Effects of Slow-release Nitrogen Fertilizer on Yield and Nitrogen Accumulation of Summer Maize in Shajiang Black Soil Area

[Objectives] This study was conducted to verify the field application effect of slow-release nitrogen fertilizer on summer maize in Shajiang black soil area by simultaneous sowing and fertilization, and explore the application scope and nitrogen metabolism mechanism, so as to lay a foundation for fertilizer reduction and efficiency improvement. [Methods] With maize variety Beiqing 340 and sulfur-coated urea as experimental materials, five nitrogen application levels were set, namely, control (C0), slow-release nitrogen 70 kg/hm^(2) (C70), slow-release nitrogen 140 kg/hm^(2) (C140), slow-release nitrogen 210 kg/hm^(2) (C210) and slow-release nitrogen 280 kg/hm^(2) (C280). The phosphorus and potassium fertilizers were all in accordance with the unified standard. [Results] With the application rate of slow-release nitrogen increasing, the nitrogen accumulation in organs increased first and then decreased after tasseling stage of maize. In order to reduce the fertilizing amount and increase efficiency, 210 kg/hm^(2) of slow-release nitrogen fertilizer was the best fertilizing amount for summer maize in Shajiang black soil area. [Conclusions] This study provides reference for fertilizer reduction, efficiency improvement and sustainable development of summer maize in Shajiang black soil area.

Effects of nitrogen fertilizer on protein synthesis, accumulation, and physicochemical properties in common buckwheat

Nitrogen(N)fertilization affects grain quality in common buckwheat(Fagopyrum esculentum Moench).But the effects of N fertilizer on various buckwheat protein parameters are not fully understood.This study aimed to investigate the synthesis,accumulation,and quality of buckwheat protein under four N application rates in the Loess Plateau,China.Optimal N application(180 kg N ha-1)improved yield,agronomic traits,and N transport and increased protein yield and protein component accumulation.Prolamin and glutelin accumulation first increased and then decreased with increasing N application.The relationships between the contents of protein components and the amount of applied N generally followed quadratic functions.Nitrate reductase and glutamine synthetase activities first increased and then decreased with increasing N levels.Optimal N fertilizer increased the waterholding capacity and thermal stability of buckwheat protein and reduced its emulsification capacity,but negligibly changed its oil-absorption capacity.Hydrophobic amino acids and glutelin content were the main factors affecting protein quality.

Yield of Roselle (Hibiscus sabdariffa L.) as Influenced by Manure and Nitrogen Fertilizer Application

Field experiments were carried out on roselle (Hibiscus sabdariffa L) during the 2019 and 2020 cropping seasons at the CSIR-SARI Research Station at Manga in the Upper East Region of Ghana. The aim of the experiment was to study the response of roselle to cowdung, nitrogen fertilizer and their interaction on the growth and yield of roselle. The treatments consisted of factorial combination of five rates of cowdung (0, 1.5, 2.5, 3.5 and 4.5 t/ha) and five levels of nitrogen (0, 20, 40, 60 and 80 kgN/ha) laid out in a randomized complete block design and replicated three times. Data were collected on days to 50% flowering, plant height, number of leaves per plant and dry calyx yield. The results indicated that differences in dry calyx yield due to the manure and nitrogen fertilizer effects were highly significant (P 0.01). Application rate of 2.5 t/ha manure recorded the highest yield of 340 kg/ha and 308.1 kg/ha in 2019 and 2020 respectively. Increasing manure rate from 2.5 - 3.5 t/ha did not result in significant increases in dry calyx yield. The four rates differed significantly from the control which had the least calyx yield of 190.3 kg/ha and 180 kg/ha in 2019 and 2020 respectively. Nitrogen rate of 60 kg/ha recorded the highest dry calyx yield of 510.5 kg/ha and 370.4 kg/ha in 2019 and 2020 respectively which were significantly different from calyx yields recorded by other treatments. The trend on partial budget analysis was consistent in both seasons with the highest yielding treatments (2.5 t/ha cowdung manure and 60 kg/ha) recording the highest net benefit while the control (0 kg/ha) ranked last. The application rate of 2.5 t/ha of cowdung and 60 kg/ha of Nitrogen is thus recommended for optimum roselle production and productivity in the study area.

