Effects of nitrogen application rate and hill density on rice yield and nitrogen utilization in sodic saline–alkaline paddy fields

Soil salinity and alkalinity can inhibit crop growth and reduce yield,and this has become a global environmental concern.Combined changes in nitrogen (N) application and hill density can improve rice yields in sodic saline–alkaline paddy fields and protect the environment.We investigated the interactive effects of N application rate and hill density on rice yield and N accumulation,translocation and utilization in two field experiments during 2018 and 2019 in sodic saline–alkaline paddy fields.Five N application rates (0 (control),90,120,150,and 180 kg N ha^(-1) (N0–N4),respectively) and three hill densities(achieved by altering the distance between hills,in rows spaced 30 cm apart:16.5 cm (D1),13.3 cm (D2) and 10 cm (D3))were utilized in a split-plot design with three replicates.Nitrogen application rate and hill density significantly affected grain yield.The mathematical model of quadratic saturated D-optimal design showed that with an N application rate in the range of 0–180 kg N ha^(-1),the highest yield was obtained at 142.61 kg N ha^(-1) which matched with a planting density of 33.3×10^(4) ha^(-1).Higher grain yield was mainly attributed to the increase in panicles m^(–2).Nitrogen application rate and hill density significantly affected N accumulation in the aboveground parts of rice plants and showed a highly significant positive correlation with grain yield at maturity.From full heading to maturity,the average N loss rate of the aboveground parts of rice plants in N4 was 70.21% higher than that of N3.This is one of the reasons why the yield of N4 treatment is lower than that of the N3 treatment.Nitrogen accumulation rates in the aboveground parts under treatment N3 (150 kg N ha^(-1)) were 81.68 and 106.07% higher in 2018 and 2019,respectively,than those in the control.The N translocation and N translocation contribution rates increased with the increase in the N application rate and hill density,whereas N productivity of dry matter and grain first increased and then decreased with the increase in N application rate and hill density.Agronomic N-use efficiency decreased with an increase in N application rate,whereas hill density did not significantly affect it.Nitrogen productivity of dry matter and grain,and agronomic N-use efficiency,were negatively correlated with grain yield.Thus,rice yield in sodic saline–alkaline paddy fields can be improved by combined changes in the N application rate and hill density to promote aboveground N accumulation.Our study provides novel evidence regarding optimal N application rates and hill densities for sodic saline–alkaline rice paddies.

Effects of Nitrogen Dosage on the Yield and Nitrogen Use Efficiency of Machine Transplanted Rice Using Dry Soil Preparation in Rice Paddy Field

[Objective] The aim was to analyze the effects of nitrogen dosage on the yield and nitrogen use efficiency of machine transplanted rice using the technology of dry soil preparation in rice paddy field. [Method] With conventional Japonica rice cultivar Shengdao 18 as the study material, the effect of nitrogen dosage on stem and tillers dynamics, yield components and nitrogen use efficiency were investigated using the technology of dry soil preparation in rice paddy field. [Result] The highest yield was 10 957.20 kg/hm^2 as the nitrogen application was 315.00 kg/hm^2. Meanwhile, the roughness ratio, grain-straw ratio and nitrogen use efficiency remained at a higher level. Low nitrogen application could not obtain high yield. In contrast, high nitrogen application quantity led to a significant decline in nitrogen use efficiency. [Conclusion] The study could provide a scientific basis for the further promotion of the technology of dry soil preparation in rice paddy field.

Effects of straw and biochar addition on soil nitrogen,carbon,and super rice yield in cold waterlogged paddy soils of North China

