Finger millet (Eleucine corocana L. Gaertn.) as a cover crop on weed control, growth and yield of soybean under different tillage systems

Adoption of conservation tillage systems has become more popular in recent years due to erosion control and economics. Weed control is often identified as the limiting factor in the adoption of such systems. Although herbicides are efficient and convenient, the need to reduce herbicide use has been emphasized. Cover crops have become a viable option in this context, but the contribution of cover crops to weed control has not been clearly defined. A 2-year field experiment compared minimum tillage (MT), no-tillage (NT) and conventional tillage (CT) for soybean [Glycine max (L.) Merr.] following paddy rice (Oryza sativa L.) with finger millet (Eleucine corocana L. Gaertn.) as a cover crop. Weed emergence, cover crop biomass, main crop growth and yield were observed. Finger millet effectively controlled weeds but total weed biomass was greater with NT than other tillage methods and seeding method had no effect at early stage of growth. Neither crop growth nor leaf chlorophyll content was affected by finger millet under given tillage treatments. Weed biomass was almost half under MT than NT. Finger millet was able to effectively manage weed biomass under MT to a level achieved under CT without a cover crop at the early stage of growth. Number of seeds per pod and 100 seed weight were not affected by tillage treatments but number of pods per square meter was significantly higher with row seeding than broadcast seeding of finger millet cover crop in 2002. The absence of finger millet under MT in 2003, significantly reduced soybean grain yield. Finger millet can be managed with a single mechanical suppression as a cover crop under MT with no yield reduction.     

植物粟对模拟封存CO2泄漏的生理响应

碳捕集与封存（Carbon Capture and Storage,CCS）技术是近年来迅速发展的温室气体减排措施,是以煤为主的中国重要的战略性减排技术之一,减排量巨大。但是,CCS发展备受争议,其泄漏有可能会对周围生态系统尤其是结构单一的农田生态系统造成严重影响。本研究以北方地区主要粮食作物粟为试验对象,自主设计模拟地质封存CO₂泄漏盆栽试验,通过对植物生育期SPAD（叶绿素相对含量）、株高、根系以及产量、穗部特征等指标的观测,分析粟对CCS泄漏的响应。结果表明：（1）受CCS泄漏的影响,植物粟SPAD值显著降低,植株叶片叶绿素含量极显著下降（P＜0.01）。（2）CCS泄漏发生30d后粟的株高显著下降,根分支显著增加,植株受泄漏影响明显。（3）CCS泄漏显著降低了植株地上部干重和鲜重,但是泄漏对地下部鲜重无显著影响,地下部干重较地上部降幅偏小。（4）CCS泄漏影响下,植株粟产量下降34.92%。此外,CCS泄漏下植株穗长、穗粗、总粒重等农艺性状下降显著。     

Use of shoot reduction treatments as a means of simulating hail injury to proso millet

Abstract

Proso millet, Panicum miliaceum (L.), is a warm‐season annual grass well adapted for grain production in the western Great Plains of the United States, where risk of hail injury is greater than any other region of the United States. Because adjustment procedures and loss equations are not available, proso millet producers in this region have had limited access to crop hail insurance as a risk management tool. Our research was conducted to assess impact of shoot reduction treatments imposed at different crop growth stages on grain yield loss of proso millet grown under several environments. Our goal was to provide information for development of crop insurance adjustment procedures. We also wanted to determine the impact of shoot reduction on various grain yield components. Treatments consisted of a control and three levels of shoot reduction (33,66, and 100% of full stand) applied at four growth stages (emergence, 4‐leaf, boot, and heading stages). The experiments were conducted at two locations (Akron, CO and Carrington, ND) during 1996 and 1997 to assess treatment impact on relative grain yield (RGY), expressed as percent of control. A significant shoot reduction χ growth stage interaction was observed for RGY, indicating yield loss from increasing shoot reduction varied with growth stage. A linear reduction in RGY to increasing levels of shoot reduction was observed for the 4‐leaf, boot and heading growth stages, while RGY displayed a segmented linear response to increasing shoot reduction at emergence. Variation in grain yield, induced by shoot reduction treatments, was more consistently correlated with variation in seed number than seed weight.     

