The effect of C/N ratio on bacterial community and water quality in a mussel‐fish integrated system

A 30‐day experiment was conducted to evaluate the effect of C/N ratio on water quality and bacterial community in an integrated system comprising one molluscan species (pearl mussel Hyriopsis cumingii) and two fish species (gibel carp Carassius gibelio and silver carp Hypophthalmichthys molitrix) at five C/N ratios (6, 8, 10, 12 and 14). The mussel and fishes were reared in the experimental tanks (400 L), but gibel carp received formulated feed. Water quality in the experimental tanks was analysed on day 0, 10, 20 and 30, and bacterial community in the water column and sediment was analysed on day 30. Total nitrogen, total phosphorus and total organic carbon accumulated in the tanks over time. Ammonia and nitrite decreased with the increase in C/N ratio. Bacterial community in the water column and sediment changed at the phylum and genus levels with the increase in C/N ratio, and the critical C/N ratio causing a functional shift of bacterial community occurred at 10 in water column and 12 in sediment. The increase in C/N ratio benefited the growth of both potential probiotics and pathogenic bacteria. The high C/N ratio enhanced the bacterial functions of chemoheterotrophy and hydrocarbon degradation, but depressed the functions of nitrification and denitrification in the water column and sediment respectively. This study reveals that the C/N ratio can be used as a tool to manipulate the bacterial community and water quality in the mussel‐fish integrated system.     

Replacement of de‐oiled rice bran by soaked and fermented sweet potato leaf meal: Effect on growth performance,body composition and expression of insulin‐like growth factor 1 in Labeo rohita (Hamilton), fingerlings

A 60‐day feeding trial was conducted to determine the growth performance and expression of insulin‐like growth factor 1 gene (IGF‐I gene) in Labeo rohita fingerlings fed with either raw, soaked or fermented sweet potato leaf meal (SPLM) by completely replacing de‐oiled rice bran (DORB), following a completely randomized design. Seven isonitrogenous (30%) and isocaloric (1.8 MJ/100 g) diets were prepared by replacing DORB with 50% and 100% raw, soaked and fermented sweet potato leaf meal, maintaining DORB‐containing diets as a control. Weight gain %, SGR (specific growth rate) and PER (protein efficiency ratio) were significantly (p < 0.05) higher when 100% DORB was replaced by fermented SPLM in comparison to other treatment groups. The fermented and soaked SPLM‐fed groups had registered with lower FCR value. The expression of growth regulating gene IGF‐I mRNA and RNA/DNA ratio was found to be significantly higher (p < 0.05) in soaked and fermented SPLM‐fed groups. In this study, the body protein and lipid composition did not vary significantly (p > 0.05). Hence, the study concludes that the fermented sweet potato leaf meal using Chaetomium globosum can replace 100% DORB in the diet of Labeo rohita without any detrimental effect on growth performance.     

膜下滴灌棉田生物改良盐碱地效果研究

通过在膜下滴灌棉田间作苜蓿(Ⅰ)、孜然(Ⅱ)和碱蓬(Ⅲ),并以未间作的处理作为对照(CK),研究不同盐生植物改良盐碱地的效果。结果表明：间作盐生植物的棉田在生育期内可以达到保水和抑制盐分累积的效果,土壤含水量峰值基本保持在40 cm深度,其中以间作苜蓿(Ⅰ)和孜然(Ⅱ)的保水效果较好,在0～40 cm深度范围土壤含水量与对照组相比分别提升了29.80%和14.49%;间作苜蓿(Ⅰ)和孜然(Ⅱ)的处理抑制盐分累积的效果也较好,在0～40 cm深度范围抑盐率分别为125%和70.38%。同时,通过在膜间种植盐生植物,棉花的株高、茎粗和干物质量均有一定程度的增加,籽棉产量也有相应的提升,其中以间作孜然和苜蓿的处理提升较多,分别比对照组提升10.45%和7.74%。由此可见,膜下滴灌棉田间作盐生植物是一种有效的盐碱地改良措施,而盐生植物的选择对改良的效果影响较大,综合试验结果对比,间作孜然和间作苜蓿的生物改良措施效果较好。     

饲养密度和性比对蠋蝽存活和繁殖生物学特性的影响

蠋蝽是优良的捕食性天敌昆虫,可捕食40余种重要害虫。为明确成虫不同的性别配比和饲养密度对蠋蝽的寿命、繁殖力和后代生长发育的影响,促进蠋蝽的规模化饲养,在室内测定了不同性别配比（雌/雄为4F/2M、3F/3M、2F/4M、6F和6M）和密度（雌/雄为4F/2M和2F/1M;3F/3M、2F/2M和1F/1M）的蠋蝽的存活率、产卵量、无效卵的比例以及后代发育速率和性比等指标。结果显示,不同饲养密度和成虫性别配比对蠋蝽的存活率、产卵量、有效卵的孵化率以及无效卵的比例均有显著影响,但对后代的发育速率和性比无显著影响。2F/2M的蠋蝽30 d内存活率最高（65%）,且无效卵的比例最低（12.68%）,单头雌成虫30 d内产卵量为105.5粒,与产卵量最高的处理1F/1M无显著差异。4F/2M的蠋蝽的卵孵化率最高,为88.05%,但是与2F/2M（81.57%）无显著差异。2F/2M的蠋蝽适合度指数最高（441.14）,而3F/3M的适合度指数最低。结果表明,在高10 cm,直径7 cm的透明塑料杯内饲养蠋蝽成虫时,雌、雄成虫最佳饲养密度和性别配比为2F/2M。选用合适的饲养密度和性别配比可显著提高蠋蝽成虫的繁殖力。     

