soil P. This was also used to estimate the residual value of the superphosphate.For lupins and wheat, and for bicarbonate-extractable soil P, the residual value decreased with increasing level of application. For barley grain, the residual value was not significantly affected by the level of application.The decrease in residual value of superphosphate with increasing level of application is attributed to increased leaching of applied phosphorus (P) down the profile of the sandy soils as the level of application increases. This may reduce subsequent plant yields due to the delay in seedling roots reaching the P in the soil during the crucial early stages of plant growth.For lupins, the relationship between yield and the level of superphosphate applied was markedly sigmoidal. The relationship for wheat and barley was exponential. Consequently, at suboptimal levels of P application, lupins required about two to three times more P than wheat or barley to produce the same yield. However, lupins required less P to achieve near-maximum yield.     

Effect of level,timing and method of nitrogen application on spring-planted sugarcane

A field experiment conducted at the Indian Agricultural Research Institute, New Delhi during the years 1976–79 involving two planted cane crops and two ratoons showed that nitrogen application to planted cane increased the millable cane and sugar yields of the planted cane and had a significant residual effect on the ratoon. Taking together the yields of planted cane and ratoon, an application of 150 kg N ha^–1 increased the yield of millable cane by 33.3t ha^–1 and that of sugar by 3.9t ha^–1. The results suggested that with 75 kg N ha^–1 three-quarters should be applied at planting, while with 150 kg N ha^–1 only half should be applied at planting. The remaining dose of nitrogen should be applied at earthing up. Foliar application of part of the nitrogen indicated some advantage in the case of millable canes in the planted cane, but this did not show up in the sugar yield.     

Growth response,yield and yield components of upland cotton (Gossypium hirsutum L) as affected by rates and time of nitrogen application in the Nigerian savannah

Effects of rate and time of nitrogen fertilization on growth, yield and yield components of upland cotton (Gossypium hirsutum L) were studied in two years (1975–76). Four rates of nitrogen application (0, 26, 52 and 78 kg ha^–1) timed at 3 or 8 weeks after sowing were compared. Seed cotton yield components increased significantly with increased N application at least up to 52 kg N ha^–1, with yield increases between 49% and 73%. Seed cotton yield was influenced by treatments mainly through boll number. Both crop growth rate and fruiting were enhanced by nitrogen fertilization. Applying N at 8 weeks (flowering) favoured yield only slightly over that at 3 weeks (thinning), but improved crop growth and fruiting by about 64% and 24%, respectively. There were significant N rate × time interactions in favour of fertilization at flowering. Applying 52 kg N ha^–1 at 8 weeks seems best for cotton in the Nigerian savannah.     

Influence of pH,time and rate of application on phosphate rock dissolution and availability to pastures

Soil Samples were collected from a field experiment conducted to evaluate the agronomic effectiveness of a reactive phosphate rock (PR), Sechura sand, relative to that of monocalcium phosphate (MCP) at different soil pHs and rates of application. The samples were analysed for P soluble in the soil solution and bicarbonate extractable P. The rate of dissolution of PR was calculated from the data on the fractionation of inorganic P. In MCP plots P in the soil solution decreased sharply with time especially at low pHs and high rates of fertiliser application. In PR plots the concentration remained with time at the same as or a slightly higher level than that was found one month after application. Solution concentration of P was lower at very high rates of PR application than at intermediate rates. In both MCP and PR plots bicarbonate extractable P decreased with increasing pH. Bicarbonate extractable P was linearly related to MCP but not to PR applied. The rate of dissolution and the proportion of PR dissolved decreased with increasing rates of PR application but the amount dissolved increased. Phosphate dissolved at high level of PR application did not seem to enhance proportionately either the concentration of P in soil solution or bicarbonate extractable P.     

