施氮对关中还田玉米秸秆腐解和养分释放特征的影响

在陕西关中平原的冬小麦-夏玉米轮作区,采用尼龙网袋田间填埋与¹⁵N同位素标记玉米秸秆相结合的方法,设置不施氮和施氮200 kg·hm^-2两个处理,研究施氮对小麦生长期内还田玉米秸秆腐解的影响以及腐解过程中秸秆碳、氮、磷、钾的养分释放.结果表明: 从小麦播种到越冬期,施用氮肥对秸秆碳和干物质分解无显著影响,但可促进秸秆中磷的释放,抑制氮和钾的释放.灌浆到成熟期,氮肥对秸秆腐解及其N、P、K养分的释放无显著影响,但秸秆碳的释放显著增加.不同生育期,玉米秸秆碳的释放与干物质分解变化趋势一致,C/N逐渐下降.种植一季小麦后,秸秆干物质累计腐解率不足50%;秸秆碳释放率为47.9%～51.1%,不施氮和施氮处理的秸秆C/N分别由32.2降低到20.2和17.9.小麦收获时,秸秆氮、磷、钾均为净释放,氮释放量为7.2～9.4 kg·hm^-2,占秸秆氮的12.7%～16.6%;磷释放量为1.29～1.44 kg·hm^-2,占29.0%～32.4%;钾的释放量大、释放快,越冬前超过80%,成熟时释放量为51.8～52.5 kg·hm^-2,占90.5%～91.7%.在秸秆还田条件下,应考虑秸秆归还的钾,减少小麦钾肥用量,适量补充氮、磷.     

施氮和秸秆还田对晚播小麦养分平衡和产量的影响

在大田条件下,研究了水稻秸秆还田和施氮量对晚播小麦产量、养分积累、秸秆养分释放及养分平衡的影响.结果表明: 水稻秸秆还田并配施适当的施氮量有利于提高晚播小麦籽粒产量.晚播小麦全生育期的干物质、氮、磷、钾积累量均随施氮量增加而显著增加,相同施氮量(270 kg N·hm^-2)下,秸秆还田处理的干物质、磷、钾积累高于不还田处理,氮积累则呈相反趋势.随着施氮量增加,秸秆腐解和养分释放率增加,且拔节后秸秆养分释放量占总释放量的比例降低;随生育进程的推进,秸秆的干物质、磷、钾释放量呈倒“N”型变化趋势,而氮释放量则呈“V”型变化趋势.计算养分表观平衡结果表明,秸秆还田并增加施氮量,养分总盈余量显著升高;在获得较高产量的施氮条件下,氮、钾素显著盈余,磷素投入较为合理.晚播小麦实行秸秆还田后,可适当增加氮肥用量至257 kg·hm^-2,并减少钾肥投入.     

秸秆还田配施不同比例化肥对晚稻产量及土壤养分的影响

在不同秸秆还田方式对早稻的效应研究确定的最佳还田方式和还田量(粉碎还田3000 kg/hm2)基础上,以单施秸秆为对照,研究了秸秆还田配施不同比例化肥对晚稻产量、干物质积累与分配及土壤养分的影响。结果表明:(1)与对照相比,秸秆3000 kg/hm2+N 150 kg/hm2+P2O575 kg/hm2+K2O 37.5 kg/hm2增产效果最为显著,在水稻的每穗粒数、千粒重、结实率、充实度和产量等方面增加幅度最大,分别为9.32%、4.28%、13.70%、2.74%和26.38%。(2)各处理的干物质茎鞘比例随着生育进程不断降低,从孕穗期的66.68%—77.00%降低至成熟期的25.97%—34.79%,除SNPK1外,叶片比例从孕穗期的23.00%—33.32%降低至成熟期的7.41%—21.03%;秸秆还田配施不同比例化肥处理的茎鞘比例在孕穗期、抽穗期和成熟期高于对照,而叶片比例与茎鞘比例呈相反趋势。(3)与对照相比,秸秆还田配施不同比例化肥处理提高了土壤pH值、有机碳、全氮、碱解氮、全磷、有效磷、全钾、速效钾,降低了土壤C/N比。研究结果说明,秸秆还田配施不同比例化肥可以提高植株干物质积累速率、群体生物量,合理改善土壤养分,保证较高的水稻增产潜力,其中秸秆3000 kg/hm2+N 150 kg/hm2+P2O575 kg/hm2+K2O 37.5 kg/hm2效果最为显著。     

