GAS EXCHANGE AND GROWTH OF TRITICALE SEEDLINGS UNDER DIFFERENT NITROGEN SUPPLY AND WATER STRESS

The effect of nitrogen (30 and 120 mg N per cuvette) on photosynthetic rate of four cultivars of triticale (‘Bolero’, ‘Grado’, ‘Largo’, and ‘Lasko’) grown 14 days in phytotron was strongly modified by water content (75, 45 and 35% of full water capacity). For plants grown under 35% of full water capacity, it was higher when they were grown under 30 than under 120 mg N/cuvette (9.88 and 8.76 μmol CO₂ m^?2 s^?1, respectively) but for plants grown under 45 and 75% of full water capacity there were not significant differences. Transpiration, stomatal conductance, photosynthetic water use efficiency, and internal water use efficiency were not influenced by nitrogen doses independently of water content. Photosynthetic rate, transpiration, stomatal conductance, photosynthetic water use efficiency, and dry matter of studied cultivars of triticale grown under 45 and 35% of full water capacity and both nitrogen doses were lower than for plants grown under 75% of full water capacity. With lowering of water content stomatal conductance was decreasing similarly as photosynthetic rate e.g. for plants grown under 35% of full water capacity as compared with those grown under 75% of full water capacity average stomatal conductance decreased from 0.209 to 0.138 mol H₂O m^?2 s^?1 and photosynthetic rate from 13.69 to 9.32 μmol CO₂ m^?2 s^?1 and as a result there were not significant differences in internal water use efficiency for all studied combinations (67.09 μmol CO₂ mol^?1 H₂O) which shows that stomatal factors were mainly responsible for changes of photosynthetic rate. With lowering of water content from 75 to 35% of full water capacity the decrease of photosynthetic rate and stomatal conductance was much higher than the decreases of transpiration (from 3.57 to 3.02 mmol H₂O m^?2 s^?1) what shows not direct dependence of transpiration on stomatal conductance (water use efficiency decreased from 3.87 to 3.10 μmol CO₂ mmol^?1 H₂O). The effect of nitrogen on dry matter production was strongly modified by water availability e.g. for plants grown under 35% of full water capacity, dry matter was similarly independent of nitrogen dose but for plants grown under 45 and 75% of full water capacity dry matter was significantly higher than when they were grown under 120 (79.05 and 86.75 mg, respectively) or with 30 mg N/cuvette (74.03 and 80.30 mg, respectively).     

NITROGEN RATES AND ITS TIME OF APPLICATION INFLUENCE DRY MATTER PARTITIONING AND GRAIN YIELD IN MAIZE PLANTED AT LOW AND HIGH DENSITIES

Best nitrogen (N) management practices are most important for increasing maize (Zea mays L.) productivity and profitability in Northwest Pakistan. Field experiments were performed at the New Developmental Research Farm of NWFP Agricultural University, Peshawar during summer 2002 and 2003. Factorial experimental treatments were two plant densities (D₁ = 60,000 and D₂ = 100,000 plants ha^?1) and three N rates (N₁ = 60, N₂ = 120 and N₃ = 180 kg N ha^?1) as main plots, and six split N applications in different proportions at different growth stages of maize (cv. ‘Azam’) in two equal, three equal, three unequal, four equal, five equal and five unequal splits at sowing and with first, second, third, and fourth irrigation at two week intervals as subplots. Application of the higher N rate (180 kg ha^?1) with 4 to 5 splits significantly increased leaf, stem, ear, and total plant dry weight at silking and physiological maturity as well as grain yield plant^?1 at both low and high plant densities. Variation in dry matter partitioning and grain yield in maize due to fluctuation in the rainfall data of the two years suggests zonal specific effective N management practices for sustainable maize production in different agro-ecological zones of Northwest Pakistan.     