Nitrogen,Phosphorus and Potassium Interactions in Upland Rice

Upland rice is an important crop in South America, including Brazil. Nutrient interactions are important in determining crop yields. A greenhouse experiment was conducted to evaluate interaction among nitrogen (N), phosphorus (P), and potassium (K) in upland rice production. The treatments applied to upland rice grown on an Oxisol were three levels of N (N₀, N₁₅₀ and N₃₀₀ mg kg^?1), three levels of P (P₀, P₁₀₀ and P₂₀₀ mg kg^?1) and three levels of K (K₀, K₁₀₀ and K₂₀₀ mg kg^?1). These treatments were tested in a 3 × 3 × 3 factorial arrangement. Grain yield, shoot dry weight, plant height, root dry weight, maximum root length, panicle number, 1000-grain weight, and grain harvest index were significantly influenced by N, P, and K treatments. The treatment that did not receive P fertilization did not produce panicle or grain. Hence, P was most yield-limiting nutrient compared to two other nutrients. At the N₀P₀K₀ treatment, rice did not produce grains, indicating severe deficiency of these nutrients in Brazilian Oxisols. Maximum grain yield was obtained with the N₃₀₀P₂₀₀K₂₀₀ treatment. Grain yield had significant positive association with plant height, shoot dry weight, root dry weight, maximum root length, 1000-grain weight, panicle number, and grain harvest index. Among these growth and yield components, shoot dry weight had the highest positive association with grain yield and root length minimum positive association with grain yield. Hence, adopting adequate soil and crop management practices can improve growth and yield components and increase grain yield of upland rice.     

谷子播期对谷子/花生间作系统生产力的影响

间作作物的播期会影响其共生期,进而影响作物生产力和种间相互作用。为探究谷子(Setaria italic L. Beauv)播期对谷子/花生(Arachis hypogaea L.)间作系统生产力的影响,以谷子金选6号和花生大花生606为试验材料,固定花生播期为5月15日,谷子从5月15日至6月9日每5天播种1期,共设置6个播期处理(S1~S6)。通过对单间作系统中作物产量、产量构成因素等指标的测定,分析不同谷子播期条件下谷子/花生间作的作物产量、系统生产力、种间竞争力的变化。结果表明,随着谷子播期的推迟,间作系统中谷子和花生的产量均表现为先升高后降低的趋势,5月25日播种时(S3)谷子产量(4.07 t·hm^-2)和土地当量比(LER=1.24)最大,5月30日播种时(S4)花生产量(2.51 t·hm^-2)、间作总产值(4.64万元·hm^-2)和间作系统生产力(SP=2.93 t·hm^-2)最大;谷子/花生间作系统的实际产量损失大于0,具有产量优势。谷子的侵占力大于0、竞争比率大于1,花生的侵占力小于0、竞争比率小于1,间作系统中的谷子是竞争优势作物,对资源的竞争能力高于花生且受谷子播期影响较大。相关性分析及通径分析发现,在间作系统中,谷子产量与穗长呈显著正相关,与穗粗、穗重、穗粒重呈正相关,且穗长对谷子产量的贡献作用最大。本研究结果对谷子/花生间作实践具有指导意义。     

Influence of variety and nitrogen fertilizer on productivity and trait association of malting barley