The additions of straw and biochar have been suggested to increase soil fertility, carbon sequestration, and crop produc- tivity of agricultural lands. To our knowledge, there is little information on the effects of straw and biochar addition on soil nitrogen form, carbon storage, and super rice yield in cold waterlogged paddy soils. We performed field trials with four treatments including conventional fertilization system （CK）, straw amendment 6 t ha^-1 （S）, biochar amendment 2 t ha^-1 （C1）, and biochar amendment 40 t ha^-1 （C2）. The super japonica rice variety, Shennong 265, was selected as the test Crop. The results showed that the straw and biochar amendments improved total nitrogen and organic carbon content of the soil, reduced N2O emissions, and had little influence on nitrogen retention, nitrogen density, and CO2 emissions. The S and C1 increased NH4^＋-N content, and C2 increased NO3^--N content. Both S and C1 had little influence on soil organic carbon density （SOCD） and C/N ratio. However, C2 greatly increased SOCD and C/N ratio. C1 and C2 significantly improved the soil carbon sequestration （SCS） by 62.9 and 214.0% （P〈0.05）, respectively, while S had no influence on SCS. C1 and C2 maintained the stability of super rice yield, and significantly reduced CH4 emissions, global warming potential （GWP）, and greenhouse gas intensity （GHGI）, whereas S had the opposite and negative effects. In summary, the biochar amendments in cold waterlogged paddy soils of North China increased soil nitrogen and carbon content, improved soil carbon sequestration, and reduced GHG emission without affecting the yield of super rice.

Discrepancy in Response of Rice Yield and Soil Fertility to Long-Term Chemical Fertilization and Organic Amendments in Paddy Soils Cultivated from Infertile Upland in Subtropical China

From 1990,over 17 years field experiment was carried out in paddy field cultivated from infertile upland to evaluate the response of rice productivity,soil organic carbon（SOC）,and total N to long-term NPK fertilization or NPK combined with organic amendments.The field trials included NPK（N,P,K fertilizer）,NPKRS（NPK combined with rice straw）,NPK2RS（NPK combined with double amount of rice straw）,NPKPM（NPK combined with pig manure） and NPKGM（NPK combined with green manure） and the cropping system was rice-rice（Oryza sativa L.） rotation.Annual rice yield,straw biomass,and harvesting index increased steadily with cultivation time in all treatments.Average annual rice yield from 1991 to 2006 was ranged from 7 795 to 8 572 kg ha-1 among treatments.Rice yields in treatments with organic amendments were usually higher than that in treatment with NPK.Contents of SOC and total N also increased gradually in the cultivation years and reached the level of 7.82 to 9.45 and 0.85 to 1.03 g kg-1,respectively,in 2006.Soil fertilities in treatments with chemical fertilization combined with organic amendments were relatively appropriate than those in treatment with NPK.There was obvious discrepancy between cumulative characters of rice yield and soil organic fertility in newly formed paddy field.Compared with relatively high rate of crop productivity improvement,cumulative rates of SOC and total N were much lower in our study.SOC and total N contents were still less than half of those in local highly productive paddy soils after 17 years cultivation in subtropical China.Present work helps to better understand the development of infertile paddy soils and to estimate the potential of yield improvement in this region.

Effects of Micro-Topographic Reestablishment on Paddy Impoundment and Rice Yield

From a perspective of cultivation measures, it was needed to develop a new paddy impoundment model to achieve higher rice yield with higher water utilization efficiency. This study was conducted to quantify the effect of ridge- tillage terrace ecological rice farming （RT）, bed ecological rice farming （B） and conventional ecological rice farming （CK） on the paddy impoundment model and rice yield, and determine dry matter accumulation （DMA）, rice yield, yield component, and parameters of the ridge tillage and the bed. The RT could be used to achieve the dual improvement in the capacity of natural precipitation storage and in soil aeration by dry-wet alternation damp irrigation. Water storage capacity in the RT was 29% higher than that of the CK and most of the water was stored in the ditch. The grain yield of each of different rice cultivars （except the cultivar Huanghuazhan in 2011） in the RT was significantly higher than that of the CK. The total DMA in the RT was 16.5% in 2011 and 28.2% in 2012 higher than that of the CK, respectively. The variation of DMA before and after the full-heading stage among rice cultivars was inconsistent. Consequently, the RT was an effective measurement of micro- topographic reestablishment for changing paddy impoundment model, increasing water storage capacity, especially the natural precipitation storage, and increasing rice yield.