Box-Behnken 设计 - 响应面法优化感应静电喷雾参数

为了探究静电喷雾过程中多因素对荷质比的影响,采用感应荷电方式,先对4种孔径喷嘴的荷质比进行试验,选取一个荷质比变化较显著的喷嘴,然后采用单因素试验方法,分别对充电电压、喷雾压力、药液电导率3个因素进行试验,探讨各因素对荷质比的影响规律。在此基础上采用Box-Behnken设计-响应面法以TXVK-3型喷嘴的充电电压、喷雾压力、药液电导率进行3因素3水平的优化试验,确定最优参数。结果表明,在电压6.9 kV、喷雾压力0.3 MPa、药液电导率13.9 mS/cm时,平均荷质比为-0.227 mC/kg,相对误差不到2%。     

不同施肥处理对棉花生长及产量参数的影响

通过研究不同施肥处理下棉花株高、净光合速率、蕾铃脱落率、根冠比在不同生育期内的动态变化特征,分析不同施肥处理对棉花产量参数的影响。结果表明:在一定范围内(N≤360 kg/hm~2,P≤180 kg/hm~2)增施氮磷钾肥均能促进棉花生长速度的加快,其中处理N3P2的生长速度比处理N_0P_2、N_1P_2和N_2P_2分别快18.49%、12.61%和3.07%,增施钾肥可以促进棉花在生育后期的生长。在棉花整个生育期,净光合速率(Pn)是波动的,随着氮素水平从N_1增加到N_3,净光合速率增加,而磷肥的不同施用量对棉花净光合速率(Pn)的影响不明显。与对照相比,施肥处理显著降低了棉花的蕾铃脱落率,使有效铃数显著提高,其中处理N_3P_2的棉花蕾铃脱落率比处理N_0P_2、N_1P_2和N_2P_2分别降低2.64%、1.81%和0.88%,有效铃数分别提高3.0、2.5、1.34个/株;其中处理N_2P_3的棉花蕾铃脱落率比处理N_2P_0、N_2P_1和N_2P_2分别降低2.53%、1.80%和0.71%,有效铃数分别提高2.0、1.5、1.77个/株。在所有施肥处理中,处理N_3P_2的有效铃数最高、为8.67个/株,处理N_2P_2K_2蕾铃脱落率最低、为59.65%。氮磷肥表观利用率、农学利用效率、肥料贡献率以及增产效益均随施氮磷量的增加而逐渐升高,说明合理配施氮磷钾肥可以有效促进棉花生长,提高肥料利用率,且可以提高棉花产量,表现出较好的经济效益。     

小型水稻联合收割机旋风分离清选装置的结构优化与试验

旋风分离清选装置具有体积小、重量轻、结构简单等优点,现已广泛应用于小型水稻联合收割机。但其清选过程中仍存在损失率高、湿物料清选效果不佳等问题,通过对旋风分离筒内部结构进一步优化与改进,并运用Fluent 15.0软件对优化前后的分离筒内部气流场进行了比较分析。以吸杂风机转速、扬谷器转速、挡板倾斜角度为试验因素,清洁率和损失率为性能评价指标,运用三元二次正交试验方法进行了台架试验,试验结果表明：当吸杂风机转速为2 452 r/min,扬谷器转速为783.8 r/min,挡板倾斜角度为41°时,装置性能最佳,此时清洁率为98.26%,损失率为0.003 5%。对照试验结果表明：脱出物含水率越高,装置优化后性能提升效果越明显,该结果可为后期旋风分离筒结构优化设计提供参考。     

鲜食糯玉米/大豆间作模式及经济效益分析

该研究主要分析糯玉米/大豆间作对鲜食糯玉米及鲜食大豆的产量及主要农艺性状的影响及该模式的经济效益.结果表明,虽然间作糯玉米和大豆的鲜产分别较单作下降21.20％、31.05％,但间作土地当量比(1.48)大于1,表明该模式能够有效提高土地利用率.糯玉米/大豆间作对糯玉米的多数性状有提高作用,而大豆的多数性状则有下降趋势.各模式经济效益从高到低依次是:糯玉米/大豆间作、糯玉米单作、大豆单作.     

台湾桤木轻基质容器育苗技术(英文)

台湾桤木轻基质无纺布容器育苗技术是容器育苗先进技术。轻基质容器苗具有生长好、成本低、周期短、造林成活率高等优点,且能进行工厂化、标准化生产。基于多年的台湾桤木育苗经验,该文从种子采集、芽苗培育、容器苗培育等关键环节进行了阐述,为台湾桤木壮苗培育和规模化生产提供技术支撑。     

块状紫山药新品种苏蓣2号选育及全程机械化栽培技术

利用辐射诱变育种技术筛选出优质、高效、专用并适于全程机械化栽培的块状紫山药新品种———苏蓣2号。农机、农艺融合,应用苏鲁2个厂家生产的4种机械可完成旋耕、起垄、播种、中耕、追肥、施药、除草、培土、切蔓和收获等10种主要生产工序。单件机械的作业效率为4~5 hm2/d,山药主产区、特菜区节本增效为3.75万元/hm2以上。该全程机械化栽培技术操作简单,切实可行,易于推广。