Poor soil fertility is a major constraint to crop productivity in the highlands of Ethiopia. This study was conducted to evaluate the effects of nitrogen (N) fertilization, variety and growing season on grain yield and yield related traits, and determine relationships among agronomic traits of malting barley. The treatments studied were five N levels (0, 23, 46, 69 and 92?kg ha^?1) and two malting barley varieties (Miscal-21 and Holker) over three growing seasons (2012, 2013 and 2014) at Bekoji, south eastern Ethiopia. The results revealed that as N rates increased, grain yield, number of tillers and spikes per square meter, biomass yield at harvest, days to physiological maturity, spike length and number of kernels per spike increased, but harvest index decreased. Grain yield, harvest index, number of tillers and spikes per square meter, spike length and biomass yield at harvest were greater in Miscal-21, whilst days to maturity and number of kernels per spike were greater in Holker. Grain yield, harvest index, number of tillers and spikes per square meter, spike length, biomass yield at harvest and days to maturity were significantly affected by seasonal conditions, but spike length and kernels per spike were not affected. Grain yield was positively influenced by the number of tillers per square meter, biomass yield at harvest, spikes per square meter, spike length, kernels per spike and harvest index. However, the number of tillers per square meter followed by biomass yield and spikes per square meter largely determined grain yield. The results of the current study suggest that genetic improvement of those yield related traits is the likely basis of increasing grain yield in barley.     

Nitrogen deficiency induced a decrease in grain yield related to photosynthetic characteristics,carbon–nitrogen balance and nitrogen use efficiency in proso millet (Panicum miliaceum L.)

ABSTRACT

Field experiments involving proso millet (Panicum miliaceum L.) cultivar under four nitrogen (N) levels (N0, N60, N105 and N150) were conducted in 2015 and 2016 to explore the decrease in grain yield under N deficiency related to the changes in leaf photosynthetic characteristics, carbon (C)–N balance and N use efficiency. Results showed that N deficiency decreased the net photosynthesis rate, stomatal conductance, transpiration rate and chlorophyll content and increased the intercellular CO₂ concentration of proso millet flag leaves from flowering to maturity. N deficiency negatively regulated the C–N balance and increased the C/N ratio by reducing the total N, soluble protein and soluble sugar contents, resulting in high starch content. N uptake and utilisation were significantly reduced because of less available N. Significantly positive correlations were observed between the grain yield and photosynthetic characteristics or N use efficiency, whereas a negative correlation was found between the grain yield and the C/N ratio. The yields generated by N0, N60 and N105 were lower than that of N150 in both years. The N fertiliser regression formulae developed in the study would provide useful information about the N fertiliser rate of proso millet.     

播期对不同品种类型机插稻生长特性的影响

为了探讨河南省稻-麦两熟区播期对不同品种类型机插稻生长特性的影响,在豫南稻区罗山,以生产上主推的常规中熟中粳、常规和杂交迟熟中粳、常规早熟晚粳和迟熟中籼5个类型品种为材料,通过分期播种试验,对不同品种类型毯苗机插水稻的产量及其构成因素、茎蘖数、干物质量及群体生长率等方面进行了系统的比较研究。结果表明：1）在试验设置的播期范围内,不同品种机插稻平均产量在播期间和品种类型间差异达极显著（P<0.01）,即随着播期的推迟呈极显著下降（P<0.01）,第Ⅰ播期（5月11日,10.60 t/hm2）较第Ⅱ（5月16日）－Ⅵ（6月5日）播期分别增产2.15%～28.81%;杂交迟熟中粳产量（10.44 t/hm2）极显著高于其他4种品种类型（P<0.01）,较其他类型品种分别增产9.20%～17.53%。同一品种类型,除了中熟中粳的产量在第Ⅱ播期（5月16日）最高,随后呈显著递减趋势外,其他4种类型品种机插稻的产量均是随着播期的推迟呈极显著下降趋势（P<0.01）,但品种类型间下降幅度不同。2）在产量构成因素中,除结实率在年份间差异不显著、在播期间和品种类型间差异极显著外,其他产量构成因素在年份间、播期间和品种类型间差异均达极显著（P<0.01）。同一类型品种,除中熟中粳的结实率随播期推迟呈先略升后明显下降趋势外,其他类型品种的穗数、每穗颖花数、总颖花量、结实率和千粒质量等产量构成因素均是随播期的推迟呈显著（P<0.05）或极显著（P<0.01）下降趋势;在播期影响下,每穗颖花数和结实率的变化较大,穗数和千粒质量的变化较小;且对产量影响大小为每穗颖花数＞结实率＞穗数＞千粒质量;相关分析表明,产量与每穗粒数、总颖花量和结实率呈显著或极显著正相关,与穗数和千粒质量呈负相关;总颖花量与每穗粒数呈极显著正相关,与穗数呈负相关。进一步通径分析表明,对产量的贡献率最大的是群体颖花量,最小的是千粒质量,对群体颖花量的贡献率较大的是每穗颖花数,较小的是穗数。3）随着播期的推迟,不同品种类型水稻的茎蘖数在拔节期呈明显的递增趋势,在抽穗期和成熟期呈明显的下降趋势;单茎和群体干物质量、群体生长率在主要生育时期均呈逐渐下降趋势;成穗率和收获指数均呈逐渐下降趋势;但品种类型间和播期间下降幅度不同。综合机插稻高产及生育安全性考虑,豫南稻区首选杂交迟熟中粳"穗大粒多"型品种,适宜播期可推迟到5月25日。该研究结果为河南省豫南稻区机插水稻高产高效生产及配套品种的科学选用提供参考。     