INVESTIGATION OF SALINITY STRESS AND POTASSIUM LEVELS ON MORPHOPHYSIOLOGICAL CHARACTERISTICS OF SAFFRON

A greenhouse research experiment was conducted to investigate the effect of salinity stress and potassium (K) fertilization on biomass accumulation of roots and shoot of saffron plants. Treatments were four levels salinity in the form of sodium chloride (NaCl; 3.4, 6.4, 9.4 and 12.4 dS m^?1) and three levels of potassium (50, 100, and 150 % of Hoagland's nutrition solution base). Results indicated that higher levels of potassium significantly controlled the negative effects of NaCl on length and number of roots as well as fresh weight and number of leaves per plant. Increase in salinity and potassium levels caused a reduction in leaf water content, and enhancement in electrolyte leakage. It seems that in the presence of salinity increasing 50% extra potassium (Based on Hoagland's nutrient solution) in the rhizosphere of saffron can improve damaging effects of NaCl up to 9.4 dS m^?1 of soil solution.     

施氮水平对甘蔗氮素吸收与利用的影响

以新台糖22号(ROC22)为试材,设15N标记尿素2.5、5.0和7.5g/盆(相当于225、450和675kg/hm2)3个处理,采用网室盆栽试验方式,研究施氮水平对甘蔗氮素吸收与利用的影响。结果表明:甘蔗吸收的氮素17.27%～27.28%来自施用的氮肥,72.72%～82.73%来自土壤和种茎;甘蔗氮肥利用率为34.21%～42.46%。随施氮水平提高,甘蔗干物质积累、氮素积累及来源于肥料氮素的比率显著增加,同时蔗叶对氮素的吸收利用呈上升趋势,但蔗茎对氮素的吸收利用呈下降趋势,氮肥利用率也显著下降。土壤碱解氮和硝态氮在各土层中的含量随施氮水平的提高而增加,且两者在0～20cm土层的积累明显大于20～40cm土层。本试验条件下,甘蔗氮肥施用为尿素5.0g/盆(相当于450kg/hm2)及土层深度为20cm较为适宜。     

RESPONSE OF NON-NODULATING,NODULATING, AND SUPER-NODULATING SOYBEAN GENOTYPES TO POTASSIUM FERTILIZER UNDER WATER STRESS

Soil moisture is a principal environmental factor limiting legume productivity in the tropics and sub-tropics. A pot experiment was conducted at the wire house of National Research Centre, Cairo, Egypt to study how potassium (K) fertilizer can mitigate the adverse effect of water stress. Three Japanese soybean (Glycine max L.) genotypes, non-nodulating (NN) (En 1282), nodulating (N) (Eneri) and super-nodulating (SN) (En-b0-1) were grown under two potassium fertilizer levels (25 and 150 mg kg^?1 soil as K1 and K2, respectively). The water stress (WS) was conducted for eight days. WS significantly reduced nodules numbers and weights, shoot dry weight, relative water content, seed yield, oil, total carbohydrate contents while protein was significantly increased in the three soybean genotypes compared with well-watered (WW). Water stress and/or K treatments caused significant increase in both free amino acids and proline as well as shoot nitrogen in the three soybean genotypes.     

CONTROLLED RELEASE OF FERTILIZER MICROCAPSULES USING ETHYLENE VINYL ACETATE POLYMER TO ENHANCE MICRONUTRIENT AND WATER USE EFFICIENCY

There have as yet been no detailed studies of micronutrient release from polymer coated fertilizers (PCFs). In this research, slow release microcapsules containing iron fertilizer was made and its release pattern evaluated. Three polymers ethyl cellulose (EC), glycerol mono stearate (GMS) and Compritol 888 ATO, were mixed with avicel and lactose and the microcaopsules were made by extrusion/spheronization method. The dissolution test carried out to determine the Fe release rate versus time. The results showed that, microcaopsules containing Compritol 888 ATO, released iron ions slower than that of EC and GMS. The release rate reached 85% after 7 days. In order to reduce the release rate, these microcaopsules were coated with ethylene vinyl acetate (EVA) polymer by dip coating method. It is concluded that the combination of matrix type formulation and the coating with EVA polymer caused a significant decrease in the release rate of iron.     

不同土壤水分供给下水稻叶水势的变化规律

用中9B和金早47在温室及网室条件下,设置4个水分处理,对不同生育期的叶水势进行测定.结果表明,不同水分处理下,主要生育期的叶水势日变化表现为早晨和傍晚较大,而在中午前后较小,呈现反抛物线的曲线走向,中午前后是叶水势曲线拐点.水稻叶水势随着土壤水分含量的下降而降低,土壤保持湿润处理和淹水处理的水稻叶水势差异不明显,而水...     

