排序方式： 共有51条查询结果，搜索用时 734 毫秒
1.
Seed presoaking improves wheat germination under marginal moisture conditions. The duration of seed presoaking was studied at The University of Arid Agriculture, Rawalpindi, using 10 wheat varieties. Seed presoaking beyond 12 h does not improve germination further, and beyond 21 h, germination rate is drastically reduced. 相似文献
2.
Food security is a high priority issue on the Chinese political agenda. China’s food security is challenged by several anthropogenic, sociopolitical and policy factors, including: population growth; urbanization and industrialization; land use changes and water scarcity; income growth and nutritional transition; and turbulence in global energy and food markets. Sustained growth in agricultural productivity and stable relations with global food suppliers are the twin anchors of food security. Shortfalls in domestic food production can take their toll on international food markets. Turbulence in global energy markets can affect food prices and supply costs, affecting food security and poverty. Policy safeguards are needed to shield food supply against such forces. China must make unremitting policy responses to address the loss of its fertile land for true progress towards the goal of national food security, by investing in infrastructure such as irrigation, drainage, storage, transport, and agricultural research and institutional reforms such as tenure security and land market liberalization. The links between water and other development-related sectors such as population, energy, food, and environment, and the interactions among them require reckoning, as they together will determine future food security and poverty reduction in China. Climate change is creating a new level of uncertainty in water governance, requiring accelerated research to avoid water-related stresses. 相似文献
3.
Changes in the bone mineral content (BMG) during the first 4 lactations were continuously studied between July 1977 and February 1982 in a total number of 103 dairy cows of different breeds and rearing intensities. The BMG was measured by dichromatic photon absorptiometry in 2 coccygeal vertebrae. Although great individual variations were found, the changes in BMG during the lactation followed a typical pattern with high values during the dry period and low values after calving and during mid-lactation. The influence of body weight on the BMC value is discussed. The changes in BMC were more accentuated during the first lactation, as compared to the subsequent lactations. This could indicate a metabolically more active skeleton in younger cows. In this study no difference in BMC pattern was observed between cows affected or not affected by parturient paresis. 相似文献
4.
Shahbaz Khan Muhammad Nadeem Asghar Tariq Rana 《Water, air, and soil pollution》2007,182(1-4):131-148
Automated synoptic weather typing and robust orthogonal stepwise regression analysis (via principal components analysis) were applied together to develop within-weather-type air pollution prediction models for a variety of pollutants (specifically, carbon monoxide – CO, nitrogen dioxide – NO2, ozone – O3, sulphur dioxide – SO2, and suspended particles – SP) for the period 1974–2000 in south-central Canada. The SAS robust regression procedure was used to limit the influence of outliers on air pollution prediction algorithms. Six-hourly Environment Canada surface observed meteorological data and 6-hourly US National Centers for Environmental Prediction (NCEP) reanalysis data of various weather elements were used in the analysis. The models were developed using two-thirds of the total years for meteorological and air pollution data; the remaining one-third (randomly selected) was used for model validation. Robust stepwise regression analysis was performed to analytically determine the meteorological variables that might be used to predict air pollution concentrations. There was a significant correlation between observed daily mean air pollution concentrations and model predictions. About 20, 50, and 80% of the 80 prediction models across the study area possessed R 2 values ≥ 0.7, 0.6, and 0.5, respectively. The results of model validation were similar to those of model development, with slightly smaller model R 2 values. 相似文献
5.
Shahbaz Khan Hafeez ur Rehman Muhammad Ashfaq Wahid Muhammad Farrukh Saleem Mumtaz Akhtar Cheema Shahzad Maqsood Ahmed Basra 《Journal of plant nutrition》2016,39(12):1681-1687
The impact of soil (1, 2 kg ha?1) and foliar (100, 200 mg L?1) boron (B) with control (no B) was evaluated on phenology and yield formation of Camelina each applied at stem elongation and flowering stages. Foliar (200 mg L?1) or soil B (2 kg ha?1) resulted in earlier flowering and maturity, increased fruit bearing branches (19.68%), number of siliqua, seeds per siliqua (4.6%), biological yield (15%), seed yield (24%), harvest index (11.4%) and oil contents (23%) than no B. Increased fruit bearing branches, seed filled siliqua or seed numbers, harvest index and oil quality can be attributed to changes in dry matter accumulated of stem with simultaneous increase in siliqua dry weight with foliar or soil applied B. In crux, foliar (200 mg L?1) or soil applied (2 kg ha?1) B seems promising to improve seed and oil yield, harvest index of Camelina sativa under B deficient condition. 相似文献
6.
Tek Narayan Maraseni Shahbaz Mushtaq Jerry Maroulis 《Agricultural Water Management》2010,97(3):382-388
Enhancing water productivity is often recommended as a “soft option” in addressing the problem of increasing water scarcity. However, improving water productivity, particularly through water reuse, incurs additional investment and may result in increased greenhouse gas (GHG) emissions. In this study, we analysed the water productivity and GHG implications of water reuse through pumping groundwater and creek water, and compare this with gravity-fed canal irrigation in the Upper Pampanga River Integrated Irrigation System (UPRIIS) in the Philippines.Water productivity indicators show that water reuse contributes significantly to water productivity. For example, water productivity with respect to gross inflow (WPgross) with water reuse (0.19 kg grain/m3) is 21% higher than without water reuse (0.15 kg grain/m3). However, there is a tradeoff between increasing water productivity and water reuse as water reuse increases GHG emissions. The estimated GHG emission from water reuse (pumping irrigation) is 1.47 times higher than without water reuse (gravity-fed canal irrigation). Given increasing concerns about climate change and the need to reduce carbon emissions, we recommend that a higher priority be given to water reuse only in areas where water scarcity is a serious issue. 相似文献
7.