Effects of Combined Application of Biochar-based Organic Fertilizer and Reduced Nitrogen Fertilizer on Soil Enzyme Activity and Yield of Purple Cabbage(Brassica oleracea var.capita rubra)in Yuanmou County

[Objectives]In response to the issue of soil improvement in Yuanmou County,the effects of combined application of biochar-based organic fertilizer and reduced nitrogen fertilizer on soil nutrients,soil enzyme activity,and yield of purple cabbage(Brassica oleracea var.capita rubra)were investigated in the field base of Institute of Thermal Zone Ecological Agriculture,Yunnan Academy of Agricultural Sciences in Yuanmou County.[Methods]A total of 13 treatments were set up by applying biochar-based organic fertilizer at three levels of 15,30 and 45 t/hm^(2)(T_(1),T_(2),T_(3)),combined with top application of nitrogen fertilizer(urea)at four levels:375(N_1),300(N_(2)),225(N_(3))and 0 kg/hm^(2),with non-fertilizing treatment as control check(CK),in order to explore the optimal ratio for the combined application of biochar-based organic fertilizer with nitrogen fertilizer.[Results]The application of biochar-based organic fertilizer could significantly improve soil nutrients,enzyme activity,and purple cabbage yield.The improvement effect of combined application with nitrogen fertilizer was higher than that of single application of biochar-based organic fertilizer,and the improvement effect was enhanced with the application amount of biochar-based organic fertilizer increasing.The contents of organic matter and total nitrogen were the highest in treatment T_(3)N_(3),of which the values increased by 81.39%and 56.09%compared with the CK,respectively.The contents of soil hydrolyzable nitrogen,available phosphorus,and available potassium were all the highest under treatment T_(3)N_(2),with increases of 92.76%,171.01%and 235.50%,respectively.There was a significant positive correlation between the activity of soil catalase,urease,and sucrase and organic matter,total nitrogen,and available nutrients.The overall soil enzyme activity was relatively higher in treatment T_(3)N_(2).The yield of purple cabbage treated with biochar-based organic fertilizer combined with nitrogen fertilizer could reach 85750 kg/hm^(2),which was 94.78%higher than that treated with biochar-based organic fertilizer alone.Based on comprehensive analysis,the optimal combination ratio was 45 t/hm^(2)of biochar-based organic fertilizer and 300 kg/hm^(2)of urea(T_(3)N_(2)).[Conclusions]This study provides data support for the promotion of biochar-based organic fertilizers and reduced fertilizer in agricultural soil in the Dam area of Yuanmou County.

Nitrogen recovery and nitrate leaching of controlled release nitrogen fertilizer in irrigated paddy soil

Ordinary high nitrogen fertilizer often results in nitrate (NO3--N) leaching and low recovery. Microplot and field plot experiments were conducted to determine the effect of controlled release nitrogen fertilizer (CRNF) on reco very and nitrate leaching on paddy soils. During two early rice cropping seasons (2002 and 2003), a single basal application of CRNF at 90 kg N ha-1 increased grain yields by 7.7%to 11.6%compared with two applications of urea. Estimated by the difference method fertilizer N recovery of CRNF (mean 76.3%) was 38.9 pe rcentage point higher than that of urea (mean 37.4%); estimated by 15N isotope method (mean 49.6%) CRNF (mean 67.1%) was 35.9 percentage point higher than ur ea (mean 31.2%). NO3--N leaching losses were 9.19 and 6.70 kg ha-1 for urea and CRNF, respectively. NO3--N leaching during the early rice cropping season was 27.1 %lower from CRNF than from two applications of urea. These losses repr esent 10.2%and 7.4%of applied urea-N and CRNF-N. Results from this study ind icate that CRNF improves N recovery and reduces NO3--N leaching and increases rice yield.

