Nitrogen fertigation of greenhouse-grown cucumber

Summary This greenhouse study investigated the response of trickle-irrigated cucumber (Cucumis sativa cv. ‘Petita’) to three N levels applied with every irrigation via the irrigation stream. The plants were grown in pots filled with 12 kg of soil. Water containing 5.8, 11.8, or 17.8 mmol N/l, and uniformly supplied with 2.0 and 3.9 mmol/l of P and K, respectively, was applied two to three times daily. In all treatments of 0.3 leaching fraction was allowed. The resulting total N applications were 15.7, 31., and 47.2 g N/plant. The total amount of water applied was 1851/plant. Total N and NO₃-N, in lajinae and petioles, increased with increasing N level whereas P and K in generated decreased. Although different NO₃/NH₄ ratios in the treatments may have influeced the response to N, it could be concluded that the highest yield was obtained with 11.8 mmol N/1 due to increased number of fruit. In the root volume of this treatment the NO₃-N concentration in the soil solution was aroun 7 mmol/1 for most of the growing season. The dry matter concentration of fruits was not affected by the N levels. It was concluded that 11.8 mmol N/1 applied with every irrigation via the irrigation stream is adequate to cover the needs of greenhous-grown cucumber for higher yield (9.42 kg/plant over a harvesting period of 93 days).     

Passive irrigation and functional morphology of crustacean burrows in a tropical mangrove swamp

Flushing measurements and a resin cast of a burrow inhabited by Sesarma messa and Alpheus cf macklay were taken from a Rhizophoraspp. forest. The burrow had 9 openings and occupied a swamp surface area of 0.64 m². Passive irrigation of the burrow was investigated by recording change in conductivity of burrow water in a chamber 45 cm below the swamp surface during tidal inundation of the swamp. The chamber was completely flushed within approximately one hour, i.e. by a single tidal event. Burrow morphology was determined by means of resin casting. The investigated burrow was of discrete structure, with an overall depth of 1.2 m and a total volume of 68 l, i.e. ca. 9% of the volume of swamp soil. The below ground surface area of chambers and tunnels was 3.8 m². The mean and maximum chamber/tunnel diameter was 7 cm and 11 cm respectively. The soil in the close vicinity of the burrow was extensively penetrated by roots, and any two parts of the burrow were located no further than 20 cm away from each other. By reducing diffusion distances within the soil and by being well flushed, the burrows provide an efficient mechanism for removal of excess salt accumulated in the soil around mangrove roots due to exclusion.     

Use of Avermectins for the Control of Meloidogyne incognita on tomatoes

The efficacy of avermectins B₁ and B₂ for control of Meloidogyne incognita on tomato was studied in pots and field plots for two seasons. Avermectins were applied as granules and liquid in furrows or by low pressure drip irrigation systems, at rates ranging from 0.093 to 0.34 kg a.i./ha, as single or multiple applications. Levels of control comparable to those obtained by oxamyl and aldicarb at 3.36 kg a.i./ha were achieved by the avermectin with only 1/10 the volume of chemicals applied to the environment. Avermectin protection of the roots remained constant throughout the first 5 weeks giving slightly longer protection than oxamyl or aldicarb.     

Irrigation planning to transform subsistence agriculture: Lessons From El Salvador

Experience with irrigation schemes designed to improve the productivity of subsistence farmers in Latin America seems to parallel the results of the green revolution in Southeast Asia. Although in some cases the impact on the productivity has been significant, in far too many cases the pervasive pattern of inequity has been reinforced. This case study of the Irrigation District of Zapotitan in El Salvador analyses some of the reasons for the unexpected results, with particular reference to the planning process. It essentially illustrates that the transformation of subsistence agriculture through irrigation demands new institutions designed not only to service agricultural production but also to ensure the accrual of benefits on the targeted group.     

Carbon isotope discrimination at vegetative stage as an indicator of yield and water use efficiency of spring wheat (Triticum turgidum L. var. durum)

A field experiment was conducted to investigate if carbon isotope (¹³C) discrimination () measured at the vegetative stage of spring wheat (Triticum turgidum L. var. durum) is related with the yield and water use efficiency (WUE) at ripening. A line source sprinkler irrigation system exposed the wheat genotypes to different watering regimes, from rainfed to full irrigation and thereby increased the range in yield and WUE attainable in the four genotypes studied. The results indicated that values measured at the late stem elongation stage 60 days after planting (DAP), showed strong positive correlation with total dry matter yield (r=0.732^***), and a highly significant negative correlation with WUE (r=–0.755^***) measured at ripening 105 DAP. The data suggest that the imprints of measured at vegetative growth stage persists throughout the entire growth period, until maturity. Subject to confirmation from additional studies in other crops and locations, early measurements of may prove a useful tool for rapid and early screening of cultivars, for high yield and high WUE.     

高浓度臭氧对蒙古栎叶片酚类物质含量和总抗氧化能力的影响

采用开顶箱(OTC)法,研究了高浓度臭氧(80±8 nmol·mol^-1)熏蒸处理对蒙古栎叶片 中总酚、类黄酮、单宁及丙二醛(MDA)含量的影响,使用1,1-二苯基苦基苯肼(DPPH) 法测定了蒙古栎叶片的总抗氧化能力.结果表明:蒙古栎叶片中总酚、类黄酮、缩合单宁和MDA的含量都有所增加,其中总酚和缩合单宁含量分别增加了48.17%和26.77%,差异显著（P<0.05）;类黄酮和MDA含量分别增加了24.66%和5.26%,差异不显著(P＞0.05);蒙古栎叶片总抗氧化能力显著增强(P<0.05),且与叶片中总酚和缩合单宁含量呈显著的正相关关系.     