Effects of Once Fenlong Cultivation on Soil Properties and Rice Yield and Quality for 7 Consecutive Years

[Objective] The objective of this study was to explore the long-term effect of Fenlong cultivation for one time. [Method] The physical and chemical properties of soil and rice yield and quality were investigated and determined by measuring the soil at the depth of 23 cm in the paddy field with Fenlong cultivation and 16 cm of control （conventional farming） for 7 years. [Result] Compared with the control, the average yield of early rice of the Fenlong cultivation increased by 1 972.5 kg/hm2 of the first year, an increase of 23.87%, and milled rice and protein increased by 15.95% and 14.61%, while the increase rates of organic matter, available nitrogen, available phosphorus and available potassium per hectare were 74.58%, 67.01%, 104.41% and 129.62%, respectively. In the 7th year after Fenlong cultivation, the yield increased by 234 kg/hm2 from the control, an increase of 3.21%, and milled rice and protein increased by 0.5% and 0.14%, while the increase rates of organic matter, available phosphorus and available potassium per hectare were 745.8%, 62.635 and 73.37%, respectively, and the increase rates of total nitrogen, total phosphorus and total potassium were 46.03%, 50.58% and 36.65%, respectively. During the 7 years after Fenlong cultivation, the yield increased by 3.21-23.87%, and its average net income per season increased by 1 843.61 Yuan/hm2 with a gain of 18.03%. [Conclusion] At the 7th year after Fenlong cultivation, the paddy field still had the furrow remain at a depth of 22 cm, which was 46.67% thicker than the traditional one. The yield and quality of paddy rice increased for 7 consecutive vears showed that Fenlon.q cultivation was highly feasible for paddy field.

施氮量对川东南冬水田稻鱼共作系统下杂交稻产量和土壤养分的影响

【目的】利用川东南冬水田区连续多年稻鱼共作系统,研究施氮(N)量对免耕栽培杂交稻产量形成和土壤养分的影响,为制定稻鱼共作系统下免耕栽培杂交稻长期、合理的氮肥管理策略提供理论依据。【方法】于2018—2022年在川东南冬水田区开展了5年大田定位试验,供试杂交稻品种为蓉优1015和内6优103,耕作方式为免耕。设置N 0、45、90、135 kg/hm^(2)4个施氮水平,分别记作N_(0)、N_(45)、N_(90)、N_(135)。在水稻收获期,调查杂交稻产量及产量构成因素,分析0—20 cm土层土壤全量和速效氮、磷、钾含量,以及有机质含量和pH,通过回归分析,研究施氮量与水稻产量和土壤养分因子含量变化之间的关系。【结果】稻鱼共作系统下,年份、施氮量对杂交稻产量及产量构成的影响达极显著水平。5年间,杂交稻产量与施氮量均呈极显著正相关(r=0.9070^(**)~0.9720^(**)),与低氮量处理N_(45)相比,N_(90)和N_(135)处理杂交稻产量分别增加了6.37%~26.53%、9.11%~25.11%,单位面积有效穗数和每穗粒数也显著增加。而N_(90)处理杂交稻产量与N_(135)处理相当或更高。逐步回归分析结果表明,杂交稻产量构成(单位面积有效穗数、每穗粒数、结实率和千粒重)与产量的偏相关系数达显著或极显著水平(t=2.20*~9.17^(**))。通径分析结果表明,杂交稻单位面积有效穗数和每穗粒数对产量的直接贡献(分别为0.8754和0.4987)和总贡献(分别为0.6364和0.3598)较大,表明单位面积有效穗数和每穗粒数是影响产量的主要因素。在N_(0)、N_(45)处理下,土壤全氮、碱解氮含量随稻鱼共作年限的增加而下降,而在N_(90)、N_(135)处理下随稻鱼共作年限的增加而增加。土壤全氮、碱解氮含量随施氮量增加而提高,而全磷、全钾、速效磷、速效钾含量则随施氮量增加而下降。杂交稻产量与土壤养分含量呈极显著正相关,可见提高磷素、钾素供给能力是稻鱼共作系统杂交稻高产的重要基础。【结论】川东南冬水田区稻鱼共作系统下,年施氮90 kg/hm^(2)可以提高杂交水稻的单位面积有效穗数和每穗粒数,进而维持甚至提高水稻产量。连续施用中、高量氮肥还可以提升土壤有机质、全氮、全磷、全钾、碱解氮、速效磷和速效钾含量,且随稻鱼共作年限延长呈增加趋势;土壤pH值则随稻鱼共作年限延长呈下降趋势。