Influence of pH,time and rate of application on phosphate rock dissolution and availability to pastures

The agronomic effectiveness of an unground reactive phosphate rock from Sechura, Peru, was compared with that of monocalcium phosphate in a severely P deficient and highly P retentive soil (vitrandept) over a period of three years. Soil pHs were adjusted to pH 5.1, 5.3, 5.6 and 6.4. The sward consisted mostly of ryegrass (Lolium perenne) and white clover (Trifolium repens). Fertilisers were applied at six rates at pH 5.3 and three rates at other pHs in the first year. For two of the rates fertilisers were reapplied in the second year. Dry matter yields, P uptake and ground cover of clover were determined during the experimental period. In phosphate rock treated plots a negative linear relationship was obtained between soil pH and the logarithm of yield. The agronomic effectiveness of phosphate rock relative to monocalcium phosphate increased with time at all pHs. Calculated at fertiliser rates which produced near maximum yields, relative agronomic effectiveness at soil pHs 5.1, 5.3, 5.6 and 6.4 were respectively 58, 60, 18, and 5 in year one; 118, 125, 77 and 38 in year three. At pH 5.3, as the rate of application increased the relative agronomic effectiveness of the phosphate rock generally decreased in year one but was enhanced in the intermediate rates in years two and three. The data for ground cover of clover gave a similar trend to that for herbage yield and P uptake.     

The influence of rate and time of nitrate supply on nitrogen fixation and yield in pea (Pisum sativum L.)

The influence of nitrate N supply on dry matter production, N content and symbiotic nitrogen fixation in soil-grown pea (Pisum sativum L.) was studied in a pot experiment by means of¹⁵N fertilizer dilution. In pea receiving no fertilizer N symbiotic nitrogen fixation, soil and seed-borne N contributed with 82, 13 and 5% of total plant N, respectively. The supply of low rates of nitrate fertilizer at sowing (starter N) increased the vegetative dry matter production, but not the seed yield significantly. Nitrogen fixation was not significantly decreased by the lower rates of nitrate but higher rates supplied at sowing reduced the nitrogen fixation considerably. Applying nitrate N at the flat pod growth stage increased the yield of seed dry matter and N about 30% compared to pea receiving no nitrate fertilizer. Symbiotic nitrogen fixation was reduced only about 11%, compared with unfertilized pea, by the lowest rate of nitrate at this application time. The pea very efficiently took up and assimilated the nitrate N supplied. The average fertilizer N recovery was 82%. The later the N was supplied the more efficiently it was recovered. When nitrate was supplied at the flat pod growth stage 88% was recovered, and 90% of this N was located in the seeds.     

Influence of source, time and method of application, and simulated rainfall on recovery of nitrogen fertilizers applied to bromegrass

Four field experiments were conducted in central Alberta to determine influence of the N source, time and method of application and simulated rainfall on the recovery of¹⁵N-labelled fertilizers applied to meadow bromegrass (Bromus biebersteinii Roem and Shultz. cv. Regar) in plants (topgrowth plus roots) and in soil. The first experiment compared two N sources (urea and ammonium nitrate (A.N.)) and six times of application (early fall, late fall, early winter, early spring, late spring and spring-summer split) where N fertilizers were surface-broadcast. Urea gave lower N recovery than A.N., regardless of time of application (on the average by 16.4% in plants and by 18.3% in plants plus soil). For urea, early spring application gave higher N recovery than the other times of application, especially at the Eckville site. For A.N., spring applications gave higher N recovery than fall or early winter applications but N recovery was only slightly greater with early spring than late spring application. The second experiment evaluated methods of N placement (surface-broadcasting and banding). The N recovery in plants increased with subsurface band placement over surface-broadcast by 20.2% for fall application and by 15.5% for spring application. The other two experiments investigated the effect of amount (0, 5, 10, 20 and 40 mm) of simulated rainfall and interval (0, 1, 2, 4, 8, and 16 d) between surface urea application and simulated rainfall on N recovery. Simulated rainfall of 10 mm immediately after surface urea application on moist soil increased the N recovery in plants by 8.1–10.7% compared to no simulated rainfall. Delaying simulated rainfall (20 mm) by 4 d after surface urea application decreased the N recovery in plants by 8.7–15.2%. In conclusion, the N recovery improved greatly when urea was placed below the soil surface or with simulated rainfall immediately after surface urea application.     

