传统稻鱼系统生产力提升对稻田水体环境的影响

如何在提升传统农业系统生产力的同时又不破坏其内涵、还对环境不产生负面影响,是一个受到研究者持续性关注的挑战性课题。本研究以具有1 200年历史的全球重要农业文化遗产稻鱼系统为例,研究稻鱼系统鱼的放养密度对生产力和环境的影响,探讨能够显著提升稻鱼系统生产力且又不破坏其传统性(产品优质、环境友好)的途径。研究表明,传统稻鱼系统(RF)(田鱼目标产量375 kg.hm 2)与水稻单作系统(RM)水体的化学需氧量(COD)、总氮(TN)、总磷(TP)及铵态氮(NH4+-N)含量均没有显著性差异。随着田鱼养殖密度提高(鱼产量由750 kg.hm 2提高到3 000 kg.hm 2)和饲料投入的相应增加,稻鱼系统的生产力和经济产出大幅度提高(稻鱼系统的净经济收入增加25.2%~101.4%),但稻鱼系统(RF)水体的COD值及TN、TP和NH4+-N含量均呈现增加的趋势,尤其是当鱼目标产量增至3 000 kg.hm 2时,水体TP含量和COD值显著提高,面源污染风险增加。分析还表明,鱼放养目标产量为2 250 kg.hm 2时,稻鱼系统经济效益最佳,此时净经济收入比传统稻鱼系统增加55.9%,并且不会对水体环境质量产生负面影响。     

利用航空成像光谱数据研究土壤供氮量及变量施肥对冬小麦长势影响

以推扫式成像光谱仪PHI(Pushbroom Hyperspectral Imager)获取的冬小麦拔节期、灌浆初期及乳熟期的航空影像数据为基础，提取反映冬小麦长势的光谱特征值，结合地面调查数据，分析了研究区冬小麦的长势情况；对不同时相光谱特征值与土壤基础供氮量、土壤总供氮量以及变量施肥量进行统计分析，分析结果显示：土壤基础供氮量、土壤总供氮量的空间分布差异对冬小麦长势有明显的影响，其中，土壤基础供氮量是影响冬小麦长势的重要因素，它对冬小麦的长势影响贯穿冬小麦的整个生育期；此外，该文还通过变量施肥前后作物     

我国农田氮肥施用现状、问题及趋势

氮素在作物产量和品质形成中起着关键作用。本文综述了什么是合理施氮,包括施氮量、施氮方法和时期,也包括与有机肥和秸秆还田措施的配合等。指出我国农田氮肥施用的主要问题是施肥过程和施肥后的严重损失。依据农户调查所获得的田块尺度施氮量,与田间试验合理施氮量对比分析表明,过量施氮田块占总调查田块的大约33%。依据区域尺度单位播种面积平均施氮量,与作物平均推荐施氮量对比分析表明,全国过量施氮面积占播种面积20%、合理面积占70%、不足面积占10%。总体而言,过量施氮现象还相当普遍,特别是在蔬菜和果树等经济作物上。本文提出了一种估算国家尺度氮肥需求量的方法,可估算出全国合理需氮量范围,称之为氮肥需求量估算法。用三种不同方法估算的我国1980~2010年间的氮肥需求量与实际氮肥使用量比较表明,如仍然依照现在的粗放施肥习惯,应该为现在的实际氮肥使用量,5年平均为N 27.9×106t左右,正好处于合理需氮量范围的中线。在改善施肥技术基础上,我国2006~2010年间5年氮肥平均使用量应该在N 19.6×106t左右;用五种方法预测的我国未来氮肥需求量表明,如果改善施肥技术,我国2020、2030、2050年合理氮肥需求量分别为N 21.0×106t、21.7×106t、23.1×106t;如施肥技术得不到实质性改善,依然粗放施氮,则氮肥需求量应处于合理使用量范围的中线,分别为N 30.4×106t、31.4×106t、33.4×106t。进一步分析了我国粮食产量和氮肥施用量与美国和西欧的差异,我国农田有机肥和碳投入对增加土壤有机碳氮库的重要性。     

新型分层生物滴滤池去除污水中氮磷的性能研究

生物滴滤池是农村生活污水处理的主要技术之一,但其存在氮、磷去除能力有限,稳定性不高等缺点。为提高新型分层生物滴滤池的氮磷去除效率,探索最佳工艺条件,本文采用新型分层生物滴滤池为试验装置,考察了滤料种类、水力负荷、回流比等对装置去除污水中氮磷性能的影响。结果表明,当滤料为炉渣、水力负荷为4 m3·m-2·d-1、回流比为2∶1时滤池去除氮磷的效果最好,对NH4+-N、TN、TP、COD的平均去除率分别可达到87.08%、57.37%、66.04%、80.78%;采用较高的回流比是滴滤池提高脱氮效果的一条有效途径。     

Significant Nitrogen by Sulfur Interactions Occurred for Canola Grain Production and Oil Concentration in Grain on Sandy Soils in the Mediterranean-Type Climate of Southwestern Australia

The nitrogen (N) by sulfur (S) interaction for canola (Brassica napus L.) grain production and oil concentration in grain has been quantified in temperate climates, but it is not known if these results also apply to sandy soils common in the Mediterranean-type climate of southwestern Australia where canola is now a major crop. Seventeen field experiments were undertaken with canola in the region during 1994 to 2005 in which 4 rates of both N (0–138 kg N/ha) and S (0–34 kg S/ha) were applied. Significant grain yield responses to applied N occurred in all experiments and the responses increased as more S was applied. Grain yield responses to applied S only occurred when N was applied and tended to increase as more N was applied. When no S was applied the two largest rates of N applied, 69 and 138 kg N/ha, induced S deficiency reducing grain yields. The oil concentration in grain tended to decrease as more N was applied and increased as more S was applied, particularly when the two largest rates of N were applied. Consequently significant N × S interactions were obtained in all experiments for grain production and in 15 experiments for oil concentration in grain.     