节水灌溉下秸秆还田形式对黑土区稻田N_(2)O排放与产量的影响

为探寻不同灌溉模式下秸秆还田形式对黑土区稻田N_(2)O排放与产量的影响,于2023年进行大田试验,设置常规灌溉(F)与控制灌溉(C)两种灌溉模式,同时设置秸秆还田(S)、秸秆炭化为生物炭还田(B)、秸秆过牛腹为有机肥还田(O)3种还田形式,以及秸秆不还田(N)作为对照组,共计8个处理。分析不同灌溉模式下秸秆还田形式对稻田N_(2)O排放通量与水稻产量的影响,测定了水稻各生育期稻田土壤铵态氮含量、硝态氮含量、微生物氮含量、pH值,并分析了N_(2)O排放总量和水稻产量与土壤环境因子之间的关系。结果表明:除返青期外,与秸秆不还田处理相比,秸秆还田与有机肥还田处理土壤铵态氮含量、硝态氮含量、微生物氮含量均表现为增加。相同秸秆还田形式下,控制灌溉模式下各处理生育期内土壤平均铵态氮含量、硝态氮含量较常规灌溉模式高36.23%~60.82%、14.16%~19.61%。同时,秸秆还田与生物炭还田能提高稻田土壤pH值。相同灌溉模式下,与秸秆不还田处理相比较,秸秆还田与有机肥还田处理N_(2)O排放总量分别增加14.44%~24.09%、8.22%~14.44%,生物炭还田处理N_(2)O排放总量降低14.31%~23.90%。生物炭还田与有机肥还田各处理水稻产量提高3.28%~13.07%,其中控制灌溉模式下生物炭还田处理产量最高。综上所述,控制灌溉下生物炭还田可以实现节水、增产、减排的目的。

硝化抑制剂双氰胺施用对水稻产量和温室气体排放的影响

为探究施用硝化抑制剂双氰胺对水稻产量和温室气体排放的影响,以常规粳稻品种南粳9108为供试材料进行盆栽试验,设置常规氮肥(CK)和常规氮肥配施硝化抑制剂双氰胺(DCD)2个处理。采用静态箱-气相色谱法连续监测稻田温室气体排放动态变化。结果表明,与CK相比,DCD显著提高了水稻产量(15.1%)和地上部生物量(28.4%),并且显著降低了稻田甲烷(CH_(4))累积排放量(22.2%)、氧化亚氮(N_(2)O)累积排放量(56.0%)、综合温室效应(GWP)(24.4%)和温室气体排放强度(GHGI)(31.7%)。可见,常规氮肥配施硝化抑制剂双氰胺可以协同实现水稻丰产和稻田温室气体减排。

稻田不同水旱复种模式对土壤团聚体及碳氮的影响

【目的】探寻更适合南方稻田可持续发展的水旱复种模式。【方法】在江西农业大学科技园开展紫云英−早稻−晚稻(CK)、紫云英−早稻−晚玉米||晚大豆(CRI)、油菜−早稻−晚玉米||晚大豆(RRI)、油菜−早稻−晚稻(RRR)水旱复种模式的田间对比试验。【结果】土壤有机碳、全氮含量均为CK>RRR>CRI>RRI。种植紫云英模式的R0.250(粒径≥0.250 mm的团聚体含量)比种植油菜模式的高,土壤结构的稳定性更强。CRI的早稻产量高于其他处理。【结论】在南方地区推行紫云英−早稻−晚玉米||晚大豆种植模式(CRI),有利于农业的可持续发展。

绿肥油菜还田提高水稻产量与土壤磷钾肥力

为评价太湖地区油菜花后作绿肥对水稻产量及稻田水土养分的影响,在太湖地区连续进行2年田间定位试验,明确在2种不同油菜-水稻种植模式[绿肥油菜-水稻、饲用油菜-水稻(CK)]引起的水稻籽粒产量、产量构成因子、土壤氮磷钾含量以及稻田田面水氮磷浓度变化。结果表明:与对照处理相比,油菜终花期后压青还田下2年水稻产量提高了6.1%~15.2%,试验第1年水稻产量显著增加主要是由于有效穗数显著增加了20.0%,成穗率显著提高了14.7%,穗实粒数显著提高13.1%(P<0.05),结实率、千粒质量2种处理差异无统计学意义。连续2年绿肥油菜还田下耕层土壤全氮含量差异无统计学意义,但速效磷和速效钾含量分别显著提高了31.6%和27.8%,同时移栽至分蘖期稻田田面水总氮和总磷浓度分别显著提高36.3%和53.7%(P<0.05)。由此,太湖地区油菜作绿肥还田可维持水稻产量并补充土壤磷钾库,但应结合配套油菜绿肥还田技术以降低稻田盈余养分潜在流失风险,为太湖保护区提供化学肥料有机替代和绿色防控等有效环保型施肥技术。

