Dietary threonine requirement of fingerling Indian major carp,Labeo rohita (Hamilton)

An 8‐week feeding experiment was conducted in a water flow‐through system (26–28 °C) to determine the dietary threonine requirement of fingerling Labeo rohita (3.90±0.03 cm; 0.58±0.02 g). Growth, feed utilization and body composition of fish fed test diets (40% crude protein; 17.9 kJ g^?1 gross energy) with graded levels of l ‐threonine (0.75%, 1.0%, 1.25%, 1.50%, 1.75% and 2.0% dry diet) to apparent satiation were response variables used to assess threonine adequacy. Diets were made isonitrogenous and isoenergetic by adjusting the levels of glycine and dextrin. The amino acid profiles of the test diets were formulated to that of 40% whole chicken egg protein except for threonine. The performance of fish fed experimental diets was evaluated using calculated values for weight gain (g fish^?1), feed conversion ratio (FCR), protein efficiency ratio (PER) and protein productive value (PPV) data. Maximum weight gain (g fish^?1) (1.79), lowest FCR (1.39), highest PER (1.76) and PPV (0.33) were recorded at 1.50 g per 100 g dietary threonine. Statistical analysis of weight gain, FCR, PER and PPV data reflected significant differences (P<0.05) among treatments. Except for reduced growth performance in fish fed threonine‐deficient diets, no deficiency signs were noted. Weight gain, FCR, PER and PPV data were also analysed using second‐degree polynomial regression analysis to obtain a more accurate threonine requirement estimate, which was found, using each response variable, to be at 1.70, 1.63, 1.65 and 1.51 g per 100 g of dry diet, corresponding to 4.2, 4.07, 4.12 and 3.77 g per 100 g of dietary protein respectively. Based on the second‐degree polynomial regression analysis of the live weight gain, FCR, PER and PPV data, the optimum dietary level of threonine for fingerling L. rohita was found to be in the range of 1.51–1.70 g per 100 g of the dry diet, corresponding to 3.77–4.2 g per 100 g of dietary protein.     

基于临界氮浓度稀释曲线的小麦氮肥需求量估测研究

为探究基于临界氮浓度稀释曲线估测小麦氮素需求量的可行性,基于不同生态区开展的不同品种及氮肥水平的小麦试验,结合小麦临界氮浓度曲线(N_c=4.16W~(-0.41)),构建了拔节期、孕穗期、抽穗期和开花期四个关键生育时期下,小麦氮营养指数(NNI)、氮素需求量(NR)及相对产量(RY)三者间的关系模型,并进行了验证。结果表明,在江苏地区,当总施氮量在120～180kg·hm~(-2)时,小麦的氮素需求量最接近于0,氮营养指数最接近于1,为最优的氮素施用量。氮营养指数与氮素需求量(NNI-NR)在小麦生长的各关键阶段存在极强的线性关系(R~2=0.93～0.97);相对产量与氮营养指数(RY-NNI)在各生育时期呈现线性加平台关系,在开花期表现最好,R~2=0.86;相对产量与氮素需求量(RY-NR)的拟合关系在抽穗期表现最好,R~2值为0.72。NNI-NR验证结果与建模结果一致,即在各时期均表现良好,其中拔节期相关关系最强;但RY-NNI和RY-NR验证结果显示两模型分别在开花期和抽穗期预测效果表现最佳。综上,所构建的NNI-NR、RY-NNI和RY-NR三种模型均具有良好的拟合优度和稳定性,运用基于临界氮浓度曲线的小麦氮营养指数和确立的相对产量水平,可以较好地估测当季的小麦氮素需求量,并进行小麦田间氮素精确管理。     

Effects of dietary phosphorus level on non-faecal phosphorus excretion from yellowtail (Seriola quinqueradiata Temminck & Schlegel) fed purified and practical diets