水分胁迫下AM真菌对甘草生长的影响

利用盆栽试验研究了水分胁迫下接种摩西球囊霉（Glomus mosseae）对甘草（Glycyrrhiza inflata）生长和抗旱性的影响。结果表明,土壤含水量对AM真菌接种效果有显著影响;不同水分条件下,接种AM真菌显著提高了甘草菌根侵染率和全株黄酮以及氮、磷含量。水分胁迫30 d,接种株POD活性和MDA含量显著降低,而土壤含水量为60%和80%时,接种株可溶性蛋白含量显著降低;水分胁迫60d,接种株SOD活性和可溶性蛋白含量显著降低,土壤含水量为60%和80%时,接种株POD活性和可溶性糖含量显著升高,接种株叶绿素含量只在土壤含水量为60 %时显著升高。以胁迫60d土壤含水量为60 %时接种效果最佳。AM真菌可能通过提高宿主植物根系对土壤水分和矿质元素吸收以及改善植物体内生理活动、调节保护酶活性以提高其抗旱性,促进宿主植物生长。     

干旱季节不同耕作制度下作物─红壤水势关系及其对干旱胁迫响应

季节性干旱是南方红壤地区旱地农业生产中的主要障碍因素。本文报道了田间条件下作物土壤水势关系及其对干旱胁迫响应。结果表明ＳＰＡＣ中水势梯度为：叶气系统〉叶土系统〉７０ｃｍ以上土层,且约以１００倍左右递减,水势日变化结果表明免耕较常耕,窄垄较宽垄叶土水势差下降,水分胁迫更强,花生的耐旱性较强,大豆和玉米的则较弱;作物叶水势与土壤基质势呈正相关,可以用二项式表示。作物叶水势与不同土层土壤基质势关系表明,     

A REFLECTANCE-BASED METHOD FOR ESTIMATING TRANSPIRATIONAL WATER USE EFFICIENCY IN MAIZE EXPOSED TO DROUGHT STRESS

A novel measurement technique was developed to remotely sense transpirational water use efficiency (WUE_T). Maize (Zea mays) crop was grown under three water regimes of 0.75, 1.00, and 1.25 times of water surface evaporation (Ep). WUE_T was evaluated and compared with leaf reflectance. Our data showed that drought stress significantly decreased leaf area, leaf water content and WUE_T. Leaf reflectance near the red edge spectrum varied with water regimes and growth stages. Importantly, WUE_T was negatively correlated (P < 0.01) with reflectance near the 760-nm. At the V9 and V12 stages and compared with those of well irrigated treatments, the first derivative reflectance peak of 0.75 Ep was left-shifted to shorter wavelengths. Our study provides an experimental evidence for the red edge - WUE_T relationship, and suggests that reflectance at the 760-nm could be used as a rapid and instant physiological tool to quantitatively assess WUE_T at the leaf level.     

含碎石土壤的含水量测定误差分析

碎石的存在增加了土壤含水量测定的难度,为便于应用,一些学者将碎石当作细土或不透水介质处理,这在一些情况下可能产生很大误差。本文对忽略碎石或其含水量所引起的土石混合介质和细土含水量的误差进行了分析,并用室内实验验证了所得到的结果与相对误差的关系。结果表明,细土和土石混合介质含水量的相对误差与碎石含量以及碎石与细土含水量的比值有关。当碎石与细土含水量比值很大时,即便碎石含量很低也会产生很大误差;而当碎石与细土含水量比值很小时,高的碎石含量同样导致很大误差。此外,碎石与细土含水量的相对大小并非常数,而是随含水量变化的。因此,对土石混合介质田间水分状况的准确监测,以及水分和溶质迁移过程的定量模拟需要考虑碎石特性的影响。     