Effects of Nitrogen Fertilizer Application Mode on Sugarcane Yield and Soil Nutrient Change

[Objective] The aim was to improve use ratio of N fertilizer in sugarcane production and reduce N pol ution in agricultural production. [Method] With ROC22 as materials, N fertilizer quantities were set, including 38, 276 and 414 kg N/hm2, according to three fertilization approaches （approach 1： N fertilizer at 10% as base fertilizer, 30% N fertilizer applied to soil dressing, 60% N fertilizer applied to big ridging; approach 2： 30% N fertilizer as base fertilizer, 70% N fertilizer applied to soil dressing; approach 3： 100% N fertilizer as base fertilizer）. Some sugarcane in-dices, such as agronomic traits, yield and soil nutrients, were measured to research the relationship of N fertilizer with sugarcane growth and soil nutrients. [Result] Sug-arcane yield was increasing upon N fertilizer and reached the peak with N fertilizer at 276 kg N/hm2. In addition, early application of N fertilizer would promote sugar-cane jointing, growth and increase sugarcane yield. Nitrogen and available K con-tents were increasing upon N fertilizer, but excessive N fertilizer also caused soil acidification. N fertilizer applied early could help dissolve soil phosphate and improve phosphorus absorption and utilization. Applying N fertilizer completely as base fertil-izer was likely to cause N loss and low use efficiency. [Conclusion] The appropriate application mode for sugarcane is to apply N fertilizer twice at 138-276 kg N/hm^2.

Effects of the Application of Controlled Release Nitrogen Fertilizer on Rapeseed Yield, Agronomic Characters and Soil Fertility

In order to study the effects of controlled release nitrogen fertilizer （CRNF） application on rapeseed, a simulated experiment was carried out with 3 types of paddy soils in Dongting Lake area for 4 consecutive years of applying CRNF under double rice cropping system after planting rapeseed crop in the fallow season. The effects of CRNF application on rapeseed yield, agronomic characters and soil fertility were studied in this paper. The results showed that CRNF application improved the growth of rapeseed plant and increased rapeseed yield of CRNF treatments in the purple calcareous clayed paddy soil （PCS） and alluvial loamy paddy soil （ALS） which respectively increased by 12.2% and 9.8% compared with applying urea, re- spectively. The rapeseed yield in 70% CRNF treatment obviously decreased com- pared with urea treatment. The contents of available N and organic carbon in soil increased by 25.0% and 3.2% in CRNF treatment in the ALS after rapeseed crop, respectively; and available N increased by 13.5% in the PCS. Both rapeseed yield and soil fertility in CRNF treatment and 70% CRNF treatment were lower than those in CK treatment in the reddish yellow clayed paddy soil （RYS）. The results al- so indicated that the functions of CRNF application on rapeseed yield increase and soil nitrogen fertility improvement were very obvious in the PCS and ALS.

Effects of Panicle Fertilizer Application on Source-Sink Characteristics and Nitrogen Fertilizer Use Efficacy of Ganxin688

[Objective]The paper was to explore the effect of postponing application of N fertilizer on source-sink characteristics of super hybrid rice Ganxin688.[Method] With super hybrid rice Ganxin688 as test material,the source organ traits（leaf area index,leaf weight,chlorophyll content,photosynthetic rate of flag leaf,stem and sheath dry matter accumulation and output） and yield were measured,the effects of nitrogen application on source-sink relationship,yield and N fertilizer use efficiency were also studied.[Result] Appropriate postponing of N fertilizer was benefit for optimizing population quality,harmonizing source-sink relation,enhancing leaf function,prolonging leaf function period and increasing N fertilizer use efficiency.After heading,the leaves area index（LAI） and chlorophyll content increased with the increasing application amount of panicle fertilizer,and their reduction rate slowed down with the increased application amount of panicle fertilizer.Appropriate increased application of panicle fertilizer could prolong the function period of leaves in lower position,increase storage amount of stem and sheath matter,total sink capacity and sink capacity per unit leaf area during heading stage,improve panicle rate and seed setting rate,reduce the demand of grain sink on stem and sheath matter,and increase lodging resistance of plant,which could also increase dry matter productivity and rice productivity of N fertilizer,and increase absorption and application ratio and total accumulation amount of N fertilizer.For Ganxin 688,when N application amount was 175-205 kg/hm2,the proportion of panicle fertilizer in total nitrogen application should be better as 40%-45%.[Conclusion] The study provided basis for making reasonable and efficient N application strategy to establish a coordinated huge sink and strong source relationship for super rice.

