Management practices to control premature senescence in Bt cotton

Commercial cultivation of Bt cotton produced higher boll load which led to stiff inter-original competition for photosynthates, resulting in early cessation of growth (premature senescence) due to more availability of sink and less sources. To overcome this problem, field experiment was conducted during 2011 and 2012 using five treatments of plant growth manipulation viz. no fruiting branch removal (F₁), removal of first fruiting branch (F₂), removal of first and second fruiting branch (F₃), removal of all squares from first fruiting branch (F₄), removal of all squares from first and second fruiting branches (F₅), and three potassium (K) application rates viz. 50 kg ha^?1 (K₁), 100 kg ha^?1 (K₂), and 150 kg ha^?1 (K₃). More nodes above white flower were recorded in F₅, followed by F₃, while minimum were recorded in F₁. Among potassium levels, maximum nodes above white flower were recorded in K₃ followed by K₂ and K₁ during both years of study. Plant height recorded at physiological cutout stage or at maturity stage showed that plants gained more height with removal of all squares from first tosecond fruiting branches with higher potassium dose. Leaf K increased with increasing applied potassium and also with square/branch removal. So early removal of squares/fruiting branches along with higher potassium dose helped in delaying canopy senescence in Bt cotton.     

Nitrogen management improves lodging resistance and production in maize (Zea mays L.) at a high plant density

Lodging in maize leads to yield losses worldwide. In this study, we determined the effects of traditional and optimized nitrogen management strategies on culm morphological characteristics, culm mechanical strength, lignin content,root growth, lodging percentage and production in maize at a high plant density. We compared a traditional nitrogen(N) application rate of 300 kg ha–1(R) and an optimized N application rate of 225 kg ha^–1(O) under four N application modes: 50% of N applied a...     

不同土壤水分调控技术对土壤含水量和鸭梨果实品质的影响

以13、20和30年生鸭梨为试材,分别在辛集市新垒头、泊头市苗圃场和曲阳县寺南庄梨园,研究了覆膜、定期浇水和对照3种不同土壤水分调控技术对土壤含水量和鸭梨品质的影响。结果表明,土壤含水量以定期浇水最高,对照和覆膜较低;平均单果重以定期浇水最大,覆膜次之,对照最小;果肉硬度则正相反;可溶性固形物、总糖含量和糖酸比以对照最高,覆膜次之,定期浇水最低;可滴定酸含量以定期浇水最高,对照和覆膜较低;Vc含量以覆膜最高,对照次之,定期浇水最低;果实淀粉和果皮叶绿素含量均表现为对照>定期浇水>覆膜。     

保护性耕作下西南旱三熟农田土壤水分动态及产量效应

以西南地区麦/玉/薯三熟制种植模式为研究对象,研究了不同保护性耕作模式下旱地土壤水分动态变化、水分利用效率、作物产量和经济效应。结果表明,不同保护性耕作对整个农田生态系统产量和水分利用效率具有显著影响。秸秆覆盖(TS)、地膜覆盖(TM)、秸秆覆盖+地膜覆盖(TSM)和垄作+秸秆覆盖+地膜覆盖(RSM)能改善7,10月份0—60cm土层土壤含水量及贮水量,而垄作(R)、垄作+秸秆覆盖(RS)和垄作+地膜覆盖(RM)的作用不明显。与平作(CK)相比,RSM,RM,RS,TSM,TM,TS和R分别使系统增产10.52%,6.11%,6.77%,4.59%,5.12%,3.15%,1.24%。这些处理对水分利用效率和降水利用效率的增幅分别为1.26%～11.08%,1.27%～10.57%。研究结果说明,从WUE、降水利用效率、产量效应、经济效益这4个方面来看,垄作+秸秆覆盖+地膜覆盖耕作模式综合效益最佳。     

Effects of nitrogen and water stress on the rehydration,endogenous hormonal regulation and yield of maize

