无功就地补偿技术在农业排灌泵站中的应用

目前农业排灌站普遍存在功率因数低、无功损耗大的情况.无功就地补偿技术,可以有效地提高供配电系统的功率因数,达到节能的效果.为此,针对6kV配电站的补偿方式进行了仿真分析,论证了在排灌泵站中采用无功就地补偿技术的经济可行性,并对推广该技术存在的问题,提出了一些建议.     

Empirical analysis and prediction of nitrate loading and crop yield for corn-soybean rotations

Nitrate nitrogen losses through subsurface drainage and crop yield are determined by multiple climatic and management variables. The combined and interactive effects of these variables, however, are poorly understood. Our objective is to predict crop yield, nitrate concentration, drainage volume, and nitrate loss in subsurface drainage from a corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) rotation as a function of rainfall amount, soybean yield for the year before the corn-soybean sequence being evaluated, N source, N rate, and timing of N application in northeastern Iowa, U.S.A. Ten years of data (1994-2003) from a long-term study near Nashua, Iowa were used to develop multivariate polynomial regression equations describing these variables. The regression equations described over 87, 85, 94, 76, and 95% of variation in soybean yield, corn yield, subsurface drainage, nitrate concentration, and nitrate loss in subsurface drainage, respectively. A two-year rotation under average soil, average climatic conditions, and 125 kg N/ha application was predicted to loose 29, 37, 36, and 30 kg N/ha in subsurface drainage for early-spring swine manure, fall-applied swine manure, early-spring UAN fertilizer, and late-spring split UAN fertilizer (urea ammonium nitrate), respectively. Predicted corn yields were 10.0 and 9.7 Mg/ha for the swine manure and UAN sources applied at 125 kg N/ha. Timing of application (i.e., fall or spring) did not significantly affect corn yield. These results confirm other research suggesting that manure application can result in less nitrate leaching than UAN (e.g., 29 vs. 36 kg N/ha), and that spring application reduces nitrate leaching compared to fall application (e.g., 29 vs. 37 kg N/ha). The regression equations improve our understanding of nitrate leaching; offer a simple method to quantify potential N losses from Midwestern corn-soybean rotations under the climate, soil, and management conditions of the Nashua field experiment; and are a step toward development of easy to use N management tools.     

晒田强度和穗肥运筹对三角形强化栽培水稻光合生产力和氮素利用的影响

以杂交中稻组合II优498为材料,在三角形强化栽培(TSRI)条件下,研究3种晒田强度(0~20 cm土壤相对含水量为80%±5%、60%±5%和40%±5%,分别记为W₁、W₂和W₃)和3种穗肥运筹(晒田复水后第1、8和15天施用第1次氮素穗肥,分别记为S₁、S₂和S₃)对灌浆结实期水稻光合生产和氮素利用的影响。结果表明,晒田程度和穗肥运筹对水稻光合生产、干物质积累、氮素积累、转运和利用和产量的影响存在显著互作效应,且晒田影响最为显著,氮素穗肥运筹次之。轻度晒田(W₁)复水后第1天施用第1次氮素穗肥会降低抽穗后15 d和30 d的群体光合和有效穗数,推迟至复水后第8天或第15天施用第1次氮素穗肥可以提高抽穗后15 d和30 d的群体光合、收获指数和氮素稻谷生产效率;中度和重度晒田(W₂和W₃)复水后第1天和第8天施用第1次氮素穗肥可以提高孕穗期和齐穗期剑叶P_n和抽穗后15 d和30 d的群体光合、干物质积累、籽粒产量及构成指标、稻株氮素积累与利用。经过分析比较得出,TSRI模式下W₂S₁为晒田强度和穗肥运筹的最优组合,产量达到10.96 t ha^-1。     

典型断面渠道临界水深计算

系统总结了明渠特征水深研究领域的计算方法,评价了各方法的特点;为了优选出典型断面渠道临界水深简捷、通用、精度高、适用范围广的显式计算公式,通过定义包含典型断面几何要素及流量的量纲为一的参数,将目前成果中临界水深的显式计算公式用定义量纲为一的参数进行统一表达,并对其进行简捷性、精度及适用范围的综合评价比较,优选出梯形、圆形、弧底梯形、普通城门洞形、马蹄形等5种典型断面渠道临界水深的显式计算公式;对标准城门洞形断面的临界水深应用最优一致逼近原理,提出以幂函数形式分段表达的新显式计算公式．误差分析表明,在工程常用范围内,由推荐的显式公式所计算的6种典型断面的临界水深,其最大相对误差均小于1％,满足工程设计对精度的要求．该研究可为典型断面排灌渠道的设计及水力计算提供参考．     

Practice to avoid contamination of drainflow and runoff from slurry spreading in spring