Comparison of Conventional and Polymer Coated Urea as Nitrogen Sources for Lowland Rice Production

Nitrogen (N) is one of the most yield limiting nutrients in lowland rice production. Improving N use efficiency is essential to reduce cost of crop production and environmental pollution. A greenhouse experiment was conducted with the objective to compare conventional and polymer coated urea for lowland rice production. Grain yield, straw yield, panicle density, maximum root length, and root dry weight were significantly increased in a quadratic fashion with the increase of N rate from 0 to 400 mg kg^?1 soil. Nitrogen source X N rate interactions for most of these traits were not significant, indicating that lowland rice responded similarly to change in N rates of two N sources. Based on regression equations, maximum grain yield was obtained with the application of 258 mg N kg^?1 soil and maximum straw yield was obtained with the addition of 309 mg N kg^?1 soil. Nitrogen use efficiency (grain yield per unit of N applied) was maximum for polymer coated urea compared to conventional urea. Root length and root dry weight improved at an adequate N rate, indicating importance of N fertilization in the absorption of water and nutrients and consequently yield. Polymer coated urea had higher soil exchangeable calcium (Ca) and magnesium (Mg), Ca saturation, Mg saturation, base saturation, and effective cation exchange capacity compared to conventional urea. There was a highly significant decrease in soil exchangeable potassium (K) with increasing N rates at harvest of rice plants.     

氮肥对粳性和糯性糜子干物质积累和产量性状及氮肥利用效率的影响

为探讨不同粳糯性糜子干物质积累、产量及氮素利用效率对不同供氮水平的响应,本研究通过两年田间试验,以粳性糜子品种陇糜13号和糯性糜子品种陇糜14号为试验材料,设置45(N1)、90(N2)和135 kg·hm^-2(N3)3个供氮水平,以不施氮为对照(CK),研究不同供氮水平下不同粳糯性糜子在开花期和成熟期的干物质积累与转运、农艺性状及产量的变化,分析氮素积累量、氮肥农学利用效率、氮肥偏生产力、氮素利用率及氮肥表观利用效率对施氮的响应。结果表明,随着施氮量的增加,不同粳糯性糜子的地上部各器官干重呈单峰曲线变化,在N₂下,开花期和成熟期糜子的茎秆干重、叶片干重、茎鞘干重和穗干重均显著高于CK(P<0.05);随着施氮量的增加,不同粳糯性糜子的氮肥偏生产力呈降低趋势,而氮素利用效率呈先降低后升高的趋势;N₂可以显著提高不同粳糯性糜子的株高、茎粗、穗长、单穗粒重、千粒重及产量,也可提升氮肥农学利用效率和氮肥表观利用率。两年数据表明,N2(90 kg·hm^-2)下陇糜13号的农艺性状、产量及氮素利用效率均优于陇糜14号。综上,本研究条件下,甘肃省会宁地区糜子的推荐氮肥施用量为90 kg·hm^-2,这对西北地区种植不同粳糯性糜子具有生产指导意义。     

