长江流域土壤水量平衡与植被旱度研究

以流域为研究单元,采用水量平衡与估算法相结合的参考蒸散修正模型,定量分析了长江流域九个区域的不同水平年的土壤水分动态、植被耗水量、水分亏缺量及植被旱度。结果表明:长江中下游流域植被旱度较大,特别是偏枯年。不同区域四季干旱规律、干旱程度不同,各有特点。长江流域的水量平衡中水分蒸散是主要的输出形式。因蒸散力较大,所以植被旱度较大,植被恢复要充分考虑其水分条件,选择合适条件的物种。     

辽西风沙半干旱区旱作农田水资源研究

辽西风沙半干旱区年降水量多为二、三年左右的丰枯交替,并有持续4年以上的连续干旱,尤其是1980年以后连续干旱的年份较多。区域内春旱严重,夏季降水明显集中,秋季水分收支基本平衡。以土壤水分季节变化情况可分为:冬季土壤水分凝聚、冻结、累积阶段,春季解冻、返浆、土壤水分大量蒸散阶段,夏季土壤水分大量累积阶段,秋季土壤水分缓慢蒸发阶段。     

华南典型人工林的土壤物理性质及其水源涵养功能

对杉木、马尾松、湿地松、尾叶桉和马占相思林的土壤物理性质、凋落物持水量以及土壤贮水性能进行了研究。5种林分土壤的毛管孔隙度、非毛管孔隙度和总孔隙度均为上层大于下层,而土壤容重为上层小于下层。总体来看,5种林分中杉木和马占相思林土壤疏松、孔隙度大;尾叶桉林土壤紧实、孔隙度小,马尾松林和湿地松的土壤孔隙度中等。凋落物最大持水量呈现杉木林(18thm-2)>马占相思林(15thm-2)>尾叶桉林(14thm-2)>马尾松林(11thm-2)>湿地松林(10thm-2)。土壤是森林涵养水源的主体,其最大持水量占林地最大持水量的99%以上,顺序为杉木林地和马占相思林(2064和2061thm-2)>湿地松林(2041thm-2)>马尾松林(2032thm-2)>尾叶桉林(1941thm-2)。林地最大持水量的顺序为杉木林地(2082thm-2)>马占相思林地(2076thm-2)>湿地松林地(2051thm-2)>马尾松林地(2043thm-2)>尾叶桉林地(1955thm-2)。     

Total and available tryptophan requirement of Nile tilapia,Oreochromis niloticus,fingerlings

The dietary total and available requirement of tryptophan of Nile tilapia fingerlings was determined using linear regression analysis. Six hundred fish (3.4 ± 0.0 g) were fed diets containing 296.4 g/kg of crude protein and 14.1 MJ/kg of digestible energy. Five extruded diets containing 2.5, 3.0, 3.4, 3.8 and 4.2 g/kg of total tryptophan were evaluated. Fish were fed four times a day during 45 days. Final body weight, weight gain, feed intake, feed conversion ratio and net protein utilization of fish fed Trp 3.4 and Trp 3.8 diets were improved compared to fish fed Trp 2.5 and Trp 4.2 diets. No significant differences in survival rate, whole‐body moisture and ash were observed. Whole‐body amino acid profile of fish fed different diets did not differ statistically (p > .05). Fish fed Trp 3.0 and Trp 3.4 diets showed higher tryptophan retention compared to fish fed Trp 2.5 and Trp 4.2 diets. Excepting blood glucose, no effects of dietary tryptophan on haematological parameters were observed. The dietary total tryptophan requirement of Nile tilapia fingerlings based on weight gain was estimated to be 3.4 g/kg (11.0 g/kg of dietary crude protein) or 3.0 g/kg of available tryptophan (11.0 g/kg of dietary digestible protein).     