Integrated rice management simultaneously improves rice yield and nitrogen use efficiency in various paddy fields

The hilly area of Southwest China is a typical rice production area which is limited by seasonal droughts and low temperature in the early rice growth period.A field experiment was conducted on three typical paddy fields(low-lying paddy field,medium-elevation paddy field,and upland paddy field)in this region.Nitrogen(N)treatment(180 kg N ha-1 year-1)was compared to a control treatment(0 kg N ha-1 year-1)to evaluate the effects of integrated rice management(IRM)on rice growth,grain yield,and N utilization.Integrated rice management integrated raised beds containing plastic mulch,furrow irrigation,and triangular transplanting.In comparison to traditional rice management(TRM),IRM promoted rice tiller development,with 7–13 more tillers per cluster at the maximum tillering stage and 1–6 more tillers per cluster at the end of tillering stage.Integrated rice management significantly increased the rice aboveground biomass by 34.4%–109.0%in different growth periods and the aboveground N uptake by 25.3%–159.0%.Number of productive tillers significantly increased by 33.0%,resulting in a 33.0%increase in grain yield and 8.0%improvement of N use efficiency(NUE).Grain yields were significantly increased in all three paddy fields assessed,with IRM being the most important factor for grain yield and productive tiller development.Effects of paddy field type and N level on N uptake by aboveground plants were reflected in the rice reproductive growth period,with the effects of IRM more striking due to the dry climate conditions.In conclusion,IRM simultaneously improved rice yield and NUE,presenting a valuable rice management technique in the paddy fields assessed.

碱性材料和有机物料对稻田土壤酸化改良及水稻产量的影响

为了在酸化稻田的改良过程中,同步实现土壤降酸和土壤肥力提升的双目标,通过田间试验设置了常规施肥(CK)、CK+石灰(T1)、CK+猪粪(T2)、CK+微生物菌剂(T3)和CK+石灰+猪粪(T4)这5个处理,分析了土壤酸化指标、肥力指标和水稻产量及产量构成的变化特征。结果表明:与CK处理相比,T1和T4处理的土壤pH分别提高了0.24和0.33个pH单位,土壤交换性酸分别降低了16.8%和25.4%,土壤交换性铝含量分别降低了50.8%和75.4%;而T2处理的土壤交换性酸和交换性铝含量则比CK处理降低了19.3%和59.0%,但其土壤pH值与CK无显著差异。T4处理的土壤有机质、碱解氮、有效磷、速效钾和阳离子交换量分别比CK处理增加了9.2%、78.0%、21.8%、23.2%和52.9%,T1、T2和T3处理的土壤有机质、碱解氮、有效磷和阳离子交换量则无显著变化,但是,T1、T2和T3处理的土壤速效钾则显著高于CK处理。在所有处理中,T2和T4处理的水稻产量较高,分别比CK处理增加了6.8%和8.4%,结合产量构成因子发现,猪粪及其与石灰联用主要通过改善结实率提升水稻产量。因此,在酸化稻田改良中,石灰和猪粪联用是协同实现土壤酸化改良和肥力及产能提升的合理措施。