秸秆还田对水稻固碳特性及产量形成的影响

以中浙优1号为材料、秸秆不还田为对照,在大田试验条件下研究了不同秸秆还田量（4000、6000、8000 kg·hm^-2）对水稻群体干物质积累、运转、植株固碳及产量形成的影响. 结果表明： 与对照相比,秸秆还田处理的水稻群体干物质积累总量平均增加63.03 g·m^-2,以6000 kg·hm^-2处理的干物质积累量最高,比对照增加154.40 g·m^-2;在水稻各生育阶段中,秸秆还田处理对分蘖盛期—齐穗期干物质积累的影响最为明显,干物质积累量比对照平均增加71.25 g·m^-2;与对照相比,秸秆还田处理的茎叶干物质输出率和表观转变率分别平均增加4.2%和3.7%,均以6000 kg·hm^-2处理最高,分别为12.8%和11.1%.秸秆还田处理的群体植株固碳量比对照平均增加55.38 g·m^-2,以6000 kg·hm^-2处理的增幅最大,为17.8%;从固碳量在各器官中的分配来看,秸秆还田有利于生育前期茎叶固碳量的积累和生育后期固碳量向穗部的分配.秸秆还田处理的水稻产量比对照平均增加794.59 kg·hm^-2,增幅9.5%,其中6000和4000 kg·hm^-2处理的产量均显著提高,而8000 kg·hm^-2处理的产量增加不显著;从产量构成因素来看,秸秆还田处理单位面积有效穗数的增加是增产的主要原因,平均增加8.4穗·m^-2.     

The effect of prolonged storage on the digestibility and nitrogen content of ammonia-treated barley straw

Barley straw in a 10-t stack was treated with anhydrous ammonia (40 kg t^?1 straw dry matter). Four bales, two buried in the stack and two with one face exposed, were sampled before treatment, at 54 days (1 day after the stack was first opened) and at regular intervals thereafter for a further 12 days. The total nitrogen content of the straw increased from the 6.7 g kg^?1 straw dry matter present before treatment to 20.7 g kg^?1 at day 54. Ammonia nitrogen contributed 7.4 g and non-ammonia nitrogen 6.6 g of this increase. There was a rapid loss of ammonia on opening the stack and this continued for the first week; thereafter ammonia was lost at a much slower rate. In all, 39% of the ammonia nitrogen present 1 day after opening was lost by the end of the sampling period. This loss accounted for the 18% reduction in total nitrogen recorded over the same period. Loss of nitrogen did not affect the digestibility of treated straw as determined by the nylon bag method using sheep. Digestibility, whether expressed as loss of dry matter or as digestibility of cellulose, remained constant throughout. Added water-insoluble nitrogen appeared to be more readily available than that initially present in untreated straw. The position of bales within the stack did not affect results significantly.     

Water and Nitrogen Uptake in Upland and Swamp Rice

The water uptake per unit dry matter and nitrogen uptake perunit water absorbed of swamp rice (Dima) and upland rice (Kindinga)at three nitrogen levels equivalent to 23.6, 70.8, and 118,kg./ha. (20, 60 and 100 lb./acre) respectively were studiedunder tropical green-house conditions in Trinidad. The water uptake per unit dry matter produced was significantlygreater in Kindinga than in Dima at the three nitrogen levels.Additional nitrogen increased the water requirement of Kindingabut decreased that of Dima, the greater increase in Kindingabeing attributed to increase in leaf area. The efficiency of nitrogen absorption in terms of water transpiredwas greater in Dima than in Kindinga at the three nitrogen levels.     