Water scarcity is known to be a strong limiting factor affecting maize grown and yield in cold semi-arid regions. Numerous studies have shown that rehydration improves maize growth. Our study aimed to explore the effects of rehydration treatments on maize growth and yield under water and nitrogen stress during different growth stages. We selected the drought-tolerant maize variety Nendan 19 (ND19) and subjected it to water stress during the V6 (sixth-leaf), R2 (filling) and R6 (maturity) growth stages and a rehydration treatment after each stress stage. Our results indicated that N1 (N100 kg N ha⁻¹) and N3 (N300 kg N ha⁻¹) treatments significantly increased the leaf moisture status relative to water content (RWC), bound water content (BWC), free water content (FWC) and water potential (WP)) at different growth stages. Similar trends were observed in the accumulation of plant leaf and root hormones (zeatin+zeatin riboside, indole-3-acetic acid, abscisic acid and gibberellic acid), photosynthetic pigments and chlorophyll fluorescence. However, under the same water stress conditions, they decreased as the N rate increased and reached a minimum value in the S3 (water stress for N3) treatments. In addition, with growth stage advancement and extension of the rehydration time, both showed a gradual upward trend. The results showed that to save water resources in the cold semi-arid region, rehydration treatments (R2S1 and R2S3) significantly increased the photosynthetic pigments and chlorophyll fluorescence parameters, leaf moisture status, biomass, 100-grain weight, hormone content, ear characteristics and grain yield of maize.     

Perspectives of Using L-Tryptophan for Improving Productivity of Agricultural Crops: A Review

Plant growth regulators are biologically active signaling molecules that regulate a number of plant physiological processes. Auxin (indole-3-acetic acid) is an important plant growth regulator and is synthesized within plant tissues through L-tryptophan (L-TRP)-dependent and -independent pathways. It has been found that plants respond to exogenously applied L-TRP due to insufficient endogenous auxin biosynthesis. The exogenous application of L-TRP is highly significant for normal plant growth and development. L-tryptophan is applied through foliar spray, seed priming, and soil application. Soil-applied L-TRP is either directly taken up by plants or metabolized to auxin by soil microbiota and then absorbed by plant roots. Similarly, foliar spray and seed priming with L-TRP stimulates auxin synthesis within plants and improves the growth and productivity of agricultural crops. Furthermore, L-TRP contains approximately 14% nitrogen (N) in its composition, which is released upon its metabolism within a plant or in the rhizosphere and plays a role in enhancing crop productivity. This review deals with assessing crop responses under the exogenous application of L-TRP in normal and stressed environments, mode of action of L-TRP, advantages of using L-TRP over other auxin precursors, and role of the simultaneous use of L-TRP and auxin-producing microbes in improving the productivity of agricultural crops. To the best of our knowledge, this is the first review reporting the importance of the use of L-TRP in agriculture.     

Effect of Fruiting Branch/Square Removal on Growth and Quality of Bt Cotton under Different Potassium Rates

Removal of early fruiting branches with greater potassium doses caused more source and no sink at early stages of growth, leading to improved yield, yield components, and fiber quality traits in Bt cotton. The study used manual alteration of plant architecture (F₁, no branch removal; F₂, removal of first fruiting branch; F₃, removal of first and second fruiting branches; F₄, removal of all squares from first fruiting branch; F₅, removal of all squares from first and second fruiting branches) and potassium rates (50, 100, and 150 kg ha^?1) in a randomized complete block design and was repeated for 2 years (2011 and 2012). Increasing potassium application increased total bolls per plant and cotton yield to the greatest levels in F₃ and F₅, against lowest level in the control. Ginning out turn, fiber length, seed oil, and seed protein content were influenced by fruiting branch or square removal but the difference was less. Increasing potassium improved seed and fiber quality.     

基于能值生态足迹模型的高温伏旱区生态安全研究——以重庆市江津区为例

随着全球环境恶化的速度加快,区域生态安全问题日益突出,特别是对高温伏旱区的生态安全的研究需求越来越迫切。本文利用基于能值理论改进的生态足迹模型,对重庆市江津区2002~2007年的生态安全现状做了全面评估。结果表明:(1)2002~2007年江津区均处于较安全等级,但是安全等级程度逐年下滑,因此需要密切关注;(2)在2002年之后,江津区一直处于强不可持续状态,程度呈逐渐加深的态势。