干旱气候条件下水分胁迫对辣椒叶片生理特性的影响

以"陇椒2号"辣椒为材料,研究了正常水分处理、轻度水分胁迫和中度水分胁迫对辣椒叶片MDA含量、保护酶活性及叶绿素荧光参数的影响,以确定甘肃省干旱气候条件下满足辣椒正常生长的土壤水分。结果表明:随着处理时间的延长,3种处理下辣椒叶片的MDA含量呈上升的趋势,SOD和POD活性均呈现先升高后降低的趋势;中度水分胁迫下辣椒叶片MDA含量和SOD活性均高于另外2个处理,POD活性在处理前期较高,在处理后期则下降;3种处理下辣椒叶片的Fv/Fm、Fv’/Fm’、ФPSII和qP指标均表现出先上升后下降的趋势,在处理后期,中度水分胁迫下的叶片上述指标较低;3种处理下辣椒叶片的NPQ指标变化趋势与qP指标的趋势相反,在轻度水分胁迫下2个指标的变化较为平缓。综合结果说明在水资源相对匮乏的干旱地区,轻度水分胁迫(田间持水量的60%)可以满足辣椒的正常生长需要。     

NUTRIENT UPTAKE,PHYSIOLOGICAL RESPONSES,AND YIELD ATTRIBUTES OF WHEAT (TRITICUM AESTIVUM L.) EXPOSED TO EARLY AND LATE DROUGHT STRESS

The response of different wheat cultivars to drought imposed after three and six weeks of seedling emergence was evaluated in the wire house. The seeds of recommended local wheat cultivars were sown in plastic pots. The drought stress decreased the water relation, nutrient uptake and grain yield of all the wheat cultivars. The early drought stress significantly reduced the nitrogen (N) uptake by 38% while late drought stress decreased nitrogen uptake by 46%. The phosphorus (P) and potassium (K) uptake were decreased by 49% and 37% under early drought stress, respectively while their uptake was decreased by 51% each under late drought stress. Grain yield was reduced by 24% under early drought stress while it was reduced by 60% under late drought stress. Water deficit at early growth stages reduced grain weight by 10% while it was reduced by 35% under water deficit at later stages of growth.     

表层盐化土壤区咸水灌溉试验研究

本文通过田间咸水灌溉试验，研究在不同咸水灌溉条件下，运城盆地湖区灌区土壤水盐运移规律及其对农作物产量的影响，进一步探讨表层盐化土壤区咸水灌溉适宜的灌溉制度。研究结果表明：灌区咸水适宜的灌溉定额为８２５－９７５米＾３／公顷，灌区上游矿化度小于３克／升的微咸水适宜的灌水次数为４次；灌区中游矿化度３－５克／升的咸水适宜的灌水次数为２－３次；灌区下游矿化度５－７克／升的咸水灌水次数最多不能超过１次。该研究     

覆膜不同开孔程度蒸发条件下土壤水热变化动态研究

覆膜灌溉播前铺膜通常无法覆盖全田面 ,而播种后需为作物破土预留出苗孔 ,覆膜灌溉时还需增设灌水孔 ,对上述各类孔的问题 ,可采用覆膜开孔率来统一表征。到目前为止 ,尚未见国内外关于覆膜开孔蒸发的水热耦合迁移方面的报道。在研制了室内蒸发水热动态观测实验系统的基础上 ,本文根据剖面初始含水率均匀的覆膜开孔蒸发土壤水分和温度的动态观测资料 ,分析了土壤温度变化规律及剖面水分的降低趋势 ,并建立了覆膜开孔蒸发的累积蒸发量、相对累积蒸发量及单位膜孔面积累积蒸发量随时间和不同覆膜开孔率变化的函数关系。分析结果表明 ,不同覆膜开孔率控制下的累积蒸发量与时间平方根之间均符合Gardner提出的裸土蒸发理论关系。该结果发展了传统的Gardner方程 ,拓展了该关系的应用途径 ,对今后进一步研究覆膜开孔蒸发的水热运动规律有重要意义。     

土壤水分胁迫对冬小麦氮素分配利用及产量的影响

在防雨棚池栽条件下研究了土壤水分胁迫对冬小麦氮素主产量的影响。结果表明：随土壤水分胁迫加重,植株将吸收的氮素较多地分配于根系,分配于地上部的比率少,肥料氮利用率降低,土壤残留增高,回收率增高,损失率降低,但轻度、中度水分胁迫,有利于氮素向籽粒转移,水分过多,氮素较多地分配至茎叶、鞘等营养器官,较少分配至籽粒,随水分胁迫加重,氮素利用效率降低。底施氮肥利于植株吸收利用,且为土壤固定,损失率较低,所以底施氮肥利用效率高于追施氮肥。因此,在旱作麦田应重视底肥的施用。     