Effect of Continuous Application of Controlled Release Nitrogen Fertilizer in Various Types of Soil in Dong-Ting Lake Region under Double Rice Cropping System

[Objective] This study aimed to explore the effects of continuous application of controlled release nitrogen fertilizer under double rice cropping system. [Method] By modeling three types of paddy soils in Dong-Ting Lake area, four treatments as no fertilizer （CK）, urea, controlled release nitrogen fertilizer （CRNF） and 70% controlled release nitrogen fertilizer （70% CRNF） were designed in the micro-plot trials from 2005 to 2008. [Result] The rice yield in treatment CRNF at N 150 kg/hm2 was increased by 10.3%, 8.0% and 2.4% compared with treatment of urea, in alluvial sandy loamy paddy soil （ALS）, purple calcareous clayey paddy soil （PCS）, and reddish yellow loamy paddy soil （RYS）, respectively; and the yield in treatment of 70% CRNF was increased by 6.1%, 2.6% and -0.8%, respectively. The ranking order of nitrogen uptake amount by plant in early rice and late rice was CRNF 70% CRNF urea CK in all three types of soil. Nitrogen utilization efficiency of CRNF in above three types of soil was 60.7%, 59.6% and 56.3%, increased by 23.8%, 19.4% and 16.3% compared with that in treatment of urea, respectively. Nitrogen utilization efficiency of CRNF in early rice was increased year by year, and was higher than that of 70% CRNF during the whole experiment stage, while that in late rice was increased first and then decreased from the 3rd year. [Conclusion] Continuous application CRNF could alleviate the decreasing of soil nitrogen fertility and organic carbon especially in ALS, increase rice yield and nitrogen utilization efficiency in double-rice cropping system.

Effects of Soil Nitrate Nitrogen Residues and Leaching for Different Kinds of Slow-release Nitrogen Fertilizers in Tall-fescue Soil

ObjectiveThe aim was to explore the movement of nitrate nitrogen in tall-fescue soils by different kinds of slow release nitrogen fertilizers. MethodBased on infiltration-tanks and test plots, a new and environment friendly fertilizer was explored. ResultThe results show that compared with urea treatment, slow-release nitrogen fertilizer treatments could reduce nitrate nitrogen content and leaching amount in soils. Compared with PCU30 and IU treatments, the PCU60 treatment became more efficient in reducing nitrate content and leaching amount in 0-90 cm soil layer. ConclusionIn summary, slow-release nitrogen fertilizer, which can reduce soil nitrate content and leaching losses, is a kind of novel fertilizer with high environmental benefit and promising application.

Application Effect of Water-absorbent Slow Release Nitrogen Fertilizer in Latosol

[Objective] A new-type water-absorbent slow release nitrogen fertilizer（WASRNF） was produced through polymerization reaction. Its physicochemical property and application effect in latosol were studied. Feasibility of using WASRNF to improve the serious problems of latosol in rubber planting area in Hainan Island including vulnerable nutrient, free-running fertilizer and water was studied. [Result] The results showed that raw materials of WASRNF, urea and water-retention material formed co-polymer through hydrogen-bond interaction that the WASRNF contained many hydrophilic groups. The p H value of WASRNF is near neutral and its water absorbent rate in tap water could reach 167.17 g·g-1. The water absorbent rates in latosol leach liquors with water/soil ratios of 1：5, 1：10 and 1：20 were 104.66, 122.93 and 145.38 g·g^-1, respectively. The maximum water holding ratio of latosol increased by 23.72%, 30.89% and 39.68% when 0.5%, 1% and 2% WASRNFs were added to latosol, and water evaporation rate of latosol decreased efficiently. Compared with common urea, WASRNF could slow down the leaching rate of nitrogen and the initial leaching amount was only 22.17% of the total amount. [Conclusion]The results indicated that WASRNF in latosol had strong water absorption and water-retention abilities in addition to the good slow release effect, and could efficiently decrease nutrient loss, increase utilization ratio of water and fertilizer and promote interaction between water and fertilizer.