豫南稻虾共作模式下施氮量对再生稻产量和效益的影响

为研究豫南稻区稻虾共作模式下再生稻田的适宜施氮量,以豫南再生稻主栽品种‘天两优616’为供试品,于2022年在商城县上石桥镇开展试验,相同的田间管理条件下设6个不同的氮肥水平处理N0(0 kg/hm^(2))、N1(249.27 kg/hm^(2))、N2(302.69 kg/hm^(2))、N3(356.10 kg/hm^(2))、N4(409.52 kg/hm^(2))、N5(462.93 kg/hm^(2)),研究不同施氮量对虾田再生稻两季产量和经济效益的影响。结果表明:随着氮肥施用量的增加,虾田再生稻两季产量呈先增后减的趋势,其中N4处理产量最高;氮肥农学利用率和偏生产力随着氮肥水平的增加而下降;随着施氮量的增加,再生稻周年经济效益为负值,综合经济效益曲线表明,当氮肥施用量为386.68 kg/hm^(2)时能够获得最佳收益。研究表明,适当增施氮肥能增加再生稻产量和经济效益,豫南稻区再生稻田稻虾共作模式最佳施氮量以386.68 kg/hm^(2)为宜。本研究可为豫南稻区稻虾共作模式下再生稻田合理施氮提供理论基础,促进虾田再生稻的推广应用。

红壤稻田长期施钾肥及有机肥对水稻叶面积指数及产量构成的影响

在实施了29年定位施肥试验的红壤稻田,进行了水稻叶面积的测量分析和水稻产量构成分析。结果表明:抽穗期叶面积指数增施钾肥提高13.0%,增施有机肥提高47.0%。钾效应系数为13.0%,有机肥效应系数为14.3%。产量构成方面,增施钾肥有效穗数提高5.1%,每穗总粒数提高15.3%,结实率提高0.8%,千粒重提高5.5%;增施有机肥有效穗数降低1.3%,每穗总粒数增加11.8%,结实率降低2.0%,千粒重降低13.0%。

渍水时间对油菜生长及产量的影响

长江流域油菜生产期间雨水偏多,加上主要采用水稻油菜轮作模式,地下水位高、土壤黏重,常发生渍害。为了研究油菜各生育期渍水对其生长及产量形成的影响,设计盆栽试验,在油菜4个生育期分别进行3个不同渍水时间处理后,然后恢复正常水分管理。其中,苗期、蕾薹期分别进行10、20和30d渍水处理,花期、角果期分别进行10、15和20d渍水处理,各处理4次重复,比较2个耐渍性不同的油菜品系在各生育期的生长状况及产量。结果表明:(1)渍水影响油菜各生育期根系发育、地上部生长及最终产量的形成,并存在品种间差异;(2)苗期渍水导致叶片叶绿素(Chl)含量下降、丙二醛(MDA)及脯氨酸(Pro)含量增加,其变化过程在指标间存在差异;(3)以产量为指标,渍水的敏感性依次为蕾薹期、花期>苗期、角果发育成熟期;(4)研究不同渍水处理对产量的影响可为持续降雨对大面积油菜生产影响的估算提供依据。

四川盆地水稻产量对基础地力与施肥的响应

【目的】四川盆地是中国主要的单季稻种植区之一。研究四川盆地稻田土壤基础地力、养分供应能力和施肥效果,评价土壤基础地力和施肥对水稻产量的影响,为四川盆地稻田地力的保育培肥和区域合理施肥提供依据。【方法】依托2005年以来在四川盆地布置的474个水稻田长期定位试验点,选取对照(不施肥CK)、磷钾(PK)、氮钾(NK)、氮磷(NP)和氮磷钾(NPK)5个处理,测定水稻产量和养分吸收量,分析四川盆地稻田土壤基础地力现状、土壤养分供应能力和施肥效果及其之间的关系,基于水稻产量评价不同基础地力稻田的施肥效果及产量稳定性和可持续性。同时通过调研四川盆地水稻研究结果,分析30多年来稻田基础地力的变化趋势。【结果】文献调研表明,四川盆地田基础地力稳定提升,2000年以来稻田基础地力产量在5.6—6.4 t·hm-2,比二十世纪八九十年代提高了1.5 t·hm-2,地力贡献率也上升6.7%。田间试验表明,基础地力和肥料对产量的贡献率分别为67.4%—75.9%和24.1%—32.6%。四川盆地稻田土壤氮、磷、钾养分供应量分别为103—120、23.2—27.5和139—185 kg·hm-2,土壤养分对产量的平均贡献率达到78.2%、88.8%、90.8%,而施肥对产量的贡献率低于30%,且氮肥的增产效果高于磷肥和钾肥。四川盆地不同生态区土壤基础地力和养分供应能力均表现为成都平原>盆地中部浅丘区>盆地周边丘陵区>盆地东部丘陵区;土壤基础地力越高越容易实现水稻高产,土壤基础地力与土壤贡献率呈显著正相关,而与肥料贡献率呈显著负相关;土壤基础地力越高,产量可持续性和稳定性越高。【结论】提高稻田土壤基础地力可促进水稻高产稳产,降低高产对肥料的依赖性,有利于水稻的可持续生产。