秸秆和氮肥不同配比影响平邑甜茶幼苗的生长和对氮素的吸收、分配和利用

为探讨秸秆和氮肥不同配比对平邑甜茶(Malus hupehensis)植株生长和氮素吸收、分配和利用的影响, 采用¹⁵N同位素示踪技术, 以二年生盆栽平邑甜茶为试材, 研究了不同秸秆和氮肥配比条件下平邑甜茶的生长、¹⁵N尿素吸收利用和土壤碳氮比等参数, 发现秸秆和氮肥不同配比对平邑甜茶植株的生长及¹⁵N-尿素的吸收、分配和利用具有不同的影响。园土和秸秆比在45:1的水平, 同时配施氮肥(N 300 mg·kg^-1)时, 植株株高、茎粗和植株总干重的值最高, 分别为85.33 cm、8.05 mm和74.68 g; 植株的全氮、¹⁵N吸收量和利用率也最大, 分别为0.938 g、0.029 g和9.74%。不加秸秆而仅施加氮肥(N 200 mg·kg^-1)的对照(CK)的根冠比最大, 为1.54, 显著高于其他各种处理。各试验处理地上部分从肥料中吸收分配到的¹⁵N量对地上部分全氮量的贡献率(Ndff)均大于地下部分, 且CK各器官Ndff值最高, 地上部分和地下部分分别为7.94%和4.69%。除CK外, 各处理¹⁵N分配率均是地上部>地下部。秸秆的施用显著提高了土壤的有机质、全氮含量和土壤有机质C/N比。相关性分析结果表明, 土壤有机质C/N比与植株地下部分Ndff值有极显著负相关性(p < 0.01), 与植株整株Ndff值有显著负相关性(p < 0.05)。建议果园秸秆配施氮肥时, 控制秸秆施用量在45:1水平, 氮肥在200-300 mg·kg^-1之间较好。     

耕作方式对潮土土壤团聚体微生物群落结构的影响

为探究不同耕作方式对潮土土壤团聚体微生物群落结构和多样性的影响,采用磷脂脂肪酸(PLFA)法测定了土壤团聚体中微生物群落。试验设置4个耕作处理,分别为旋耕+秸秆还田(RT)、深耕+秸秆还田(DP)、深松+秸秆还田(SS)和免耕+秸秆还田(NT)。结果表明:与RT相比,DP处理显著提高了原状土壤和>5 mm粒级土壤团聚体中真菌PLFAs量和真菌/细菌,为真菌的繁殖提供了有利条件,有助于土壤有机质的贮存,提高了土壤生态系统的缓冲能力;提高了5～2 mm粒级土壤团聚体中细菌PLFAs量,降低了土壤革兰氏阳性菌/革兰氏阴性菌,改善了土壤营养状况;提高了<0.25 mm粒级土壤团聚体中微生物丰富度指数。总的来说,深耕+秸秆还田(DP)对土壤团聚体细菌和真菌生物量有一定的提高作用,并且在一定程度上改善了土壤团聚体微生物群落结构,有利于增加土壤固碳能力和保持土壤微生物多样性。冗余分析结果表明,土壤团聚体总PLFAs量、细菌、革兰氏阴性菌和放线菌PLFAs量与土壤有机碳相关性较强,革兰氏阳性菌PLFAs量与总氮相关性较强。各处理较大粒级土壤团聚体微生物群落主要受碳氮比、含水量、pH值和团聚体质量分数的影响,较小粒级土壤团聚体微生物群落则主要受土壤有机碳和总氮的影响。     

Seasonal distribution and changes in the nutritive quality of living,dead and detrital fractions of Zostera marina L.