Effects of Nitrogen Fertilizer on Rhizosphere Microbial Populations under Cotton Intercropped with Red Date in Arid Desert Oasis of Southern Xinjiang

[Objective]This study aimed to determine the number of microorganisms of cotton rhizosphere in a soil at various amounts of applied nitrogen fertilizer in a red date-cotton intercropping system. [Method] In the field experiment, nitrogen fer-tilizer was applied at 0, 150, 300, 450, 600, and 750 kg/hm2, respectively. The dy-namic changes of the populations of bacteria, fungi and actinomycetes at the rhizo-sphere of cotton intercropped with red date were investigated. [Result] Microbial populations significantly increased at nitrogen fertilizer of 300 and 450 kg/hm2 during bud, flowering and bol opening periods. The numbers of bacteria and actinomycetes were higher during flowering and bol opening stages than at bud stage. The num-ber of fungi slightly changed during the entire growth period. Appropriate amount of nitrogen fertilizer （300 to 600 kg/hm2） was favorable to the survival of the microor-ganisms in the soil under the intercropping system. [Conclusion] The study provides a guideline for screening and determining the optimum amount of applied nitrogen fertilizer.

Effects of Growing of Different Types of Crops on Constitution of Soil Available Nitrogen and Conversion and Utilization of Nitrogen Fertilizer

The soybean, cotton, maize and sorghum were planted in pot under low nitrogen, high nitrogen treatments, the soil available nitrogen constitution and con- version and utilization of nitrogen fertilizer were determined, so as to provide techni- cal guidance for reasonable use and improving use efficiency of nitrogen fertilizer for different types of crops. Compared with the control with nitrogen but unplanted crop, growing soybean, cotton, maize, sorghum significantly decreased the soil available N contents by 53. 48%, 51.54%, 33.10%, 55.03%,and influenced the constitution of soil available N. Thereinto, growing soybean, cotton, maize and sorghum significantly decreased soil inorganic N contents by 85.41%, 83.09%, 70.89% and 83.35%,but increased soil hydrolysable organic N contents by 1.41, 1.53, 2.11 and 1.28 times, respectively; growing soybean, cotton, maize and sorghum significantly decreased the rate of soil inorganic N to available N by 68.61%, 65.09%, 56.47% and 63.00%, but increased the rate of soil hydrolysable organic N to available N by 4.18, 4.21, 3.66 and 4.08 times, respectively. Compared with the control, growing soybean, cotton, maize and sorghum significantly increased the transform rate of ammonium nitrogen fertilizer by 93.66%, 38.19%, 32.58% and 38.31% respectively, and growing soybean treatment had the highest increasing range; the nitrification rates of ammo- nium nitrogen fertilizer of growing soybean, cotton, maize and sorghum treatments were negative values, and growing soybean treatment had the highest decreasing amplitude. The ammonium nitrogen fertilizer use efficiency of growing soybean, cot- ton, maize and sorghum treatments were 52.01%, 28.31%, 24.16% and 28.40% re- spectively and growing soybean treatment had the highest value. In conclusion, growing crops suppressed the soil nitrification and accelerated the development of soil hydrolysable organic nitrogen by the utilization of soil available nitrogen and the alteration of soil environment, and hence impacted the constitution of soil available nitrogen and the transform and use of ammonium nitrogen applied in soil. Legumi- nous crops had stronger ability of suppressing nitrification, making use of ammonium compared with non-Leguminous crops.

