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。     

Effect of dietary supplemental l‐carnitine on growth performance,body composition and antioxidant status in juvenile black sea bream,Sparus macrocephalus

Effects of dietary l ‐carnitine were studied in juvenile black sea bream (Sparus macrocephalus). The semipurified basal diet [crude protein 450 g kg^?1 dry matter (DM); crude lipid 126 g kg^?1 DM] was formulated to choose white fishmeal as the protein source and fish oil plus corn oil (1 : 1) as the lipid source. Six diets (control + diets 1–5) containing 0.1, 0.12, 0.16, 0.24, 0.39 and 1.1 g of l ‐carnitine kg^?1 diet were fed to triplicate groups of black sea bream (initial weight 13.10 ± 0.05 g) for 8 weeks. At the end of the feeding trial, growth performance, body composition and antioxidant status were determined. The results showed that relative growth rate (RGR) was significantly improved by the elevation of dietary l ‐carnitine level from 0.1 to 0.24 g kg^?1, but decreased with further increment (P < 0.05). Lipid content decreased significantly (P < 0.05) in the dorsal muscle whereas increased (P < 0.05) in the liver with the addition of dietary l ‐carnitine. Dietary l ‐carnitine supplements elevated enzymatic antioxidants (superoxide dismutase, SOD; catalase, CAT; glutathione‐S‐transferase, GST) activities (P < 0.05) yet decreased the content of non‐enzymatic factor, total sulphydryl groups (TSH) (P < 0.05). In summary, the optimum dietary l ‐carnitine level was 0.284 g kg^?1 diet by second‐polynomial regression analysis based on RGR (y = ?647.4x² +367.97x + 234.55; R² = 0.977, x = dietary l ‐carnitine levels, y = RGR), and dietary l ‐carnitine addition within the levels adopted in our study could depress lipid peroxidation in tissues of juvenile black sea bream.     

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.     

The roles of light and pericarp on seed dormancy and germination in feral Raphanus sativus (Brassicaceae)

The timing of seed germination may determine the success of a weed species in an agroecosystem, and its expression is modulated by environmental conditions, but also by seed physiology and anatomy. The aims of this study were to investigate the roles of light, pericarp, dry storage and cold stratification on seed dormancy and germination in feral radish, a troublesome agricultural weed in temperate zones of the Americas that reduces crop yields. To this end, we used isolated intact pods and extracted seeds to test germination over time under contrasting temperature, light and storage conditions. Here, we showed that fresh seeds were non‐dormant, but that light and the presence of the pericarp reduced germination, especially under low temperatures. The pericarp reduced the final water content absorbed by seeds inside pods and decreased absorption/dehydration rates. The pericarp showed several small lignified cell layers in the endocarp, and x‐ray images displayed the lack of space between the partially embedded seed and the endocarp. Dry storage and cold stratification were ineffective in breaking the dormancy imposed by the pericarp. The apparent requirement for darkness and the mechanical restriction of the pericarp may have the potential to induce dormancy, spreading the timing of seed germination over a more extended period and hindering the control of feral radish.     

不同水分处理条件下小麦需水规律研究

对小麦需水量与产量的关系进行了试验研究。结果表明,小麦需水量与产量关系呈二次抛物线关系,函数式y=-0.434 1 x2+348.66 x-67 248。在整个生育期中,小麦苗期需水强度最低,拔节期至成熟期小麦的需水强度基本随着生育期的推进逐渐上升并在孕穗至成熟期达到峰值,说明拔节期~孕穗期为小麦的生长旺盛期。试验成果为制定贵州小麦灌溉制度提供了参考依据。     

辽河河口湿地生态环境需水量研究

科学合理地确定辽河河口湿地的适宜与最小生态环境需水量是维持其生态系统健康的重要保障。利用3S技术提取辽河河口湿地覆被信息,将生态环境需水量的计算类型划分为消耗型和非消耗型,建立了适合辽河河口湿地的计算模型,并利用该模型计算了研究区2000、2005和2014年的生态环境需水量以及适宜生态环境需水量与不同降水频率条件下的最小生态环境需水量。结果表明,研究区适宜生态环境需水量为99 554.92×10~4m~3;多年平均降水条件下、75%降水频率下和95%降水频率下对应的最小生态环境需水量分别为20 220.13×10~4m~3、22 362.31×10~4m~3和24 314.98×10~4m~3。     

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。     

水稻不同需水关键期适宜灌水下限指标研究

在5 m2有底测坑内研究水稻拔节孕穗期和抽穗开花期70%～90%土壤饱和含水率灌水下限对灌溉制度、渗漏量和产量等的影响。结果表明,不同灌水条件下,灌水次数、灌水模数、灌溉定额发生较大变化,灌水次数在本田期为28～37次,灌溉定额为8 190～9 450 m3/hm2,各处理渗漏量随着灌水量的降低而降低,渗漏量为灌水量的54.22%～64.25%,拔节孕穗期较抽穗开花期需水更敏感,拔节孕穗期应保持湿润状态,抽穗开花期适宜灌水下限为90%。     

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。     

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。