保水剂与秸秆深施对砂质潮土水肥状况及小麦产量的影响

保水剂与秸秆深施对砂质潮土培肥效应的研究,为中低产田砂质潮土的改良提供科学合理的依据。于典型的砂质潮土区设置了五种不同的田间处理方式:秸秆翻埋还田(TS)、秸秆深施(DS)、秸秆与保水剂深施(DS+W)、保水剂深施(DW)和不处理对照(CK)。比较分析了小麦生育期不同土层中水分、有机质、速效氮以及小麦产量。研究结果表明:(1)与CK相比,从孕穗期到灌浆期,秸秆与保水剂的施用均使0~80 cm土层的含水量有所提高,且DS+W与DW均显著提高了60~80 cm土层水分,其中在孕穗期两处理水分含量分别是CK的3倍和2倍,灌浆期为CK的2倍和1.5倍。(2)与CK相比,其余各处理均显著提高了小麦产量(P<0.05),TS、DS和DS+W分别增产了30.7%、27.3%和48.9%。(3)与CK相比,TS、DS、DS+W和DW的水分利用效率显著增加,分别增加了0.63、0.57 0.93和0.29 kg m~(-3)。(4)与CK相比,20~80 cm土层中,深埋处理DS、DS+W、DW均提高了土壤中有机质含量,DS+W处理下土壤有机质含量与其他处理之间差异显著(P<0.05)。(5)与CK相比,TS和DS处理能够有效的提高各土层中硝态氮含量,保水剂的施用在40~80 cm土层中对土壤硝态氮未见显著影响。(6)各处理间单茎小麦各器官干物质积累量大小为:DS+W>DS>TS>DW>CK,且从不同器官的干物质积累量的比例来看,TS、DS、DS+W处理下的籽粒所占比重较CK的籽粒所占比重有所增加,茎+叶所占比例相应减少,植株干物质的积累逐渐向籽粒偏斜。(7)从小麦产量与土壤水分和硝态氮含量的相关分析结果来看,土壤水分主要在小麦灌浆期影响小麦产量,且是砂质潮土中影响小麦产量的最主要因素。综上所述,保水剂与秸秆的施用均能不同程度的改善砂质潮土的理化性状,提高农作物产量,以保水剂与秸秆的配合深施对砂质潮土的改良效果最佳。     

日光温室土壤养分含量及比例与种植年限的关系

对陕西省泾阳县的日光温室蔬菜施肥情况与土壤养分状况进行了研究。结果表明,泾阳县日光温室氮磷钾养分的纯投入量平均为N·651 kg hm~(-2)、P2O5·485 kg hm~(-2)和K2O·855 kg hm~(-2),养分投入量明显偏高。温室耕层土壤速效磷、速效钾、水溶性钾和水溶性钙与种植年限之间都存在极显著的线性正相关关系,相关系数分别为0.995、0.973、0.973和0.979。种植7年后,硝态氮、速效磷、速效钾的含量分别是农田土壤的1.8、5.1和3.6倍,水溶性钾、钙、镁分别是农田的12.2、4.5和2.6倍。随种植年限的延长,温室土壤K、Ca、Mg三者的比例严重失衡,由养分不合理施用带来的养分损失及可能引起的环境问题值得关注。     

生物炭和无机肥对盐碱滩涂围垦农田土壤性状的影响

在重度盐碱滩涂围垦的土地上,添加不同量的生物炭(0、3、6、9 hm~(-2)),在玉米不同生育期施加无机肥,对照CK不施肥,研究土壤在不进行作物种植下的性状变化。结果表明:自然条件下重度盐碱土地土壤物理性状变差,施用无机肥加剧了土壤的退化程度;在未种植作物条件下,生物炭添加没有对降低土壤容重起到促进作用,同时也没有提高土壤饱和含水量及田间持水量;团聚体组成分析显示生物炭用量在3 t hm~(-2)时土壤中2 mm团聚体增加最多;雨季时雨水淋洗显著降低土壤0~20 cm土层盐分,生物炭用量越大土壤盐分淋洗效果越明显;八月份和九月份时随着雨季结束,地下水位升高、太阳辐射增强加速了盐分在表层土壤的积聚,生物炭添加能有效抑制盐分在表层的积累,但无机肥添加又阻碍了这种抑制作用。     