Abstract. Use of either three or six occasions to spread similar total amounts of slurry was investigated over the late winter/early spring period in two years, on plots with underdrainage. Slurry was spread on four 7 m by 25 m plots which were instrumented to allow collection of drainflow and runoff. The 'mobile water' pore space allowed transport of a small proportion of applied slurry through the 0.75 m soil profile. Evidence of a polluted 'mobile water' pulse occurred after periods of up to 48 hours following spreading, suggesting subsurface rather than overland flow. Timing of the pulse depended on whether subsequent rainfall accelerated the flow The contaminated flow persisted for 6–12 hours. The worst contamination of 39 mg/l NH₄⁺ -N occurred under 'bypass flow' conditions, when 52 mm of rain fell during the 48 hours after a 5.2 mm application. Two contributory factors appeared important. The first was the long duration of the high intensity storm and the second was an extended period of severe frost believed to have created fissures associated with frost heave. Making several applications of slurry in amounts less than 35 m³/ha is preferable to fewer larger applications during spring, for cereals on medium to heavy soils. This recognises the likelihood of there being underdrainage on arable land and the optimal use of well-drained, partially frozen ground to avoid compaction by slurry tankers.     

工业生产系统环境污染治理理念的探讨

随着世界经济的发展，地球环境日趋恶化。为了人类的生存和发展，必须实施可持续发展战略。文章在分析工业生产系统环境污染产生的原因和过程末端治理弊端的基础上，提出了从源头治理环境污染的理念——宏观上依据热力学第二定律，在中观上采用工业生态学原理，在微观上实施绿色制造和清洁生产，即从客观上运用熵、工业生态学、清洁生产和绿色制造的理论调配资源，组织工业企业，进行生产。最后对排灌机械的可持续发展战略的实施进行了探讨。     

Evaluating a multi-level subsurface drainage system for improved drainage water quality

This paper describes a multi-level drainage system, designed to improve drainage water quality. Results are presented from a field scale land reclamation experiment implemented in the Murrumbidgee Irrigation Area of New South Wales, Australia. A traditional single level drainage system and a multi-level drainage system were compared in the experiment in an irrigated field setting. The single level drainage system consisted of 1.8 m deep drains at 20 m spacing. This configuration is typical of subsurface drainage system design used in the area. The multi-level drainage system consisted of shallow closely spaced drains (3.3 m spacing at 0.75 m depth) underlain by deeper widely spaced drains (20 m spacing at 1.8 m depth). Data on drainage flows and salinity, water table regime and soil salinity were collected over a 2-year period.     

三江平原不同土地利用方式下沟渠沉积物可溶性有机碳含量和分布

研究了三江平原3种土地利用方式下沟渠沉积物DOC含量和分布,探讨了3种土地利用方式对沟渠沉积物DOC含量和分布的影响。结果表明,三江平原沟渠系统虽然都是在湿地的基础上开挖而成,但是分散于3种土地利用方式下的沟渠沉积物DOC含量及其分布发生了明显变化。湿地开垦为农田利于沟渠各层沉积物DOC的累积,水田和旱田相比,旱田更有利于沟渠各层沉积物DOC的累积;沟渠沉积物DOC垂直分布随土地利用方式不同发生了明显的变化,穿过型沟渠和边界沟渠相比,边界沟渠沉积物DOC垂直分布显示出更强的沉积特点。挖沟排水和土地开垦耕作,不仅导致大量DOC向沟渠迁移并沉积在沟渠中,而且最终导致不同沟渠沉积物中DOC的含量和分布产生了明显的差异性。     

紫色土坡耕地径流特征试验研究

通过具有壤中流观测功能的径流小区的定位观测,结合人工降雨模拟试验,对常规施肥条件下紫色土坡耕地径流特征、过程及影响因素进行长期监测。结果表明:(1)紫色土坡耕地地表径流过程呈多峰特征,受瞬时雨强的影响明显;而壤中流过程则表现出明显的单峰、产流时间滞后、持续时间长等特点;(2)玉米灌浆成熟-收割期径流量明显高于其它生育期,地表径流、壤中流径流量分别为(65.06±5.94)mm,(86.36±3.27)mm,分别占3年地表径流、壤中流年均径流量的67.92%,79.82%;(3)坡耕地地表径流和壤中流径流量与降雨量的相关性显著,但与降雨强度的相关性不显著。坡耕地地表径流系数随坡度的增加而增加,而壤中流径流系数随坡度的增加而明显降低。(4)坡耕地径流分配特征明显。3年地表径流年平均径流量为95.78 mm,壤中流平均流量为108.19mm,分别占总径流量的46.96%,53.05%。     

新疆棉田地下滴灌方式下土壤速效磷空间分布规律的研究

为探讨新疆棉田地下滴灌方式下土壤速效磷空间分布的规律,在棉花不同生育期采用 0.5 mol/L NaHCO3浸提-钼蓝比色法,从水平方向和垂直方向上测定棉田土壤速效磷(Olsen-P).研究分析后认为:垂直方向上,在棉花各生育期土壤速效磷含量的变化呈随着土层深度的增加而减小的趋势;随生育进程的推进,棉田各土层土壤速效磷呈逐渐下降的变化趋势 ;水平方向上,棉田各土层土壤速效磷的变化呈随着与滴灌带距离的增大而缓慢增加的趋势;随棉花生育进程的推进,水平方向土壤速效磷变化为逐渐减少的趋势.