太湖地区稻田减量施肥的环境效益和经济效益分析

通过设置不同幅度的氮肥减量施用,研究其在整个稻季中的环境效益、肥料效益和产量效益差异,为地区氮肥的减施增效提供依据。结果表明:稻田施肥后7 d之内,田面水中氮素含量维持较高水平,须谨慎控制田面水外排。在太湖地区现有肥力水平的基础上,适当减少氮肥用量是可行的。减少20%的常规施氮量可以有效降低田面水中氮素含量,进而降低向自然环境中排放的总氮量;并通过作用于水稻产量构成因素和提高氮肥农学效率,适当提高产量,最终达到协调产量效益、肥料效益和环境效益的目的。

轮耕对土壤物理性状及水稻产量影响的初步研究

针对南方稻田连续免耕存在的主要问题，进行了土壤轮耕效应的初步研究。试验选择双季稻区连续7年免耕稻田，设置免耕、旋耕和翻耕3种耕作处理（即免耕-免耕，免耕-旋耕和免耕-翻耕），早稻和晚稻采取同-耕作措施。研究结果表明：连续免耕后进行土壤耕作（翻耕、旋耕）可以降低耕作层土壤容重，增加土壤水贮量，尤为翻耕显著，早、晚稻均表现为这-趋势；晚稻收获时，表层0～5cm的毛管孔隙度表现为免耕-翻耕、免耕-旋耕在5％水平上显著高于免耕-免耕，而下层差异不显著；早、晚稻晒田时，表层0～5cm原状土饱和导水率均表现为免耕～翻耕在5％水平上显著高于免耕-免耕和免耕-旋耕，而5～10cm无显著性差异；早、晚稻的实际产量均表现为免耕-旋耕〉免耕-翻耕〉免耕-免耕，起主要作用的构成因素是有效穗数。

高、中、低产田水稻适宜施氮量和氮肥利用率的研究

为探明不同施氮水平对湖北省高、 中、 低产田水稻产量和氮肥利用率的影响。选用水稻品种两优培九为供试品种，采用大田小区试验，探索不同地力水平（高、 中、 低）下稻田的最佳施氮量，考察不同施氮水平对不同地力水平水稻产量及产量构成因素、 氮肥贡献率、 土壤氮素依存率和氮肥利用率的影响规律。结果表明， 在2011年大田试验中，高产田和中产田都在施氮量为N 180 kg/hm2 的处理中获得最高产量，分别比CK增产10为探明不同施氮水平对湖北省高、 中、 低产田水稻产量和氮肥利用率的影响。选用水稻品种两优培九为供试品种，采用大田小区试验，探索不同地力水平（高、 中、 低）下稻田的最佳施氮量，考察不同施氮水平对不同地力水平水稻产量及产量构成因素、 氮肥贡献率、 土壤氮素依存率和氮肥利用率的影响规律。结果表明， 在2011年大田试验中，高产田和中产田都在施氮量为N 180 kg/hm^2 的处理中获得最高产量，分别比CK增产10.70%、 27.23%；而低产田则是在施氮为N 240 kg/hm^2处理中产量达到最大，比CK增产44.70%。在2012年大田试验中，高产田、 低产田均在施氮为N 180 kg/hm^2 时达到最高产量，分别比CK增产12.43%、 74.19%；而中产田在施氮处理为N 240 kg/hm^2 时达到最大，比CK增产28.80%。在一定范围内，施氮量越高，氮肥农学利用率和氮肥生理利用率越高，偏生产力越低。综合产量、 产量构成因子以及氮肥利用率得出高产田与中产田适宜施氮量为N 120~180 kg/hm^2，低产田适宜施氮量为N 180~240 kg/hm^2。适宜施氮量上低产田〉中产田〉高产田。