沟垄二元覆盖对渭北旱塬区土壤肥力及玉米产量的影响

探讨沟垄二元覆盖对旱地土壤肥力及作物生产力的影响,对完善半湿润区作物微集水栽培技术具有重要的理论和实践意义。2007—2011年在渭北旱塬进行5年定位试验,设置垄上覆地膜,沟内分别覆普通地膜、生物降解膜、玉米秸秆、液体地膜和沟不覆盖等不同沟垄覆盖模式,以传统平作为对照。结果表明,2011年春玉米收获后各处理土壤有机质及速效养分含量随土层的加深而降低,与2007年试验处理前相比,沟垄二元覆盖各处理土壤养分含量明显增加,而垄覆地膜+沟不覆盖和传统平作处理有所下降。垄覆地膜沟覆秸秆处理0~20 cm层土壤有机质、碱解氮、有效磷和速效钾含量均显著高于对照,垄覆地膜沟覆地膜和垄覆地膜沟覆生物降解膜处理有机质和碱解氮含量较对照有所增加,而其有效磷和速效钾含量显著增加。20~60 cm层土壤有机质和速效养分含量各沟垄二元覆盖处理均略高于对照。各沟垄覆盖处理表层(0~20 cm)土壤脲酶、磷酸酶和蔗糖酶活性均较对照增加,且以垄覆地膜沟覆秸秆处理土壤酶活性最高,垄覆地膜沟覆生物降解膜和垄覆地膜沟覆地膜处理次之。垄覆地膜沟覆生物降解膜、垄覆地膜沟覆地膜和垄覆地膜沟覆秸秆处理较对照显著增产41.1%、42.1%、39.3%,水分利用效率显著提高38.0%、39.6%、37.0%。在渭北旱塬区进行沟垄二元覆盖对提高土壤肥力、酶活性及春玉米产量和水分利用效率有显著提高作用,以垄覆地膜沟覆秸秆处理最佳,垄覆地膜沟覆地膜和垄覆地膜沟覆生物降解膜次之。可见,垄覆地膜沟覆地膜、生物降解膜或秸秆的沟垄全覆盖种植在渭北旱塬雨养农业区春玉米生产栽培具有一定的可行性和应用价值。     

Greenhouse gas emissions in response to straw incorporation,water management and their interaction in a paddy field in subtropical central China

A field experiment was conducted to study the effects of combination of straw incorporation and water management on fluxes of CH₄, N₂O and soil heterotrophic respiration (Rh) in a paddy field in subtropical central China by using a static opaque chamber/gas chromatography method. Four treatments were set up: two rice straw incorporation rates at 0 (S1) and 6 (S2) t ha^?1 combined with two water managements of intermittent irrigation (W1, with mid-season drainage) and continuous flooding (W2, without mid-season drainage). The cumulative seasonal CH₄ emissions for the treatments of S1W2, S2W1 and S2W2 increased significantly by 1.84, 5.47 and 6.63 times, respectively, while seasonal N₂O emissions decreased by 0.67, 0.29 and 1.21 times, respectively, as compared to S1W1 treatment. The significant increase in the cumulative Rh for the treatments S1W1, S2W1 and S2W2 were 0.54, 1.35 and 0.52 times, respectively, in comparison with S1W2. On a seasonal basis, both the CO₂-equivalents (CO₂e) and yield-scaled CO₂e (GHGI) of CH₄ and N₂O emissions increased with straw incorporation and continuous flooding, following the order: S2W2>S2W1>S1W2>S1W1. Thus, the practices of in season straw incorporation should be discouraged, while mid-season drainage is recommended in paddy rice production from a point view of reducing greenhouse gas emissions.