再生水滴灌对滴头堵塞的影响

研究以再生水（二级处理出水）为灌溉水源时,3种滴头（单翼迷宫式滴头、内镶式滴头和压力补偿孔口式滴头）的流量、灌水均匀度和堵塞的变化过程及规律,并和自来水灌溉条件下的结果进行对比,分析了滴头堵塞的主要原因。研究结果显示：再生水灌溉条件下3种滴头的流量和灌水均匀度都要明显小于自来水条件下的结果,其中单翼迷宫式滴头的流量和灌水均匀度下降最大,而压力补偿孔口式滴头的变化最小。水质和滴头内沉淀物质的分析显示,化学沉淀（主要成分为CaCO3和MgCO3）是引起滴头堵塞的主要方式,滴头流量小、流道尺寸小和流态指数偏高也增加了滴头堵塞的风险。建议实际中利用再生水灌溉的滴灌系统,可选用压力补偿孔口式滴头。     

Effects of different soil management practices on total P and Olsen-P sediment loss: A field rainfall simulation study

Field rainfall simulations were conducted in 2002 and 2005 to study the effects of different soil management practices on the total phosphorous (TP) and Olsen-P losses by soil erosion and redistribution along a 15 m long slope in Luoyang, Henan province, China. Field plots were set up in 2001 and included the following soil management practices: subsoiling with mulch (SSM), no-till with mulch (NTM), reduced tillage (RT), and a conventional tillage control (CT). The results showed that there were no significant differences in TP and Olsen-P content in the sediment load between different plots after 6 years uniform tillage practices. The enrichment of TP and Olsen-P at the lower slope showed a clear redistribution along the slope. Effects of tillage practices on the temporal pattern of the enrichment ratio (ER) of TP and Olsen-P was not uniform. ER_TP values were initially high and diminished after a short period of time and leveled to the end of the rainfall test in CT and RT plots, but remained ≥ 1. The ER of Olsen-P at the end of rainfall simulation showed a significant difference when compared to the initial stage, 0.78 to 1.60, respectively. However, the temporal loss rate of TP and Olsen-P showed a similar pattern because it was more depending on the sediment loss rate than on the concentration in the sediment. SSM resulted in 96% less TP and Olsen-P erosion loss compared to CT in 2002. Also, SSM showed the highest reduction in TP and Olsen-P loss after 4 years consistent practice. RT reduced TP and Olsen-P loss by 30%, although the runoff reduction was not significant. NTM was the best alternative with respect to TP and Olsen-P conservation, when considering its lower operational costs.     

Effects of delayed first feeding on the survival and growth of tiger grouper,Epinephelus fuscoguttatus (Forsskål, 1775), larvae

The effects of delayed first feeding on the survival and growth of tiger grouper, Epinephelus fuscoguttatus (Forsskål 1775), larvae were examined under controlled conditions. The total length, yolk sac volume, oil globule volume, yolk sac absorption time and nutritional transition period (NTP) of the larvae fed at different first times (0, 6, 12, 18 and 24 h after the mouth opening stage; h AMO) were compared. Larval first feed intake was observed at 54 h after hatching (h AH) at 27.5 ± 0.5 °C. The yolk sac was consumed more rapidly with an increase in delayed first feeding and was significantly different among treatments (P<0.05). Larvae first fed at 0 h AMO had the longest yolk sac absorption (72 h AH) and NTP (20 h) times and had the highest survival and growth rates at the end of the experimental period (360 h AH), being significantly higher (P<0.05) than the other treatments. First mortality was observed at 69 h AH, approximately 2 h after point of no return (PNR) occurred. This study suggests that first feeding of tiger grouper larvae should commence at 0 h AMO for enhancement of larval survival and growth.     

烟田油菜免耕直播不同密度研究

为探讨烟田油菜免耕适宜密度,以行距为固定的烟垄行、穴距为33.33 cm,穴定植留苗2株、3株、4株、5株4种不同定植密度,进行了烟田油菜免耕直播试验研究.结果表明,烟田油菜免耕直播最佳密度,在现有施肥水平和管理条件下,以穴定植3株,定植密度6000株/667m2最佳.     