ADAPTING TO CLIMATE CHANGE BY IMPROVING WATER PRODUCTIVITY OF SOILS IN DRY AREAS

Considering extreme events of climate change and declining availability of appropriate quality water and/or highly productive soil resources for agriculture in dryland regions, the need to produce more food, forage and fibre will necessitate the effective utilization of marginal‐quality water and soil resources. Recent research and practices have demonstrated that effective utilization of these natural resources in dry areas can improve agricultural productivity per unit area and per unit water applied. This paper focuses on the following three case studies as examples: (1) low productivity soils affected by high levels of magnesium in soil solution and on the cation exchange complex; (2) degraded sandy soils under rainfed conditions characterized by low water‐holding capacity, organic matter and clay content and (3) abandoned irrigated soils with elevated levels of salts inhibiting growth of income generating crops. The results of these studies demonstrate that application of calcium‐supplying phosphogypsum to high‐magnesium soils, addition of clays to light textured degraded soils and phytoremediation of abandoned salt‐affected soils significantly improved productivity of these soils. Furthermore, under most circumstances, these interventions were economically viable, revealing that the efficient use of marginal‐quality water and soil resources has the potential to improve livelihoods amid growing populations in dry areas while reversing the natural resource degradation trend. However, considerably more investment and policy‐level interventions are needed to tackle soil degradation/remediation issues across both irrigated and dryland agricultural environments if the major challenge of producing enough food, forage and fibre is to be met. Copyright © 2011 John Wiley & Sons, Ltd.     

不同粒径保水剂对土壤物理性质和番茄苗期生长的影响

将不同粒径保水剂拌施土壤,研究其对土壤物理性质的影响及番茄幼苗对其的响应.结果表明,保水剂处理使土壤容重有所降低,略微提高了土壤总孔隙度,与正常水分对照组比较,保水剂处理组的土壤容重平均降低了6.221%,土壤总孔隙度平均提高了4.417%;土壤质量含水量、田间持水量、地上和地下部分干重都高于干旱对照组但低于正常水分对...     

EFFECT OF SALINIZATION OF SOIL ON GROWTH,WATER STATUS AND NUTRIENT ACCUMULATION IN SEEDLINGS OF ACACIA AURICULIFORMIS (FABACEAE)

Greenhouse experiments were conducted to assess the effects of salinization of soil on emergence, growth, water status, proline content, and mineral accumulation of seedlings of Acacia auriculiformis A. Cunn. ex Benth. (Fabaceae). Sodium chloride (NaCl) was added to the soil and salinity was maintained at 0.3, 3.9, 6.0, 7.9, 10.0, 12.1, and 13.9 dS m^?1. Salinity caused reduction in water potential of tissues, which resulted in internal water deficit to plants. Consequently, seedling growth significantly decreased with increase in soil salinity. Proline content in tissues increased with increase in salinity. Potassium and sodium content significantly increased in tissues as salinity increased. Nitrogen content significantly increased in tissues with salinization of soil. Phosphorus, calcium and magnesium content significantly decreased as salinity increased. Changes in tissues and whole-plant accumulation patterns of other nutrients, as well as possible mechanisms for avoidance of sodium toxicity in this tree species in response to salinity, are discussed.     

Growth Responses of Maize Plants Cultivated in Sandy Soil Amended by Different Superabsorbant Hydrogels

The growth responses of maize plants cultivated in sandy soil amended with five different superabsorbent hydrogels were studied. Soil amended by superabsorbent hydrogels could enhance growth of maize and the level of enhancement was concomitant with the rate of the added hydrogel. Morphologically, plants grown in soil with the highest concentration of hydrogel (0.4%) were healthier and taller, and root lengths were longer. Fresh and dry weights were increased. Addition of hydrogel could improve water availability in the soil, so that water contents were higher in plants grown in the amended soil compared with those of control. Although maize growth was enhanced by the addition of any hydrogel, plants showed different responses to different hydrogels. The used hydrogels were beneficial in newly reclaimed deserts that suffered from drought stress conditions.