田间便携式平底短喉道量水槽水力特性试验

为了探索研究灌区田间进水口的水量计量,该文在巴歇尔量水槽的基础上设计制作了一种体型简单、成本低的田间便携式平底短喉道量水槽,喉口宽度51 mm、长度774 mm,便于携带和田间安装;通过试验研究了该量水槽的水力性能,观测了24种流量下量水槽内11个控制断面的水位,拟合得到自由出流和淹没出流条件下的水深与流量公式,与实测流量对比,平均相对误差和最大相对误差均在10%以内,满足灌区田间量水精度要求;分析了不同流量下佛汝德数、断面比能沿槽身各控制断面的变化规律,确定临界水深断面位于该量水槽喉口段的中部偏后段;分析了槽内水头损失情况,得知该量水槽最大水头损失占上游总水头的12.10%,相较于长喉道量水槽较小,自由出流条件下槽内水头损失小于淹没出流条件下0.02倍上游总水头。该研究为田间进水口量水设施在中国北方灌区末级渠系的进一步应用提供参考。

Research on Modification of Non-limiting Water Range of Soil

[Objective] The paper was to study and modify non-limiting water range （NLWR） of soil. [Method] The water content when total soil water potential was -0.3 MPa or soil mechanical resistance was 0.85 MPa was selected as the lower limit of NLWR to replace the original water content of permanent wilting point or the water content under soil mechanical resistance of 2.0 MPa. NLWR could be calculated us-ing the minimum value of upper limit minus the maximum value of lower limit. [Re-sult] Compared with original NLWR or least limiting water range （LLWR）, the modi-fied NLWR had more practical significance. When Db〉Db-thr, soil physical properties hindered the growth of crops, so the soil should be improved; when Db〉Db-thr, soil physical properties hindered the growth of crops, so-the soil should be improved; wtlen Db〈Db-thr, as long as the soil water content is within NLWR, soil physical properties had no effect on crop growth. NLWR at this time could be used as the basis for irrigation man- agement in farmland. [Conclusion] The study provides theoretical support and scientific basis for relevant researches about evolution rule and regulatory mechanisms of soil physical quality, relationship between soil physical quality and crop growth and yield, water-fertilizer-salt management of soil.

Field Capacity in Black Soil Region, Northeast China

In this work, 23 black soil profiles were surveyed and 113 soil samples were collected to determine the field capacity (FC) of the black soil in Northeast China. The effectiveness of three methods measuring FC, the Wilcox method (WM), the undisturbed soil pressure plate method (PUM) and the air-dried sieved soil pressure plate method (PDM) were compared to select a suitable laboratory measurement method. Results show that the FC values measured by PDM are greater than those measured by PUM, and the values measured by PUM are greater than those measured by WM. PUM is more suitable for the determination of FC in the study area. One regression equation between PUM and PDM has been established through which undisturbed soil can be replaced by air-dried sieved soil, which is easier to get, to measure FC. FCs vary from 23.50% to 37.00%, with an average of 31.65%, which differ greatly among the 23 black soil profiles. FC is found to be significantly positively correlated with the silt content, clay content and bulk density of the soil, but significantly negatively correlated with the sand content. An empirical pedotransfer function is established to estimate the FC using available soil physical and chemical properties.

Morpho-Anatomical Changes in Roots of Chickpea （Cicer arietinum L.） under Drought Stress Condition

Chickpea （Cicer arietinum L.） is a crop cultivated in semi-arid and rainfed areas of Pakistan and it experiences terminal drought stress. In this paper, the morpho-anatomical study regarding roots of chickpea was carried out to investigate the drought adaptation strategies. Twelve cultivars of chickpea were grown in pots under drought stress of 70% and 35% field capacity in addition to control （100%）. Root segments of mature chickpea plants were sectioned in 2 cm from root-shoot junction and used for making transverse sections. The development of sleeve and stele tissues and their proportion were markedly influenced by moisture availability to the root system. Roots length, flesh and dry weight, and number of secondary roots were decreased under field capacity of 70% and 35% as compared to control in 12 cultivars of chickpea. Root epidermis and cortex of CH47/04 consisted of cells with thickened walls and with 2-3 cell layers of sclerenchymatous cells below the epidermis. Increased number of medullary rays and high vascular region was observed in cultivars CH120/04, CH47/04, CH587/05 and CH87/02. Anatomical studies showed that CH47/04 was highly tolerant among 12 cultivars of chickpea, while CH587/05 and CH87/02 behaved moderately under both levels of drought stress （70% and 35% field capacity）.