氮素和水分处理对稻米植酸含量和蛋白组分的影响

以直立密穗型粳稻品种秀水110和弯曲散穗型粳稻品种春江15为材料,对不同氮素水平处理和水分管理方式下稻米植酸含量和蛋白组分的影响及其互作效应进行了研究。结果表明,旱作栽培处理会导致水稻籽粒中植酸含量上升,而施氮处理对籽粒植酸含量的影响效应与水稻的水分管理方式有关,在常规水作条件下,高氮处理（N3）的籽粒植酸含量有所提高,但在旱作栽培方式下,中氮（N2）和低氮处理（N1,不施N）的籽粒植酸含量却略高于高氮处理（N3）,氮素水平与水分管理方式间的互作效应明显; 水稻籽粒植酸含量与粗蛋白总量、4种蛋白组分（清蛋白、球蛋白、醇溶蛋白和谷蛋白）及有关产量性状指标（有效穗数、每穗粒数、千粒重和结实率）在不同水肥处理间的相关性不显著,但氮肥用量过高不仅会导致水稻的产量水平下降,而且也不利于稻米营养品质的改良; 水肥处理对水稻籽粒植酸含量、蛋白总量和4种蛋白组分穗内粒位分布也存在一定影响,着生在稻穗下部的弱势粒,其稻米植酸含量高于稻穗上部或中部的强势粒,因此改善弱势粒灌浆的水肥管理措施将有利于稻米植酸含量的降低。     

YIELD AND YIELD COMPONENTS OF UPLAND RICE AS INFLUENCED BY NITROGEN SOURCES

Ammonium sulfate and urea are main sources of nitrogen (N) for annual crop production in developing countries. Two greenhouse experiments were conducted using ammonium sulfate and urea as N sources for upland rice grown on a Brazilian Oxisol. The N rates used were 0, 50, 100, 150, 3000, and 400 kg N kg^?1 of soil. Yield and yield components were significantly increased in a quadratic fashion with increasing N rate. Ammonium sulfate X urea interaction was significant for grain yield, shoot dry matter yield, panicle number, plant height and root dry weight, indicating a different response magnitude of these plant parameters to two sources of N. Based on regression equation, maximum grain yield was achieved with the application of 380 mg N kg^?1 by ammonium sulfate and 271 mg N kg^?1 by urea. Grain yield and yield components were reduced at higher rates of urea (>300 mg kg N) but these plant parameters’ responses to ammonium sulfate at higher rates was constant. In the intermediate N rate range (125 to 275 mg kg^?1), urea was slightly better compared to ammonium sulfate for grain yield. Grain yield was significantly related with plant height, shoot dry weight, panicle number, grain harvest index and root dry weight. Hence, improving these plant characteristics by using appropriate soil and plant management practices can improve upland rice yield.     

自生固氮菌的固氮能力及其对春小麦生长发育的影响

为挑选具有高固氮能力的自生固氮菌菌株, 用乙炔还原法对甘肃省春小麦和玉米等非豆科作物根际土壤中分离所得的13株菌进行固氮酶活性测定, 并通过盆栽试验对其进行春小麦肥效试验.结果表明:供试13株自生固氮菌对春小麦籽粒、生物产量及其构成因素均有一定促进作用, N6、N10、N13、N14、N27和N42 6株菌对春小麦产量的促进作用相对较高, 具有一定的应用前景, 有望成为微生物肥料研制的菌种.其中N13对春小麦的增产效果最为明显, 与施同量肥料(1/3N)的对照相比, 籽粒增产66.04%, 生物产量增产54.19%, 穗重增加47.65%, 穗粒数增多37.91%, 千粒重增加20.42%, 株高增加5.16%, 穗长增加21.89%, 且具有较强的固氮能力, 每盆固氮量为212.55 mg, 固氮酶活性也显著高于其他菌株, 达到139.79 nmol(C2H4)·h-1·mL-1.     