Samples of eelgrass, Zostera marina L., were collected monthly from December 1974 through December 1975 in a shallow embayment near Beaufort, N.C., and separated into green leaves, dead leaves, and leaf detrital material. Each component was analysed for dry weight, organic matter, inorganic and organic carbon, nitrogen and amino compounds.The standing crop of green and dead blades reached a maximum in April through June, while detrital matter had peaks in December, April and July–September. Inorganic carbon in the three grass fractions showed seasonal variations similar to those observed for epiphytic biomass in previous years, and represented 14, 24, and 30% of the total carbon associated with the green and dead leaves and detrital fragments, respectively. Organic carbon represented a decreasing proportion of the dry weight of these three fractions on a dry weight basis while there was a significant increase in organic carbon on an ash-free dry weight basis in the detrital fragments relative to the head dead blades. During senescence there was a loss of nitrogen from the leaves and an increase in the nitrogen content of the organic matter of the detritus relative to the dead leaves. The latter suggests that there was microbial growth on the detritus and subsequent nitrogen immobilization from the surrounding medium. There were significant decreases of lysine, histidine, arginine, glycine, tyrosine, and glucosamine in the dead leaves relative to the detritus. The glucosamine, derived from N-acetyl-glucosamine, a product of murein which is a component of microbial cell walls, had a seasonal distribution similar to that of the epiphytic community and available inorganic nitrogen in the surrounding water. The relative proportions of N-acetyl-glucosamine, nitrogen and organic carbon were all higher in the fall and winter.     

Depth-related variation in gross chemical composition of several seaweeds

The percentages of dry weigth, ash, carbon and nitrogen in Chondrus crispus Stackh. and Furcellaria lumbricalis (Huds.) Lamour. were determined for plants distributed along a depth gradient. Analyses were made of samples collected from June throug August. Dry weights and ash were also determined for other major perennial species, but on fewer samples. In all instances the trend was an increase in ash as a percentage of the dry weight and a decrease in the percentage dry weight and organic matter, with depth. The percentage of carbon also decreased with depth, reflecting the changes in organic matter. However, the percentage of nitrogen increased with depth, thus the C/N ratio decreased with depth. These changes in gross chemical composition are assumed to be analogous to seasonal changes in composition at a given depth or level in the littoral zone.     

Composting of poultry manure and wheat straw in a closed reactor: optimum mixture ratio and evolution of parameters

The main objectives of this work were to investigate the evolution of some principal physico-chemical properties (temperature, carbon dioxide, oxygen, ammonia, pH, electrical conductivity, organic matter) and microbial population (mesophilic and thermophilic bacteria and fungi) during composting poultry manure with wheat straw in a reactor system, and to evaluate the optimum mixture ratio for organic substrate production. The experiments were carried out in four small laboratory reactors (1 l) and one large reactor (32 l) under adiabatic conditions over 14 days. During the process the highest temperature was 64.6°C, pH varied between 7.40 and 8.85, electrical conductivity varied between 3.50 and 4.31 dS m⁻¹ and the highest value of organic matter (dry weight) degradation was 47.6%. Mesophilic bacteria and fungi predominated in the beginning, and started the degradation with generation of metabolic heat. By increasing the temperature in reactors, the number of thermophilic microorganisms also increased, which resulted in faster degradation of substrate. The application of a closed reactor showed a rapid degradation of manure/straw mixture as well as a good control of the emissions of air polluting gases into atmosphere. The results showed that the ratio of manure to straw 5.25:1 (dry weight) was better for composting process than the other mixture ratios.     

Influence of wheat cultivars on straw quality and Pleurotus ostreatus cultivation

The main raw material for Pleurotus ostreatus (oyster mushroom) cultivation is wheat straw. Estimation of straw biodegradability from 15 different spring wheat cultivars under irrigation in South Africa was determined using linear discriminant analysis to discriminate or group the 15 cultivars by combining chemical analysis and in vitro enzymatic hydrolysis. Significant differences (P < 0.01) were found between ash, nitrogen, reducing sugars, anthrone reactive-carbohydrates, water-soluble dry matter, and oyster mushroom yields. The significance of these measurements was investigated and discussed.     