Effect of Deficit Irrigation at Different Growth Stages on Wheat Growth and Yield

In order to evaluate the effect of deficit irrigation at various growth stages on wheat growth and yield, a field experiment was conducted in the 2008-2009 growing season based on the completely randomized block with four replications at the experimental farm of the College of Agriculture, Shiraz University, Shiraz, Iran, located at Badjgah. Treatments involved 13 irrigation regimes which applied in stem elongation, heading and grain filling growth stages. The highest seed yield （4,333 kg-ha-1） and the lowest ones （1,377 kg＇hal） were obtained from T1 （100% field capacity （FC） in all growth stages） and T13 （50% FC in all growth stages）, respectively. With limitation in water amount seed yield was diminished, but this trend was not significant at T4 （100%, 100% and 50% FC） and TI 1 （100%, 100% and 75~/0 FC）. Stepwise regression results revealed that, seed number per spike had the largest contribution （partial R2 = 0.72） in seed yield variation. Also at TI, T4, and TI 1 treatments （well water treatments） as well as TI3 （sever stress） head number m2 contribute most in seed yield determination （partial R2 = 0.96）. It can be concluded that water shortage during the grain filling period and its allocation to the other consecutive crop, can increase crop production in southern regions of Iran.

Analysis of Soil Water Dynamics in a Tropical Rain Forest Soil （Arinic lixisol）, Abeokuta, Nigeria

Soil water dynamics in the dominant lwo soil series （Arinic lixisol） were evaluated at the Federal University of Agriculture, Alabata, Abeokuta, Nigeria. Field capacity, infiltration and water retention characteristics were evaluated in situ for a period of 161 d in the dry season for two root zone depths. Results show that the Iwo soil series has a field capacity ranging from 2.6%-5.5% at 0-45 cm and 45-90 cm root zone depths, respectively. The soil is quick draining with high infiltration rate and very poor water retention capacity confirming that the soil will require a short irrigation interval of about 2-3 d since available water for plant growth in predominantly sandy soils ranges between 2%-8%. Based on the foregoing, sprinkler irrigation is best suited for the lwo soil series, it should, however, be noted that the water application rate must be less than the infiltration rate of the soil in order to prevent surface ponding and runoff. A multivariate model relating soil moisture content with soil moisture tension and soil temperature calibrated within the study had very low model accuracy of 56% and 45% for the two root zone depths, respectively, implying the need for further studies.

Drought and N Addition in the Greenhouse Experiment： Blue Grama and Western Wheatgrass

Understanding how the growth of two key native grass species of the Northern Great Plains （Western wheatgrass and blue grama） may be affected under drought and nitrogen deficiency is essential for future management of these grasslands. The random complete block experimental design greenhouse study examined the effects of water and N addition on above-ground and below-ground harvested biomass of C3 （Western wheatgrass, WWG） and C4 （blue grama, BG） grass species for the purpose of gaining better understanding of drought responses for these two species. Compared with well-watered treatment （field capacity）, two water limited treatments （70% and 85% field capacity） decreased plant above- and below-ground biomass （WWG and BG）. For two N treatments （no N added, addition of 100 mg N kg^-1soil）, addition of N significantly improved plant above- and below-ground biomass of WWG and BG under water field capacity. Both above- and below-ground biomass of the two grass species increased linearly with increasing water supplied, but above- and below-ground biomass of WWG was always lower than BG for the same treatments （water or N addition）. The results demonstrated that BG seedlings had better adaptation than WWG to deal with the imposed drought or N deficient conditions.