Non-faecal phosphorus (P) was determined for large yellowtail to estimate a minimum available P requirement (Experiment  1) and to justify inorganic P supplementation in a fish meal-based diet (Experiment 2). In Experiment 1, purified diets with incremental P concentrations were fed to yellowtail (mean weight 917 g) at a feeding rate of 1.5% of body weight. The peaks of non-faecal P excretion appeared 5–6 h after feeding in fish fed more than 4.5 g available P kg⁻¹ dry diet. Broken-line analysis indicated that the minimum available P requirement was 4.4 g kg⁻¹ dry diet. In Experiment 2, a purified diet (PR) containing 6.5 g available P kg⁻¹ and a fish meal-based diet with (F1) and without (F0) additional phosphorus were fed to yellowtail (mean weight 1.1 kg) at 1.5% (PR) and 2% (F0 and F1) feeding rates respectively. There was no significant difference in P excretion between fish fed the F0 (5.5 g soluble P kg⁻¹ dry diet) and the PR diet. However, significantly higher (34.5%) amounts of non-faecal P excretions (7.4 g soluble P kg⁻¹ dry diet) were found in fish fed F1 compared with the F0 diet. This suggested that there was an excess of dietary P in the F1 diet and that supplementation is not needed in fish meal-based diets for large yellowtail.     

双热源半自动控温甜樱桃促成栽培系统设计与试验

为解决甜樱桃促成栽培产量和质量不稳定的问题,该研究根据甜樱桃促成栽培特点,研制了一种双热源半自动控温甜樱桃促成栽培系统。该系统以煤、柴为燃料的地炕式加热炉为补充加热方式,结合太阳能调控温度。通过与传统大棚比较,分析了该系统对甜樱桃栽培产量及经济效益的影响。结果表明:连续2 a应用甜樱桃促成栽培系统的大棚产量稳定在11 550 kg/hm2以上,优质果率超过80%,年经济效益比普通大棚高37%(2012年)和36%(2013年)。该系统采用半自动测控促成栽培环境,使环境因子的检测和报警实现自动化,明显降低了劳动强度,在甜樱桃促成栽培中推广应用,可取得显著经济效益。     

马铃薯的钾素需求及营养诊断

了解马铃薯的钾素营养特点是马铃薯养分管理的基础,综述了马铃薯钾素营养的研究进展,并提出了进一步研究的方向。尽管文献报道的马铃薯需钾量存在差异,但已有的研究结果表明,马铃薯是需钾量较大的作物,其对钾素的需求多于其他元素。而且与小麦等作物相比,马铃薯的钾素营养效率较低。已有的研究还证实土壤交换性钾含量与马铃薯产量的关系并不稳定,仅依靠土壤测试制定钾肥施用方案存在较大的误差,因而马铃薯钾素营养状况诊断并依此指导生育期钾肥施用就显得必要。业已发现叶柄钾浓度能很好的反映马铃薯植株的钾素营养状况,对土壤供钾高度敏感,与块茎产量存在很好的数量关系,因此,用于指导马铃薯施肥的叶柄的临界钾浓度被不同研究人员确立,但干重基础的叶柄钾浓度指标指导施肥实践的时效性较差,这意味着简便快速的诊断方法有待建立。     

冀京津冬小麦灌溉需水量时空变化特征

利用冀京津地区20个气象站点1961-2010年气象资料和1980-2009年冬小麦生育期资料,采用美国农业部土壤保持局推荐方法计算有效降水量,同时利用FAO推荐的Penman-Monteith方法计算冬小麦全生育期和4个主要生育阶段的需水量,并对冬小麦生育阶段灌溉需水量进行探讨。结果表明,过去50a来,冀京津冬小麦生育期内有效降水量呈增加趋势,空间上呈经向分布特点,表现为从西向东梯状增加的趋势。而冬小麦的需水量呈减少趋势,其中抽穗-乳熟期减少幅度最大,全生育期需水量的空间分布呈带状特征,全区差异较大。抽穗-乳熟期分布由东南向北递减。为满足冬小麦需水要求,全生育期灌溉需水量为291~381mm,灌溉需水量较多的地区为沧州市和衡水市一带。其中需水较多的生育阶段为拔节-抽穗期和抽穗-乳熟期。在空间上,拔节-抽穗期灌溉需水量以沧州市为中心,向南北两侧递减;抽穗-乳熟期灌溉需水量南高北低,有明显的带状分布特征。研究结果可为冀京津冬小麦适时定量灌溉和提高水分利用效率提供基础数据支撑。     