The intake of steers and heifers fed on mixtures of alkali-treated or untreated straw with grass silage

Two experiments were made to investigate the intake of cattle when offered straw and silage mixtures.In a trial of changeover design 12 Friesian castrates (steers) were offered five diets. These were grass silage alone or mixed with untreated or NaOH treated straw supplying 20 or 40% of the total dry matter. The addition of 20% straw to the diet significantly reduced dry matter intake, and a further reduction occurred at 40%. Treating the straw with NaOh did not increase dry matter intake but led to an associated increase in digestible organic matter intake.Twelve Ayrshire heifers were given four diets in a trial of changeover design. The diets were silage only and three straw : silage mixtures in which straw provided 40% of the dry matter. The straws were untreated, NaOH treated or KOH treated. Untreated straw markedly depressed dry matter intake; NaOH raised the digestibility of straw and thus increased digestible organic matter intake significantly. The dry matter intake of the heifers was much greater than anticipated with the KOH treated straw : silage mixture and was similar to that achieved with silage only.     

间作绿肥对油菜根际土壤碳氮及根际微生物的影响

在我国西南紫色土地区,农田生态环境极为脆弱,绿肥应用也面临严峻问题。为改善农田土壤健康状况,探索绿肥的应用途径,通过紫云英与油菜间作,重点探讨了绿肥紫云英对油菜根际土壤碳氮及其微生物特征的影响,同时与秸秆覆盖的效应作了比较,其创新性在于将绿肥紫云英应用于西南旱地,并且为建立新的油菜种植模式作铺垫。结果表明:与秸秆覆盖相比,间作绿肥紫云英是影响油菜根际土壤环境的主要因素。间作紫云英减少了油菜根际土壤碳、氮含量,改变了油菜根际土壤碳氮比。间作紫云英也减少了油菜根际土壤微生物量,改变了油菜根际土壤微生物群落结构,改善了油菜根际土壤通气状况,抑制了厌氧细菌的生长。     

Immobilization,mineralization and the availability of the fertilizer nitrogen during the decomposition of the organic matters applied to the soil

Summary Immobilization and mineralization of the tracer nitrogen (K¹⁵NO₃) applied to the soil together with several organic matters during their decomposition was investigated in incubation experiments.After incubation for three months at 30°C, the decomposition rates of rice straw, hardwood bark, sawdust, softwood bark and peat moss were 41, 15, 7, 5, and 5%, respectively. After incubation for three months at 30°C, 100 and 80% of the fertilizer nitrogen were immobilized in the treatment with 2.0% of rice straw and sawdust carbon, respectively. These resulted in the lowered uptake of the fertilizer nitrogen by plants. In case of peat moss and barks, the amount of fertilizer nitrogen which transformed to the organic nitrogen fractions was quite small and the plant uptake of the nitrogen was hardly affected. Remineralization of the immobilized nitrogen was clearly observed after 2 months' incubation in case where rice straw carbon was added to the extent of 0.5 and 1.0%, but it was not observed in case where other organic matter carbon was added.The data showed that peat moss and barks were highly resistant to the action of microorganisms. As a results the immobilization process of the fertilizer nitrogen incubated with these organic matter was quite slow.     

The enzymatic hydrolysis and fermentation of pretreated wheat straw to ethanol

Autohydrolysis and ethanol-alkali pulping were used as pretreatment methods of wheat straw for its subsequent saccharification by Trichoderma reesei cellulase. The basic hydrolysis parameters, i.e., reaction time, pH, temperature, and enzyme and substrate concentration, were optimized to maximize sugar yields from ethanol-alkali modified straw. Thus, a 93% conversion of 2.5% straw material to sugar syrup containing 73% glucose was reached in 48 h using 40 filter paper units/g hydrolyzed substrate. The pretreated wheat straw was then fermented to ethanol at 43 degrees C in the simultaneous saccharification and fermentation (SSF) process using T. reesei cellulase and Kluyveromyces fragilis cells. From 10% (w/v) of chemically treated straw (dry matter), 2.4% (w/v) ethanol was obtained after 48 h. When the T. reesei cellulase system was supplemented with beta-glucosidase from Aspergillus niger, the ethanol yield in the SSF process increased to 3% (w/v) and the reaction time was shortened to 24 h.     