Effect of the timing and rate of nitrogen fertilization on the growth and recovery of fertilizer nitrogen within the potato (Solanum tuberosum L.) crop

The effect of the timing of N fertilizer application on the uptake and partitioning of N within the crop and the yield of tubers has been studied in two experiments. In 1985 either none, 8 or 12 g N m^–2 was applied and in 1986 none, 12 or 18 g N m^–2. Fertilizer N was applied either at planting, around the time of tuber initiation or half at planting and the remainder in four foliar sprays of urea during tuber bulking.¹⁵N-labelled fertilizer was applied to measure the recovery of fertilizer N in the crops.There was an apparent pre-emergence loss of nitrate from the soil when N was applied at planting in 1986, thereby reducing the efficiency of fertilizer use. Applying the N at tuber initiation delayed and reduced the accumulation of N in the canopy compared with crops receiving all their fertilizer at planting. Foliar sprays of urea slightly increased both tuber yields and tuber N contents when compared to a single application at planting. The proportion of the fertilizer N recovered in the crop was little affected by the rate of N application, but a greater proportion of foliar-applied N was recovered than N broadcast at planting, due partly to pre-emergence losses of nitrate in 1986. It is suggested that late applications of N was foliar sprays can be of benefit to crops with a long growing season and reduce environmental losses of N.     

免疫后时间及流行强度对1剂次水痘疫苗效力的影响

目的探讨免疫后时间及流行强度对接种1剂水痘疫苗效力的影响。方法对广州市天河区2011年1⁶月发病的16月发病的1¹5岁水痘病例,采用1︰1配对的病例对照研究方法,对不同年龄、处在不同流行强度时的1剂次水痘疫苗效力(vaccine effectiveness)进行分析,并评价两者对疫苗效力的影响。结果调查601病例/对照对子,总的疫苗效力为70.33%(95%CI:60.42%15岁水痘病例,采用1︰1配对的病例对照研究方法,对不同年龄、处在不同流行强度时的1剂次水痘疫苗效力(vaccine effectiveness)进行分析,并评价两者对疫苗效力的影响。结果调查601病例/对照对子,总的疫苗效力为70.33%(95%CI:60.42%⁷7.76%,P<0.01),1岁组疫苗效力为90%(95%CI:65.27%77.76%,P<0.01),1岁组疫苗效力为90%(95%CI:65.27%⁹7.12%,P<0.01),随年龄增长,疫苗效力呈下降趋势(χ2趋势=12.68,P<0.01),≥10岁组病例与对照暴露率差异无统计学意义(P>0.05),疫苗基本失去保护效力。集体单位297.12%,P<0.01),随年龄增长,疫苗效力呈下降趋势(χ2趋势=12.68,P<0.01),≥10岁组病例与对照暴露率差异无统计学意义(P>0.05),疫苗基本失去保护效力。集体单位2¹5岁病例511对子疫苗效力为66.67%(95%CI:54.52%15岁病例511对子疫苗效力为66.67%(95%CI:54.52%⁷5.57%,P<0.01),水痘罹患率越高,疫苗效力越低,罹患率在15%以上时,疫苗效力差异无统计学意义(P>0.05),疫苗基本失去保护效力。结论接种1剂水痘疫苗约10%初次免疫失败;免疫后时间及流行强度对疫苗效力均有明显影响,后者影响更大。若将1剂免疫程序改为2剂免疫程序,对控制儿童水痘暴发将具有重要意义。     

Effect of short thermal treatment on cotton degradation

Cotton fabric was subjected to thermal treatment for durations ranging from 0.5 to 5 min at a temperature range of 160°C. In comparison with the untreated cotton, the copper number (measure of the aldehyde content) decreased after heating cotton for up to 3 min at 160°, 180°, and 190°C but increased when heating was prolonged to 5 min. Thermal treatment at 200°C or above caused an appreciable increase in the copper number. The carboxyl content increased with time of heating, attained a maximum, and then fell down to reach values which in some cases were lower than that of untreated cotton. Thermal treatment at 180°C caused a substantial reduction in the D. P.; this reduction increased with time of treatment. At the other temperatures there was no significant decrease in D. P. when cotton was heated up to 3 min. The D. P. decreased in these cases only when the thermal treatment was conducted for 5 min. The tensile strength remained practically unimpaired after thermal treatment of the cotton for up to 2 min, regardless of the temperature used within the range studied. A loss in tensile strength of ca. 9% and 13% was observed with fabrics treated for 5 min at 160° and 180°C, respectively. This contrasts with a loss of ca. 4% at 190°C, 7% at 200°C, and 8% at 220°C. The highest dye exhaustion was obtained on cotton which was thermally treated at 180°C prior to dyeing, while the lowest dye exhaustion was obtained on cotton heated at 220°C. Thermal treatment at 160°C left the susceptibility of cotton toward the dyestuff practically unaltered.     