回流滴灌系统泥沙输移及抗堵塞性能研究

为探究在传统支状滴灌系统末端设置回流管后滴灌系统毛管主流流速增加后回流滴灌系统的输沙排沙潜力及其抗堵塞性能,通过周期滴灌实验分析回流滴灌系统的灌水均匀系数以及滴头堵塞情况,并对毛管内沉积泥沙分布特点和系统各部分输沙排沙所占比重进行分析。实验结果表明:0.035 m·s~(-1)回流、0.05 m·s~(-1)回流滴灌系统的灌水均匀系数、滴头堵塞数量均明显优于支状滴灌系统。回流流速为0.05、0.035、0.015 m·s~(-1)三种回流系统中毛管沉泥量依次增加,但均低于支状滴灌系统的毛管泥沙沉积数量,同时四种回流滴灌系统均表现为沿水流方向毛管内沉泥量逐渐增加。支状滴灌系统、0.015 m·s~(-1)回流、0.035 m·s~(-1)回流、0.05 m·s~(-1)回流系统回流排沙量分别为0、1.59、4.30、7.52 kg,表明回流管具有良好的输沙排沙能力。     

大蒜应用免深耕土壤调理剂试验初报

应用免深耕土壤调理剂对大蒜进行试验研究,结果表明,免深耕土壤调理剂在大蒜上应用能提高肥效,促进大蒜植株生长,对大蒜的抗病性和抗逆性具有一定作用,每667m2增产96.3～171.2kg,增产15.9%～28.2%。     

黄河水沉淀后水质对滴灌灌水器堵塞的影响

利用2013年5月—10月和2014年7月—11月的实测数据,分析了乌海市不同功能的三个典型沉淀池(如意湖、林业湖和朝阳湖)的浊度、细菌总数、叶绿素a、总氮、总磷五项水质指标的沉淀、过滤效率,利用灌水器堵塞野外调查数据并结合堵塞物电镜扫描图片,探讨了黄河水经过平流沉淀+网式过滤组合模式处理后仍会造成灌水器堵塞的原因。结果表明:各沉淀池浊度的沉淀和过滤效率均较高,其中如意湖的沉淀效率最高,平均去除率为63%;2013年朝阳湖的过滤效率最高,为60.53%,各沉淀池水质指标的过滤效果普遍较差。黄河水经沉淀过滤后仍会造成灌水器堵塞,其主要原因与细小颗粒物和微生物形成的絮状结构有关,建议对原有沉淀、过滤措施提出改进,经一、二级沉淀后在泵房内改用叠片式砂过滤器。     

免耕与常规耕作潮棕壤交换性阳离子的剖面分布特征

通过田间定位试验.研究了不同耕作方式对潮棕壤0-100 cm深度6个土层土壤交换性阳离子的影响.结果表明,与常规耕作相比,免耕使土壤表层pH显著增,.而电导率下降;同时,免耕增加了表层土壤可交换性K~+含量,降低了可交换性Na~+含量,但对可交换性Ca~(2+),Mg~(2+)和阳离子交换量没有产生显著影响.相关分析结果表明,可交换性K~+与土壤养分含量没有显著相关性,而可交换性Na~+,Ca~(2+),Mg~(2+)和阳离子交换量与有机质和全氮含量均呈负相关关系.     

黄鳝仔鱼饥饿试验与不可逆点的确定

【目的】确定黄鳝（Monopterus albus）的初次摄食期和不可逆点（PNR）,为提高人工繁育黄鳝苗成活率和饵料利用率提供理论依据。【方法】对刚出膜黄鳝仔鱼分别进行饥饿试验和正常投喂试验,观察卵黄囊吸收、仔鱼生长及初次摄食率的变化,分析饥饿对仔鱼生长、形态和行为的影响,确定其不可逆点。【结果】在25～28℃的水温条件下,黄鳝仔鱼于5日龄（出膜后第6d）开始向外界摄食,8日龄卵黄囊吸收殆尽,5～8日龄为混合营养阶段,9日龄摄食率达到峰值（96%）,16日龄进入饥饿期;在饥饿状态下,8日龄仔鱼体长达最大值（3.20±0.0760cm）,此后略有下降但基本保持稳定,仔鱼体重于7日龄达最大值（0.0205±0.0533g）,此后不断下降;饥饿仔鱼的肥满度一直呈下降趋势,进入不可逆期后体色逐渐发黑,身体呈非正常扭曲,摄食能力极大降低,外界干扰时出现颤抖、打转现象直至死亡。【结论】在25～28℃的水温条件下,黄鳝仔鱼的最佳投喂时机在8日龄,16日龄抵达不可逆点。     

Nitrogen for no‐tillage corn in Virginia: Sources and time of application

Abstract

No‐tillage corn (Zea mays L.) culture normally entails the placement of N fertilizer on the soil surface without mechanical incorporation. This field investigation was conducted to compare the N fertilizers that are most widely used in Virginia, when applied in this manner, for their effectiveness in producing notillage corn. Comparisons of the time of applying NH₄NO₃ were also made. Grain and stover yields, in addition to N removed in the crop, were used to draw conclusions. The experiments were conducted on both fertile and infertile soils in 1972 and 1973, both of which were relatively wet years. The fertilizers tested, urea, NH₄NO₃, and N solutions, were equally effective, per unit of N applied. Split applications of NH₄NO₃ showed no statistically significant advantage over all applied at planting but slightly trended to do so. N deficiency reduced grain yields relatively more than stover yields.