Effects of Different Nitrogen Fertilizer Rates on Soluble Sugar,Starch and Root Tissue Structure of the Peach Trees

[Objective] The research aimed to provide theoretical basis for the cultivation and production of peach.[Method] The three-year-old seedling peach tree was used as the materials,and NH4NO3 was used as the experimental nitrogen fertilizer.Three nitrogen levels,0,3,6 g per pot respectively were set to study the effects of different nitrogen fertilizer on the contents of soluble sugar,starch and internal structure of the root of the peaches.[Result] The contents of soluble sugar of roots and leaves increased with the increase of nitrogen fertilizer level,and the level of 6 g per pot was the highest,which showed extreme differences between the level of 3 g per pot and the control.However,starch contents showed opposite results,which decreased as the level of nitrogen fertilizer increased.Compared with the 3 g per pot level of nitrogen fertilizer and the control,the internal structure of root applied with nitrogen fertilizer of 6 g per pot level had larger fibrovascularcylinder,advanced vascular bundle,small-spaced thin-walled cells,smooth and full cells with smooth cell wall.[Conclusion]Appropriate nitrogen levels can accelerate the accumulation of soluble sugar and the growth of root tissue structure.

Total Amount Control Test of Nitrogen Fertilizer and Phosphate Fertilizer on Winter Wheat

[Objective] This study was conducted to optimize the suitable application amounts of nitrogen fertilizer and phosphate fertilizer for winter wheat.[Method] A field experiment was carried out to investigate the effects of the application amounts of nitrogen fertilizer and phosphate fertilizer on the yield of winter wheat.[Result]The quadratic simulation function between the application of nitrogen fertilizer and wheat yield was y =-0.6611x^2＋20.091 x ＋234.85,with a correlation coefficient of0.970 8,and the yield of winter wheat was the highest at the application amount of nitrogen fertilizer of 228.0 kg/hm^2.The quadratic simulation function between the application of phosphate fertilizer and wheat yield was y =-0.572 6x^2＋13.168 x ＋340.4,with a correlation coefficient of 0.921 95,and the yield of winter wheat was the highest at the application amount of phosphate fertilizer of 172.5 kg/hm^2.[Conclusion] This study provides a scientific basis for the rational application of nitrogen fertilizer and phosphate fertilizer on winter wheat.

Effects of Different Irrigation Times and Nitrogen Fertilizer Application on Leaf Area Index and Grain Yield of ‘Yujiao 5'

To provide ＂more reasonable, more saving and more efficient＂ water and fertilizer application proposals, taking ‘Yujiao 5＇ as the experimental material, the effects of different irrigation times and nitrogen application treatments on the leaf area index and yield of wheat were studied using three-factor split plot method. The results showed that irrigation times, nitrogen application rate and the ratio of basa to topdressed nitrogen respectively had significant effects on the leaf area index, the yield and component factors of wheat. Under the treatment of W1（irrigation before sowing）, the leaf area index showed a positive linear correlation with nitrogen application rate; under the treatments of W2（irrigation before sowing and at jointing stage） and W3（irrigation before sowing, at jointing stage and at grain filling stages）,the leaf area index showed a positive linear correlation with nitrogen application rate at the jointing stage, booting stage and heading stage; 20 d after heading, the leaf area index showed a quadric curve relationship with nitrogen application rate at these stages, and the LAI of N3R2 was the highest. Under different irrigation times,the yield, ear number and kernels per ear showed quadric curve relationship with nitrogen application rate, 1 000-seed weight showed the trend of linear decrease with the increase of nitrogen application rate. Under the treatment combination of irrigation before sowing, at jointing stage and at grain filling stage, nitrogen application rate at 240 kg/hm^2 and the ratio of basal to topdressed nitrogen of 5：5, the grain yield（8 609.60 kg/hm^2）, ear number（688.2×104/hm^2） and kernel number per ear（37.9 grains） reached the highest value at W3N3R2, and the grain yield of W3N3R2 increased by 144.8% compared to the W1N0. In conclusion, in Eastern Henan where the rainfall is insufficient at the late growth stage of wheat, the irrigation-saving space in wheat production is relatively small, but the nitrogen-saving space is relatively large.