多效唑和乙烯利对谷子穗颈、穗部性状及灌浆的影响

为探究既能抑制谷子植株的贪青徒长,又不影响谷子产量的最佳多效唑和乙烯利处理,以农大8号为试验材料,采用随机区组设计,在谷子不同生育时期分别叶面喷施多效唑和乙烯利,研究2种植物生长调节剂单施[多效唑分别于拔节期前(A1)、拔节期(A2)、孕期期(A3)喷施;乙烯利分别于孕穗期(B1)、抽穗期(B2)、灌浆期(B3)喷施]和互作(A1B1、A1B2、A1B3、A2B1VA2B2、A2B3VA3B1、A3B2、A3B3)对谷子穗颈、穗部性状及灌浆的影响。结果表明,多效唑、乙烯利单施处理下,谷子穗颈粗、穗颈干物质显著提高,但其他穗颈参数无显著差异;谷子穗粗显著增加,在A1处理下达到最大值,较CK增加5.39%,穗重、穗粒重均在B2处理下最高,较CK分别增加7.25%、6.94%,穗长、穗码数无显著差异;籽粒灌浆速率有所提高,但秕谷率无显著变化。多效唑、乙烯利互作处理下,谷子穗颈粗、穗颈抗折力及干物质重显著增加,穗颈弯曲力矩、穗颈重心高度及含水量明显下降;谷子的穗长、穗码数显著减少,穗粗显著增加,在A1B3处理下达到最大,与CK相比,其穗长、穗码数分别减少20.11%、9.75%,穗粗增加10.15%,穗重、穗粒重均在A2B2处理下达到最大值,较CK分别增加11.45%、9.50%;随着籽粒灌浆速率的提高,秕谷率显著降低,在A2B2处理下达到最小值,较CK降低50.00%。表明与单施相比,两种调节剂互作效应更显著。在谷子拔节期前或拔节期喷施300 mg·L^-1多效唑后,在抽穗期或灌浆期追施400 mg·L^-1乙烯利最为适宜,而在孕穗期追施乙烯利会降低穗粒重,导致产量下降。本研究结果为谷子的化学调控和高产栽培提供了理论依据。     

Phosphorus Nutrition of Lowland Rice in Tropical Lowland Soil

Rice is a main food crop for about half of the world's population, and phosphorus (P) is the main limiting nutrient in rice production in tropical lowlands. A greenhouse experiment was conducted to evaluate P requirements of lowland rice grown on a lowland soil (Inceptisol). Dry matter, grain yield, and yield-attributing characteristics were significantly (P < 0.01) influenced by P fertilization. Based on quadratic response, maximum shoot dry weight and grain yield were obtained with the application of 190 mg P kg^?1 of soil. Maximum panicle, tiller number, and plant height were obtained with the application of 177 192, and 175 mg P kg^?1 of soil, respectively. Mehlich 1–extractable P for maximum grain yield was 15.6 mg kg^?1 of soil. Variability in grain yield with plant growth and yield parameters was in the order of tiller > shoot dry weight > panicle number > spikelet sterility > plant height > grain harvest index > panicle length > weight of 1000 grains. Phosphorus uptake in shoot and concentration and uptake in grain significantly (P < 0.01) increased grain yield. However, variability in grain yield was greater with concentration and uptake of P in the grain. Similarly, P harvest index was also significantly associated with grain yield. Agronomic P-use efficiency, apparent P-recovery efficiency, and P-utilization efficiency decreased quadratically with increasing P rates, whereas physiological P-use efficiency increased quadratically and agrophysiological P-use efficiency decreased linearly with increasing P rates. Agrophysiological and utilization P-use efficiencies had significant positive correlation with grain yield.     