INFLUENCE OF NITROGEN AND SULFUR ON YIELD AND SEED QUALITY OF THREE CANOLA CULTIVARS

In order to investigate the effect of nitrogen (N) and sulfur (S) fertilizers on yield and seed quality of three canola cultivars, a factorial based on randomized complete block experiment was conducted during 2005–2006 in Iran. Treatments included four nitrogen rates (0, 75, 150, and 225 kg N ha^?1 source of urea), four sulfur rates (0, 100, 200, and 300 kg S ha^?1), and three cultivars (‘Pf’, ‘Option-500’, and ‘Hyola-401’). Results indicated cultivar had a significant effect on all studied traits. ‘Option-500’ and ‘Hyola-401’ cultivars had the highest seed yield, protein content, and N:S ratio in seed. The levels of 150 and 220 kg N ha^?1 resulted in the maximum protein content. Increasing N levels resulted in N content and decreased the oil content. The interaction effect between S and N levels showed the highest N content in seed was obtained with 300 kg S ha^?1 and 225 kg N ha^?1.     

MYCORRHIZAL INFLUENCE ON FRUIT YIELD AND MINERAL CONTENT OF TOMATO GROWN UNDER SALT STRESS

Tomato (Lycopersicon esculentum Mill.) yields are known to decrease for plants grown in saline soils. This study was conducted to determine the effects of arbuscular mycorrhizal fungi (AMF) inoculation on fruit yield and mineral content of salt-tolerant and salt-sensitive tomato cultivars grown with varied levels of salt. NaCl and CaCl₂were added to soil in the irrigation water in equal molar ratios to give EC_e values of 1.4 (nonstressed) and 4.9 dS m^?1 (salt stressed). Plants were grown in a greenhouse using unsterilized, low phosphorus (P) (silty clay) soil-sand mix. Mycorrhizal root colonization occurred whether cultivars were salt stressed or nonstressed, but the extent of AMF root colonization was higher in AMF inoculated than uninoculated plants. The salt tolerant cultivar ‘Pello’ generally had higher AMF root colonization than the salt sensitive cultivar ‘Marriha’. Shoot dry matter (DM) yield, fruit fresh yield, and AMF colonization were higher for plants grown under nonstressed than for plants grown under salt stressed conditions. Shoot DM and fruit fresh yields were higher in AMF inoculated than uninoculated plants grown with or without salt stress. Pello generally had higher fruit fresh yield per plant and fruit weight than Marriha, but these differences were only significant for fruit weight in unioculated plants grown under salt stressed conditions. The enhancement in fruit fresh yield due to AMF inoculation was 26 and 23% under nonstressed and 28 and 46% under salt stressed treatments for Pello and Marriha, respectively. For both cultivars, fruit contents of P, potassium (K), zinc (Zn), copper (Cu), and iron (Fe) were higher in AMF inoculated compared with uninoculated plants grown under nonstressed and salt stressed conditions. Fruit Na concentrations were lower in AMF inoculated than uninoculated plants grown under salt stressed conditions. The enhancement in P, K, Zn, Cu, and Fe acquisition due to AMF inoculation was more pronounced in Marriha than in Pello cultivar under salt stressed conditions. The results of this study indicated that AMF inoculated plants had greater tolerance to salt stress than unioculated plants.     

表皮生长因子在动物肠道无机离子及其他营养物质吸收中的作用

表皮生长因子(epidermal growth factor,EGF)是生长因子家族成员之一,具有促进细胞生长、细胞迁移、细胞增殖、伤口愈合、骨骼愈合以及营养物质转运等生物学功能。大量研究表明EGF对钠离子、氯离子、镁离子、无机磷、葡萄糖、谷氨酰胺、小肽、5-羟色胺等物质的转运具有促进作用。本文旨在概述EGF对营养物质转运的影响,为EGF在动物生产上的应用提供参考。     

沼肥替代化肥对设施蔬菜产量和土壤养分及重金属累积的影响

针对盲目施用沼肥可能带来的土壤环境问题,该研究采用5年8茬的设施番茄-甜椒田间轮作试验,研究不同沼肥和化肥配比对蔬菜产量、设施土壤氮磷养分及重金属累积的影响.结果表明:在等氮钾养分投入下,沼肥和化肥以不同比例配施的各处理没有影响蔬菜产量;氮素盈余和0~180cm土层土壤全氮含量随沼肥施用比例增加没有显著差异;磷素盈余随沼肥施用比例增加显著增加,完全沼肥处理0~30cm土层土壤Olsen-P及CaCl2-P含量分别达到151和8.0mg/kg,高于其他2个处理,且明显超出环境阈值.与完全沼肥处理相比,减量沼肥施用(3/5沼肥处理)明显降低了土壤氮素淋洗风险和磷素累积.与不施肥处理相比,施用沼肥后30~60、60~90、150~180cm土层土壤全Hg含量均低于不施肥处理;除30~60cm土层使用沼肥处理土壤中全As含量显著高于不施肥处理,其他土层各处理间均没有显著差异,而完全沼肥处理全Cr、全Cd、全Pb含量有所下降,且全Pb含量下降最为显著,但均没有出现重金属污染风险.沼肥替代化肥施用可有效实现废弃物中的养分资源循环利用,但增加菜田土壤磷素累积和淋失风险,本研究为设施菜田合理施用沼肥提供技术支持,为实现沼肥资源的循环利用和化肥替代模式提供理论参考.