Leaching and Transformation of Nitrogen Fertilizers in Soil After Application of N with Irrigation: A Soil Column Method

A soil column method was used to compare the effect of drip fertigation (the application of fertilizer through drip irrigation systems, DFI) on the leaching loss and transformation of urea-N in soil with that of surface fertilization combined with flood irrigation (SFI), and to study the leaching loss and transformation of three kinds of nitrogen fertilizers (nitrate fertilizer, ammonium fertilizer, and urea fertilizer) in two contrasting soils after the fertigation. In comparison to SFI, DFI decreased leaching loss of urea-N from the soil and increased the mineral N (NH4+-N + NO3- -N) in the soil. The N leached from a clay loam soil ranged from 5.7% to 9.6% of the total N added as fertilizer, whereas for a sandy loam soil they ranged between 16.2% and 30.4%. Leaching losses of mineral N were higher when nitrate fertilizer was used compared to urea or ammonium fertilizer. Compared to the control (without urea addition), on the first day when soils were fertigated with urea, there were increases in NH4+-N in the soils. This confirmed the rapid hydrolysis of urea in soil during fertigation. NH4+-N in soils reached a peak about 5 days after fertigation, and due to nitrification it began to decrease at day 10. After applying NH4+-N fertilizer and urea and during the incubation period, the mineral nitrogen in the soil decreased. This may be related to the occurrence of NH4+-N fixation or volatilization in the soil during the fertigation process.

Effects of Different Nitrogen Fertilizer Levels on Fe,Mn,Cu and Zn Concentrations in Shoot and Grain Quality in Rice (Oryza sativa)

In a pot experiment, effects of N fertilizer application on the concentrations of Fe, Mn, Cu and Zn in shoot of rice and the quality of brown rice were studied. In the treatments with N fertilizer application, the concentrations of Fe, Mn, Cu and Zn in most parts of rice shoot increased compared with control （no N fertilizer application）. This indicated that the transportation ability of microelements from root to shoot in rice was improved with N fertilizer application. Effect of N fertilizer on IR68144 was similar to that of on IR64, but the concentrations of the microelements in plant differed, suggesting that the characteristic expression of the two rice genotypes was not controlled by the amount of N fertilizer supplied. The concentrations of those microelements in brown rice increased at first and then decreased with increasing N fertilizer application, reaching the highest at 160 kg/ha, at which the Fe, Mn, Cu and Zn concentrations in brown rice increased by 28.96%, 41.34%, 58.31% and 16.0% for IR64, and by 22.16%, 13.75%, 8.75% and 20.21% for IR68144 compared with control, respectively. Moreover, N fertilizer promoted the accumulation of protein, decreased the accumulation of amylose in grain, and enhanced gel consistency of brown rice. These results indicate that appropriate N fertilizer management could increase micronutrient contents in grain and improve nutrition quality of rice.

Efficient Management of Nitrogen Fertilizers for Flooded Rice in Relation to Nitrogen Transformations in Flooded Soils

Recent progresses in efficient management of nitrogen fertilizers for flooded rice in relation to nitrogen transformations in flooded soil were reviewed.Considerable progress has been achieved in the investigation on the mechanism of ammonia loss and the factors affecting it .However,little progress has been obtained in the investigations on nitrification-denitrification loss owing to the lack of method for estimating the fluxes of gaseous N products.Thus,so far the management practices developed or under investigation primarily for reducing ammonia loss are feasible or promising,while those for reducing nitrification-denitrification loss seem obscure,except the point deep placement. In addition,it was emphasized that the prediction of soil N supply and the recommendation of the optimal rate of N application based on it are only semi-quantitative.The priorities in research for improving the prediction are indicated.

Effect of Nitrogen Fertilizer on Herbivores and Its Stimulation to Major Insect Pests in Rice

Nitrogen is one of the most important factors in development of herbivore populations. The application of nitrogen fertilizer in plants can normally increase herbivore feeding preference, food consumption, survival, growth, reproduction, and population density, except few examples that nitrogen fertilizer reduces the herbivore performances. In most of the rice growing areas in Asia, the great increases in populations of major insect pests of rice, including planthoppers （Nilaparvata lugens and Sogatella furcifera）, leaffolder （ Cnaphalocrocis rnedinalis）, and stem borers （Scirpophaga incertulas, Chilo suppressalis, S. innotata, C. polychrysus and Sesarnia inferens） were closely related to the long-term excessive application of nitrogen fertilizers. The optimal regime of nitrogen fertilizer in irrigated paddy fields is proposed to improve the fertilizer-nitrogen use efficiency and reduce the environmental pollution.