施氮量与栽插密度对超级早稻中早22产量的影响

以超级早稻中早22为材料,采用裂区设计,研究了不同施氮量与栽插密度组合对其产量的影响.结果表明,施氮量和栽插密度及其互作对产量的影响均达显著水平.在中、低施氮水平下,不同密度间产量差异很小,而在高氮水平下,适当降低密度有利高产.在0～195 kg/hm<'2>施氮范围内,有效穗数、生物产量、产量、氮素积累总量、最高茎蘖...     

稻草全量还田下氮肥运筹对双季晚稻产量及其氮素吸收利用的影响

【目的】稻草还田和合理的氮肥运筹不仅可以改良土壤和培肥地力,提高农作物产量和品质,还可以减少因过量施用氮肥带来的环境污染。随着水稻机械化收割的快速发展,稻草全量原位还田面积迅速扩大。因此,研究稻草全量还田后合理施用氮肥十分必要。本文通过早稻机收稻草切碎全量还田后晚稻氮肥运筹试验,探索该条件下晚稻氮肥的合理施用技术。【方法】以超级晚稻品种淦鑫688为试验材料,设计4个施氮（N）水平（0、 120、 180、 240 kg/hm2）基蘖穗肥比例为5∶2∶3,并在180 kg/hm2水平下增设稻草不还田对照处理和稻草全量还田下基蘖穗肥不同施氮比例处理（5∶0∶5、 5∶1∶4、 5∶2∶3、 5∶3∶2、 5∶4∶1、 5∶5∶0）。旨在分析不同处理间水稻产量、 产量构成和氮素吸收利用的差异。【结果】稻草全量还田下,施氮量在180 kg/hm2以下时产量随施氮量的增加而增加,之后则下降,处理间差异极显著。随施氮量的增加,有效穗数显著增加,而结实率则显著下降,施氮处理每穗粒数和千粒重显著高于不施氮处理。在相同施氮水平下,因为有效穗数、 结实率和千粒重显著提高,所以稻草全量还田产量极显著高于不还田处理,增幅8.83%。稻草全量还田同一施氮水平下,施氮比例为 5∶2∶3 处理产量极显著高于其他处理,其每穗粒数和千粒重均为最高,有效穗数随分蘖肥比例的增加而减少,处理间结实率差异不显著。稻草全量还田后,随着施氮量增加,其氮素总积累量、 氮肥表观利用率、 氮素的吸收率和百公斤籽粒的需氮量也显著提高,且与施氮量呈极显著正相关。但氮素收获指数和氮肥生理利用率均随施氮量的增加而降低。同一施氮水平下,全量还田处理水稻氮肥农学利用率和生理利用率均显著高于不还田处理。相关分析表明, 氮素总积累量与产量呈二次抛物线极显著正相关,氮肥表观利用率、 氮素吸收率与产量呈极显著正相关。稻草全量还田相同施氮水平下,随着穗肥施氮比例降低,其氮素总积累量、 中期的积累量和比率下降,其氮肥的表观利用率、 收获指数和氮素的吸收率也随之降低,但前期的氮素积累量和比率则升高。氮素的农学利用率和生理利用率均表现为随着穗肥比例的减少呈先增加后降低趋势,均以施氮比例为5∶2∶3处理处理最高,不施穗肥处理最低。各施氮比例处理中,穗肥的施氮量与氮素的总积累量、 中期积累量、 氮肥的表观利用率、 收获指数和氮素吸收率呈极显著正相关,氮肥的农学利用率和生理利用率与产量显著正相关。【结论】稻草全量还田后配施适量的氮肥可以提高晚稻产量,本试验以配施N 180 kg/hm2产量最高;在施纯N 240 kg/hm2以内,施氮越多,氮素积累量越多,相应的氮肥表观利用率、 氮素的吸收率和百公斤籽粒的需氮量也越大。总施氮量相同条件下,以基肥∶分蘖肥∶穗肥为 5∶2∶3 的施氮比例水稻产量, 氮肥农学、 生理利用率均为最高,此结果可作为双季稻区稻草全量还田后的推荐施氮比例。     

Development,growth, and nitrogen use of autumn- and spring-sown facultative wheat