碳氮比与氨氮负荷对序批式活性污泥法同步硝化反硝化的影响

为了提高生物脱氮的效率,研究采用序批式活性污泥法(SBR工艺)考察碳氮质量比w(C/N)与氨氮负荷对同步硝化反硝化的影响。结果表明:当w(C/N)为5.6,氨氮负荷为0.024 g/(g.d),碳源快速消耗,SBR工艺较难实现同步硝化反硝化,同步硝化反硝化率只能够达到0.76%。当w(C/N)为10.5,氨氮负荷为0.024 g/(g.d)时,SBR系统能够实现同步硝化反硝化,同步硝化反硝化率达到97.6%,NH4+-N和COD去除率均接近100%;当w(C/N)为16.3,氨氮负荷为0.024 g/(g.d)时,同步硝化反硝化率为94.5%,增加外加碳源的成本。同步硝化反硝化可以取代二段独立的硝化和反硝化过程,节省运行费用。     

供氧速率影响同时硝化反硝化脱氮的研究

通过在实验室内建立同时硝化反硝化(SND)装置,考察了供氧速率对SND脱氮的影响。结果显示,当供氧速率由50 m L/(min·L)提高至100 m L/(min·L)时,COD与NH3-N去除效率变化不大,分别保持在96%与99%以上,而TN去除率由80%降低至70%左右。为研究造成脱氮性能差异的原因,采用批次试验测试了不同供氧速率下的脱氮过程。研究结果表明,供氧速率的增加不影响反硝化速率,但会提高碳氧化速率,从而加快有机物的消耗,缩短了反硝化的时间,从而造成TN去除率下降。     

Nitrogen rate impacts on tropical maize nitrogen use efficiency and soil nitrogen depletion in eastern and southern Africa

Nutrient Cycling in Agroecosystems - Sub-Saharan Africa is facing food security challenges due, in part, to decades of soil nitrogen (N) depletion. Applying N fertilizer could increase crop yields...     

Effects of nitrification inhibitors and time and rate of slurry and fertilizer N application on silage maize yield and losses to the environment

Field experiments with silage maize during eight years on a sandy soil in The Netherlands, showed that dicyandiamide (DCD) addition to autumn-applied cattle slurry retarded nitrification, thus reducing nitrate losses during winter. Spring-applied slurry without DCD, however, was on average associated with even lower losses and higher maize dry matter yields.Economically optimum supplies of mineral N in the upper 0.6 m soil layer in spring (EOSMN), amounted to 130–220 kg ha^–1. Year to year variation of EOSMN could not be attributed to crop demand only. According to balance sheet calculations on control plots, apparent N mineralization between years varied from 0.36 to 0.94 kg ha^–1 d^–1. On average, forty percent of the soil mineral N (SMN) supply in spring, was lost during the growing season. Hence, the amounts of residual soil mineral N (RSMN) were lower than expected. Multiple regression with SMN in spring, N crop uptake and cumulative rainfall as explanatory variables, could account for 79 percent of the variation in RSMN.Postponement of slurry applications to spring and limiting N inputs to economically optimum rates, were insufficient measures to keep the nitrate concentration in groundwater below the EC level for drinking water.     