Efficient fish feeding is currently one of biggest challenges in aquaculture to enhance the production of fish quality and quantity. In this review, an information fusion approach was used to integrate multi-sensor and computer vision techniques to make fish feeding more efficient and accurate. Information fusion is a well-known technology that has been used in different fields of artificial intelligence, robotics, image processing, computer vision, sensors and wireless sensor networks. Information fusion in aquaculture is a growing field of research that is used to enhance the performance of an “industrialized” ecosystem. This review study surveys different fish feeding systems using multi-sensor data fusion, computer vision technology, and different food intake models. In addition, different fish behavior monitoring techniques are discussed, and the parameters of water, pH, dissolved oxygen, turbidity, temperature etc., necessary for the fish feeding process, are examined. Moreover, the different waste management and fish disease diagnosis techniques using different technologies, expert systems and modeling are also reviewed. 相似文献
8.
播期和密度对棉花叶柄和根系硝态氮含量的影响 总被引：2，自引：0，他引：2
为探讨大田棉花氮代谢随播期和密度的变化规律,选用华棉3109(G.hirsutum L.)于2014年在华中农业大学试验农场,采用裂区设计:播期(月-日)(S1,05-30;S2,06-14)为主区,密度(株·m-2)(D1,7.5;D2,9.0;D3,10.5)为副区,研究了硝态氮含量在主茎叶柄和根系的分布特点。结果表明:1)随生育进程推进,叶柄和根系硝态氮含量先升高后降低,初花期最高。2)主茎叶柄硝态氮含量随叶位变化,蕾期、初花期由上而下逐渐降低,第1叶最高;盛花期逐渐增高,第1叶和第4叶最高;不同生育时期棉花叶柄硝态氮含量在叶位间的下降幅度随播期推迟而降低,随密度增加先升高后降低。3)播期和密度对不同生育时期棉花叶柄和根系硝态氮平均含量的交互作用均显著,但播期和密度主效应影响不同:见花施肥前,随推迟播期,棉花叶柄硝态氮平均含量显著降低了42.9%,根系硝态氮平均含量显著升高了12.1%,增加密度对叶柄和根系硝态氮平均含量无显著影响。见花施肥后,随播期的推迟,叶柄硝态氮平均含量无显著性变化,初花期平均为5.05 mg·g-1,盛花期平均为2.62 mg·g-1;而根系硝态氮平均含量,初花期S1S2,盛花期S1S2;随密度增加,D1,D2与D3初花期叶柄和根系硝态氮平均含量均显著降低;盛花期叶柄硝态氮平均含量呈先升高后降低趋势变化,而根系硝态氮平均含量则与初花期相反,呈显著递增趋势。综上所述,晚播高密条件下,见花一次施肥后,推迟播期不改变棉花地上部叶柄硝态氮平均含量水平,适度增加密度有利于棉花叶柄维持较高的硝态氮含量,有利于为叶片氮代谢提供充足的底物。 相似文献
9.
Salih A. I. Sabiel Ibrahim Noureldin Shahbaz K. Baloch Sana Ullah Baloch Waseem Bashir 《Archives of Agronomy and Soil Science》2016,62(1):139-145
A field experiment was conducted to evaluate nine genotypes of sorghum grown for two consecutive cropping seasons in 2006 and 2007 under rain-fed conditions in a semiarid zone at the Research Farm of El Fasher Research Station, Sudan. The objective of the study was to assess genetic variability and heritability among sorghum genotypes using phenotypic morphological traits. A randomized complete block design with four replications was used for the experiment. The grain yield (kg ha?1), the number of heads/plant, followed by straw yield (kg ha?1) had the highest genotypic coefficients of variation in both seasons. High heritability (above 95%) was shown for plant height in both seasons. High genetic advance was reported in straw yield, 1000-grain weight and days to flowering in both seasons. Highly significant differences among genotypes were found for all characters. The high-yielding genotype was Adv-Edo-CWS (E-9) with grain yields of 2780.6 kg ha?1. Grain yield was significantly and positively correlated with straw yield (r = 0.91), number of heads/plant (r = 0.69), plant height (r = 0.53) and 1000-grain weight (r = 0.36). However, it was significantly and negatively correlated with days to 50% flowering (r = ?0.21). Based on their positive association with grain yield, the character’s straw weight, number of heads/plant, plant height and 1000-grain weight would be the preferable selection criteria for sorghum improvement program in the country. 相似文献
10.
Shahbaz Khan 《Paddy and Water Environment》2010,8(1):41-50
Waterlogging and salinity problems in major rice growing areas demand policies aimed at better management of land and water
resources. This process can be facilitated through regional scale spatially distributed hydrologic–economic models that capture
and integrate point scale processes at paddock, farm and irrigation area levels. The study develops an integrated hydrologic–economic
framework that integrates hydrologic and economic responses for social and common pool optimum management in the Coleambally
Irrigation Area, Australia. The results of hydrological-economic model indicate that the economic units with heavier soils
and shallow watertables with minimum groundwater out flows are the best economic locations for growing rice as the total crop
water requirements are minimised. Social and common pool optimum scenarios indicates, after accounting for externalities and
groundwater dynamics, the optimal net returns could be achieved in about 15 years. There was not much difference between social
and common pool optimum, however, common pool optimum show decline in net revenue after 23 years because of shallow watertable
rise within 2 m of the surface. The current rice growing policies are mainly based on the clay content of soils and rice water
use limits. This work has highlighted the importance of incorporating groundwater dynamics in deciding environmental policies
for growing rice. 相似文献