Spring-sown crops are expected to have a higher risk of drought during summer in the next decades in Central Europe due to expected climate change. Therefore, a two-year experiment was conducted under Pannonian growing conditions in Eastern Austria to investigate the effect of autumn- and spring-sowing of facultative wheat. Autumn-sowing of facultative wheat enhanced crop development, soil coverage, crop stand height, crop growth rate, and nitrogen (N) utilization efficiency during the vegetation period compared to spring-sowing; duration of growth stages was prolonged and crops were earlier ripe. In contrast, spring-sowing resulted in higher relative growth rates, higher N concentrations of aboveground dry matter, higher relative N uptake rates, and more mineral N in the soil. At harvest, grain yield and yield components ears m^?2 and thousand kernel weight (TKW) were higher in autumn-sown than in spring-sown wheat, resulting thereby in an increased seed yield. Spring-sown wheat had higher N concentrations in grain and in straw. Anyhow, N yield was slightly higher with autumn-sowing due to the higher grain and straw yields. Grain and straw yield, plant stand height, ears m^?2, and TKW were impaired in the second experimental year by a severe drought for both sowing dates as well as N concentrations and N yields of grain and straw, partial factor N use efficiency and N utilization efficiency. But the yield components harvest index, grains m^?2, and grains ear^?1 were strongly impaired with spring-sowing under drought conditions. Thus, autumn-sowing of wheat resulted in higher yield stability across both years, based on these yield components highlighting possible benefits of autumn-sowing with expected summer drought under climate change.     

Annual warm-season grasses vary for forage yield,quality, and competitiveness with weeds

Warm-season annual grasses may be suitable as forage crops in integrated weed management systems with reduced herbicide use. A 2-year field study was conducted to determine whether tillage system and nitrogen (N) fertilizer application method influenced crop and weed biomass, water use, water use efficiency (WUE), and forage quality of three warm-season grasses, and seed production by associated weeds. Tillage systems were zero tillage and conventional tillage with a field cultivator. The N fertilization methods were urea broadcast or banded near seed rows at planting. Warm-season grasses seeded were foxtail (Setaria italica L.) and proso (Panicum mileaceum L.) millets, and sorghum–sudangrass (Sorghum bicolor (L.) Moench × Sorghum sudenense Stapf.). Density of early emerging weeds was similar among treatments, averaging 51 m^?2. Millets exhibited higher weed density and weed biomass than sorghum–sudangrass. At harvest, sorghum–sudangrass produced significantly greater biomass and N accumulation than either millet. Water use (157 mm) and WUE (25.1 kg mm^-1 ha^?1) of total biomass did not vary among treatments or grass entries. Weed seed production by redroot pigweed and green foxtail was respectively 93 and 73% less in sorghum–sudangrass than proso millet. Warm-season grasses offer an excellent fit in semiarid cropping systems.     

气象要素对陇东塬区玉米产量影响的通径分析

采用通径分析方法分析了陇东塬区玉米产量构成因素中单株籽粒重、百粒重、果穗长、双穗率与光、热、水三要素的关系。结果表明：单株籽粒重和果穗长共同对产量的贡献最大,决定系数为0.3052;其次是单株籽粒重,决定系数为0.2538;果穗长位居第三,决定系数为0.2114。不同发育期各气象因子对单株籽粒重和果穗长影响不同,降水和平均气温在抽雄以前对果穗长和单株籽粒重贡献的直接效应最大;≥10℃积温在播种-拔节期通过平均气温和日照时数对果穗长的贡献以间接效应为主,在拔节-抽雄期对果穗长和单株籽粒重贡献以直接效应为主;日照时数在播种-拔节期对果穗长的影响以直接效应为主,在拔节-抽雄期对果穗长和单株籽粒重的贡献以间接效应为主;抽雄-成熟期各气象要素对果穗长和单株籽粒重影响较小。气象因子对产量构成因素影响主要是在苗期和穗期,灌浆期对其影响明显下降,因此重视田间管理和合理密植等非气象因子也是获取高产的关键。