秸秆、有机肥及氮肥配合使用对水稻土微生物和有机质含量的影响

通过大田试验,研究了秸秆还田、施用有机肥和氮肥对水稻土微生物和土壤有机质含量的影响。试验结果表明:(1)在秸秆还田的情况下,增施氮肥(0-330kg/hm2范围内)可促进秸秆的的腐解;(2)秸秆还田、施用有机肥和氮肥中的单一措施均能不同程度地增加水稻土壤细菌、真菌、放线菌的数量;(3)综合运用秸秆还田、施用有机肥和氮肥措施能协同增加土壤微生物数量,提高土壤生物量态氮和有机质含量,以秸秆还田量为6000kg/hm2、施用有机肥量为4500kg/hm2、施用氮肥量为240kg/hm2效果较佳。     

毛壳霉CQ31的鉴定及固体发酵产木聚糖酶条件的优化

从土壤中筛选出一株产木聚糖酶的真菌CQ31, 经鉴定后命名为毛壳霉CQ31。该菌能够利用几种农业废弃物固体发酵高产木聚糖酶, 玉米杆为最佳碳源。单因素优化试验表明: 以玉米杆为碳源, 胰蛋白胨为氮源, 初始水分含量80%, 初始pH值9.0为最佳产酶条件。在优化后的条件下培养7 d产木聚糖酶水平高达4897 U/g干基碳源, 此时甘露聚糖酶酶活达803 U/g干基碳源。因此, 毛壳霉CQ31固体发酵产木聚糖酶和甘露聚糖酶具有一定的工业化应用前景。     

樟绒枝霉(Malbranchea cinnamomea)固体发酵产木聚糖酶的发酵条件优化

[目的] 研究樟绒枝霉(Malbranchea cinnamomea) CAU521利用农业废弃物固体发酵产木聚糖酶的发酵条件.[方法]采用单因素试验法优化影响菌株产酶的各个条件,包括碳源种类、氮源种类、初始pH、初始水分含量、培养温度及发酵时间共6个因素.[结果]获得的最佳产酶条件为:稻草为发酵碳源、2％(W/W)的酵母提取物为氮源、初始pH 7.0、初始水分含量80％和发酵温度45℃.在此条件下发酵6d后木聚糖酶的酶活力达到13 120 U/g干基碳源.[结论]樟绒枝霉固体发酵产木聚糖酶的产酶水平高,生产成本低,具有潜在的工业化应用前景.     

有机物添加下太岳山油松林土壤微生物元素组成的稳态分析

在山西太岳山地区,向油松林土壤中分别添加生物炭、玉米秸秆、蒙古栎叶、油松叶、木屑等5种有机物,测定各处理的土壤养分、酶及微生物生物量等指标,研究外源有机物添加下土壤酶化学计量特征及微生物元素组成的内稳性。结果表明: 添加木屑显著增加了土壤N(17.1%)、P(37.6%)含量,显著增加了微生物生物量碳(118.0%)、氮(41.0%)、磷(176.6%)。C、N、P获取酶(β-1,4-葡萄糖苷酶、β-1,4-N-乙酰氨基葡萄糖苷酶、亮氨酸氨基肽酶、酸性磷酸酶)活性总体上随添加有机物C/N值(生物炭<蒙古栎叶<油松叶<玉米秸秆<木屑)的增加而增加,其化学计量变化受土壤养分状态及微生物生物量的调控。酶活性相对比例及矢量特性表明,研究区微生物生长受到P的限制,且添加有机物没有缓解P的制约作用。微生物生物量碳、氮及化学计量比C∶N、C:P、N∶P属于绝对稳态型,而微生物生物量磷处于非稳态。微生物通过改变酶的分配策略保持微生物体元素及比例的相对稳定,仅有微生物生物量磷对土壤养分变化表现出不稳定性,可能因为P是研究区微生物生长的限制性元素。