长期施肥对红壤磷组分及活性酸的影响

以12年的红壤长期肥力监测定位试验不同处理土壤为材料,研究了连续施肥对土壤磷组分、土壤对磷吸附解吸、土壤活性酸铝的影响。连续施用化学磷肥和化肥加有机肥,均可提高土壤全磷、无机磷数量。施用有机肥料,土壤中的磷以Ca-P和Al-P积累为主要表现形式,化学磷肥的施用能够提高土壤的全磷,并以Al-P增幅为最大,在所有处理中均表现为土壤O-P相对稳定。有机肥料处理土壤对外源磷的吸附强度明显少于施用化学磷肥和不施用磷肥的处理,有机肥料能够显著提高吸附磷的再利用,在NPKM处理中解吸磷占吸附磷的47.72%,M处理中占42.89%,其它处理中解吸磷占吸附磷数量一般少于8%。MNPK、M处理的PFI为2.51、2.69比N、NP处理4.53、4.37明显降低。在红壤旱地长期施用化学肥料,土壤交换性酸铝成倍增加,土壤酸化严重;施用有机肥料、有机肥料与化学肥料配合施用,土壤交换酸铝表现稳定。     

基于作物空间信息特征的灌区种植结构优化研究

针对目前北方许多大型灌区种植结构不合理、农业需水量偏大、水资源紧缺等问题,提出了一种基于作物空间信息特征的种植结构优化方法,通过调整种植结构和优化空间分布,减少农业需水量,提高农业效益。利用地统计学(GS)和地理信息系统(GIS)的空间处理能力,分区计算了灌区多年平均参考作物需水量(ET0)和作物需水量(ETc),并统计分区内作物单产和产值信息;构建了基于作物空间信息特征的多目标优化模型,设计了2种作物种植结构方案。结果表明,与传统多目标种植结构优化模型相比,基于作物空间信息特征的种植结构优化方法在节水效果和农业效益上都有一定的优势。     

河南省冬小麦年均需水量空间插值研究

解决冬小麦的需水信息通常采用水量的空间插值方法,而在众多空间插值方法中,没有绝对最优的空间插值方法,只有特定条件下的最优方法。对河南省的25个灌溉站点的冬小麦年均需水量数据,采用4种空间插值方法对各站点冬小麦年均需水量进行研究,综合分析得到,4种插值方法都能很好地反映25个站点的冬小麦年均需水量,无明显的系统误差,比较而言,整体多项式插值法最优。     

温室膜下滴灌条件下黄瓜需水规律研究

根据试验区温室黄瓜生育期环境因子实测资料,采用土壤水量平衡原理模拟了黄瓜生育期土壤含水量的变化过程,以模拟计算的土壤含水率与实际测试的土壤含水率的误差平方和最小为目标函数来确定温室膜下滴灌条件下的作物系数和作物需水量。结果表明,黄瓜生长期土壤含水率的模拟值和实测值较为吻合,两者相对误差在10%以内。作物系数在生长前期是逐渐变大,在作物生长旺盛时期作物系数达到最大值,随后逐渐减小,与作物叶面积指数的变化规律一致。温室黄瓜需水量在生长期的前期随时间的变化幅度较小,变化为1.5~3.5mm/d;中期随时间的变化幅度较大,变化为0.2~7.5mm/d;后期随时间的变化幅度又变小,变化为3.5~7.2mm/d。