群体分布和灌溉对冬小麦农田光能利用的影响

于2006-2008年进行冬小麦田间试验,设置行距×株距分别为：7 cm×7 cm（A）、14 cm×3.5 cm（B）、24.5cm×2 cm（C）、49 cm×1 cm（D）4种群体分布方式,每种分布方式设4种灌溉处理：整个生育期内不灌溉,灌拔节水,灌拔节和抽穗水,灌拔节、抽穗和灌浆水（每次灌水量相同,均为0.60 m³）,研究在同一群体密度(2.04×10⁶ 株·hm^-2)下不同群体分布和灌溉对冬小麦光能利用状况的影响及其在生产中的利用价值.结果表明：A、B处理的群体分蘖数和叶面积指数（LAI）显著高于C、D处理;随着行距的加大,光合有效辐射（PAR）透射率逐渐增多,而PAR截获率呈下降趋势;增加灌溉可提高冬小麦群体单茎数和LAI,降低PAR透射率,从而明显提高了PAR总截获率.冠层内PAR截获率表现为上强下弱的趋势,相对均匀的群体分布和所有灌溉处理均显著增加了冠层40 cm以上的PAR截获率.冬小麦光能利用率（RUE）随行距增大而逐渐降低,其中,A、B、C、D处理总RUE两年的均值分别为1.24%、1.27%、1.21%和1.06%,B处理较C、D处理分别提高了5.21%和19.56%,差异显著.群体分布相对均匀的A、B处理可显著改善冬小麦群体结构和PAR截获状况,有利于充分利用光能;所有灌溉处理也可影响群体结构,进而明显提高作物的RUE.     

宁夏引黄灌区秸秆还田对麦田土壤硝态氮淋失的影响

以宁夏引黄灌区为例,探索秸秆还田条件下冬小麦土壤硝态氮淋失规律。试验设置常规施肥(CK)、常规施肥条件下施用4500kg/hm2(T1,半量还田)和9000 kg/hm2(T2,全量还田)秸秆3个处理。利用树脂芯法吸附10、20、30、60cm和90cm土层的硝态氮流失量。结果表明:硝态氮(纯N)淋失量6.26—12.85 kg/hm2,是冬小麦施用化肥氮量的2.78%—5.71%。与对照CK相比,T1和T2在10cm土层减少0.09%和3.97%;20cm土层减少8.51%和9.81%;30cm土层减少2.25%和10.34%;60cm土层减少23.85%和13.08%;90cm土层减少27.65%和20.73%。10cm和20cm土层,处理与对照以及处理之间均未到显著性差异(P0.05);30cm处理,T1与CK以及T1与T2未达到显著性差异,但T2与CK达到显著性差异表明全量还田效果最好;60cm土层,处理与对照、以及处理之间均达到显著性差异;90cm土层,处理与对照之间达到显著性差异,处理之间未达到显著性差异。硝态氮淋失主要发生在冬小麦返青至灌浆期间,占全生育期淋失量的52.95%—67.79%。T1、T2冬小麦产量增产率分别为10.11%与11.51%。可见,稻秆还田能够减少灌区土壤硝态氮淋失量。     

测墒补灌对冬小麦氮素积累与转运及籽粒产量的影响

2007-2009年,在田间条件下,以冬小麦品种济麦22为材料,以0-140 cm土层平均土壤相对含水量为指标设计4个测墒补灌试验处理:W0(土壤相对含水量为播种期80%+拔节期65%+开花期65%)、W1(土壤相对含水量为播种期80%+拔节期70%+开花期70%)、W2(土壤相对含水量为播种期80%+拔节期80%+开花期80%)和W3(土壤相对含水量为播种期90%+拔节期80%+开花期80%),研究不同水分处理对冬小麦氮素积累与转运、籽粒产量、水分利用效率及土壤硝态氮含量的影响。结果表明:(1)成熟期小麦植株氮素积累量为W1处理最高,W3处理次之,W0和W2处理最低,W0和W2处理间无显著差异;氮素向籽粒的分配比例为W2处理显著低于W1处理,W0、W1、W3处理间无显著差异。开花期和成熟期营养器官氮素积累量、营养器官氮素向籽粒中的转移量、成熟期籽粒氮素积累量均为W1>W3>W2>W0,各处理间差异显著。(2)随着小麦生育进程的推进,0-200 cm土层土壤硝态氮含量先降低后回升再降低,在拔节期最低。成熟期W0和W1处理0-200 cm土层土壤硝态氮含量较低,W2和W3处理120-200 cm土层土壤硝态氮含量较高。(3)W0处理小麦氮素吸收效率、利用效率和氮肥偏生产力最低;随灌水量的增加,氮素利用效率呈先升高后降低趋势;W1处理小麦对氮素的吸收效率和利用效率较高,氮肥偏生产力最高。W0处理水分利用效率较高,但籽粒产量最低;灌水处理籽粒产量、灌溉水利用效率和灌溉效益两年度均随测墒补灌量的增加而显著降低。在本试验条件下,综合氮素利用、籽粒产量、灌溉水利用效率及土壤中硝态氮的淋溶,W1是高产节水的最佳灌溉处理,在2007-2008年和2008-2009年度补灌量分别为43.83 mm和13.77 mm。