Influence of cultivars and nitrogen rates on the residual effects of potassium applications to preceding cotton on maize

The long-term residual effects of K application rates and cultivars for preceding cotton (Gossypium hirsutum L.) on subsequent maize (Zea mays L.) and the influence of N rates applied to preceding cotton and to maize on the residual K effects were examined on maize under no-tillage in the United States. Two field experiments were conducted on a no-till Loring silt loam at Jackson, TN during 1995–2008 with N rates (90 and 179 kg ha^?1) × K rates (28, 56, and 84 kg ha^?1) and cotton cultivars (determinate and indeterminate) × K rates (56 and 112 kg ha^?1) as the treatments, respectively, in the preceding cotton seasons. Maize was planted under no-tillage on the preceding cotton experiments without any K application during 2009 through 2011. The residual effects of K rates applied to preceding cotton on soil K levels were significantly influenced by the N rates applied to preceding cotton and to maize when the data were combined from 2008 to 2011. Relative to the standard N management practices of 168 kg N ha^?1 for maize and 90 kg N ha^?1 for preceding cotton, the higher N application rate 269 kg N ha^?1 to maize and 179 kg N ha^?1 to preceding cotton reduced the residual effects of K rates on soil K. However, cultivar for preceding cotton did not affect the residual effects of K fertilizer on soil K fertility, leaf K nutrition, plant growth, or grain yield of subsequent maize on a high K field.     

Effect of lime nitrogen on the efficiency of urea and other ammonium nitrogen fertilizers

Five pot experiments were conducted with wheat and rice in a net house to study the effect of lime nitrogen (LN, contains about 55% calcium cyanamide) amendment rates on the efficiency of urea, the recovery urea-¹⁵N, the efficiency of the three nitrogen fertilizers(NF), on the efficiency of urea in the three soils, and on NO ₃ ^- -N leaching from a flooded soil. A rate of LN-N of 5–8% of applied fertilizer N increased the recovery of labeled urea-N by 9.42%. The effect of LN on the efficiency of NF was urea > ammonium sulfate > ammonium chloride. Under flooded conditions, LN decreased NO ₃ ^- formation and leaching.Responses of several crops to LN amended fertilizers were also studied in field experiments. At equal NPK applications, the efficiency of basal applications to rice, wheat, corn, potatoes, soybean, peanut, grapes, peaches, melon and watermelon were bette r with LN than without. Efficiency with a basal fertilizer for rice or wheat with LN were the same as with the same fertilizer without LN applied in split applications.     

Assessing internal crop nitrogen use efficiency in high-yielding irrigated cotton

Improving the efficiency of nitrogen (N) fertiliser use is one means of reducing greenhouse gas emissions, particularly in irrigated crops such as cotton (Gossypium hirsutum L.). Internal crop N use efficiency (iNUE) was measured within two N fertiliser rate experiments that covered a wide range of N fertility over six cropping seasons. Crop iNUE was determined by dividing lint yield by crop N uptake. No nutrients other than N limited cotton growth or yield and the crops were irrigated to avoid drought stress. The optimal N fertiliser rates were determined from fitted quadratic functions that related lint yields with N fertiliser rates for each cropping system in each year. When the optimal N fertiliser rate was applied, crop iNUE averaged 12.5 ± 0.2 kg lint/kg crop N uptake. The crop iNUE was then used to determine the degree to which N fertiliser was under or over-applied, with respect to the economic optimum N fertiliser rate. Low iNUE values were associated with excessive N fertiliser application. Crop iNUE was determined in 82 commercial cotton crops in six valleys over the final 4 years of this study. The crop iNUE value was high in 8 fields (10%), optimal in 9 fields (11%) and low in 65 fields (79%). Crop N uptake averaged 247 kg N/ha, yield 2,273 kg lint/ha and crop iNUE 10.1 kg lint/kg crop N uptake for these sites. Averaged over all sites and years, about 49 kg N/ha too much N fertiliser was applied. Apparent N fertiliser recovery by cotton in the N rate experiments ranged from <20% in N-fertile treatments where legume crops had been grown, to more than 60% following winter cereal crops. Information on crop iNUE will enable cotton producers to assess their N fertiliser management and adjust N fertiliser rates for future crops. This study has demonstrated that there is scope to substantially reduce N fertiliser inputs to Australian cotton fields without reducing yields.