Maize hybrids less dependent on high plant densities improve resource-use efficiency in rainfed and irrigated conditions   总被引：4，自引：0，他引：4  

I.S. Tokatlidis  V. Has  V. Melidis  I. Has  I. Mylonas  G. Evgenidis  A. Copandean  E. Ninou  V.A. Fasoula   《Field Crops Research》2011,120(3):345

  相似文献   

Effects of Crop Density and Irrigation Management on Water Productivity of Rice Production in Northern Iran: Field and Modeling Approach     

《Communications in Soil Science and Plant Analysis》2012,43(17):2085-2099

Freshwater availability for irrigation decreases because of increasing demand from urban and industrial areas, degrading irrigation infrastructure, and water quality. The demanding for high production of rice with less water use is crucial for food supply. In this research, a field experiment was conducted during 2001 and 2002 to determine the effect of crop density on water productivity of rice crop. The study was carried out in a split-plot design with three plant spacings as subplots (20 cm × 20 cm, 15 cm × 15 cm, and 10 cm × 20 cm) and four different irrigation regimes (continuous submergence as the control and 100%, 75%, and 50% evaporation of pan) as main plots. To model the various water productivity components, the ORYZA2000 model was used. The comparison of model results with observed data was performed using different statistical methods. The results showed that the irrigation by 75% evaporation from pan evaporation and 20 cm × 20 cm crop size are the optimum irrigation method and crop density management.  相似文献   

Bacillus asahii comes to the fore in organic manure fertilized alkaline soils     

《Soil biology & biochemistry》2015

Organic manure (OM) fertilization has a profound impact on agroecosystems. However, little is known about temporal responses and roles of the specific soil microbial guilds involved in the increases of soil fertility and crop yield triggered by OM fertilization. To unravel these interactions, a series of fresh and archived soil samples from a fertilization experiment started in 1989 in North China Plain (NCP) was systematically investigated. Molecular assays of contemporary fresh samples unravel that Bacillus asahii responded most distinctly to OM fertilization, while no shifts in microbial community structure were observed between chemical fertilizations and the control without fertilization; a series of archived soil samples from 1989 to 2009 reveal that the indigenous B. asahii took 2–4 years to become specifically dominant and its ratio fluctuated between 40% and 72% during 20 years. Culture-dependent assessments of isolated B. asahii strain further indicate that its rise subsequently played a key role in the increases of both crop yield and soil fertility, especially via accelerating carbon and phosphorus cycling. This insight deepens our understanding of how OM impacts agroecosystems through soil microbial processes, and highlights the possibility of using archived microbial information as a reference to develop an efficient and sustainable agricultural strategy.  相似文献   

气候变暖对农作物物候、光合生理特性和产量影响的研究进展     

张丽霞  尹季显 《安徽农业科学》2015,(29)

目前,有关增温对农作物的影响研究主要集中在农作物的产量和品质等研究方面,其研究结果存在较大的不确定性.在此综述了近几十年来有关增温对不同农作物物候、光合生理特性和产量影响等方面的研究现状,在此基础上提出了未来需要加强的研究方向.  相似文献   

Crop management and phenology trends in the U.S. Corn Belt: Impacts on yields, evapotranspiration and energy balance   总被引：2，自引：0，他引：2  

William J. Sacks  Christopher J. Kucharik 《Agricultural and Forest Meteorology》2011,151(7):882-894

Crop yields are affected by many factors, related to breeding, management and climate. Understanding these factors, and their relative contributions to historical yield increases, is important to help ensure that these yield increases can continue in the future. Two important factors that can affect yields are planting dates and the crop's growing degree day (GDD) requirements. We analyzed 25 years of data collected by the USDA in order to document trends in planting dates, lengths of the vegetative and reproductive growth periods, and the length of time between maturity and harvest for corn and soybeans across the United States. We then drove the Agro-IBIS agroecosystem model with these observations to investigate the effects of changing planting dates and crop GDD requirements on crop yields and fluxes of water and energy. Averaged across the U.S., corn planting dates advanced about 10 days from 1981 to 2005, and soybean planting dates about 12 days. For both crops, but especially for corn, this was accompanied by a lengthening of the growth period. The period from corn planting to maturity was about 12 days longer around 2005 than it was around 1981. A large driver of this change was a 14% increase in the number of GDD needed for corn to progress through the reproductive period, probably reflecting an adoption of longer season cultivars. If these changes in cultivars had not occurred, yields around 2005 would have been 12.6 bu ac⁻¹ lower across the U.S. Corn Belt, erasing 26% of the yield increase from 1981 to 2005. These changes in crop phenology, together with a shortening of the time from maturity to harvest, have also modified the surface water and energy balance. Earlier planting has led to an increase in the latent heat flux and a decrease in the sensible heat flux in June, while a shorter time from maturity to harvest has meant an increase in net radiation in October.  相似文献   

Combining the simulation crop model AquaCrop with an economic model for the optimization of irrigation management at farm level   总被引：3，自引：0，他引：3  

Margarita García-Vila  Elías Fereres 《European Journal of Agronomy》2012,36(1):21-31

Water resources used in irrigated agriculture are increasingly scarce, particularly in many countries where irrigation has undergone recent expansion. To optimize the limited resources available, optimization models provide useful tools for technical and economic analyses. One of the key inputs of these models is the yield response to water which is often simulated with empirical water production functions. At present, dynamic crop simulation models, such as AquaCrop (Steduto et al., 2009) offer alternative predictions of crop responses to different irrigation strategies as inputs to economic optimization. A model at farm scale was developed and applied to an area in South-western Spain to assist farmers in pre-season decision making on cropping patterns and on irrigation strategies. Yield predictions were obtained from the AquaCrop model which was validated for four different crops. The model simulated the impact on farm income of: (a) irrigation water constraints; (b) variations in agricultural policies; (c) changes in product and water prices; and, (d) variations in the communication to farmers of the specific level of irrigation water allocation. The applications of the models to the study area showed that currently, the changes in cropping patterns induced by the agricultural policy will encourage water savings more than an increase in water prices. Under water restrictions, the best strategy combines planting of low water use crops in part of the area to release water to grow more profitable crops with greater water needs. The model predicted a strong negative impact on farm income of delaying a decision on the level of seasonal water allocation by the water authority, reaching up to 300 € ha⁻¹ in the case of the study area.  相似文献   

秸秆在肉牛饲养中的利用及其纤维表观消化率     

冯素飞  蒋高明  孔令杰 《山东农业科学》2009,(6):93-95

纤维素是世界上最丰富的可再生资源，将含纤维素丰富的秸秆处理作为饲料，对农业可持续发展和缓解秸秆焚烧压力有重要现实意义。本试验选择20头夏洛莱肉牛随机分成4组，测定肉牛对中性洗涤纤维和酸性洗涤纤维的表观消化率及体重。试验结果表明，不同处理组肉牛的采食及排泄中性洗涤纤维和酸性洗涤纤维均差异显著。微储鲜秸秆配合花生糠处理组中性洗涤纤维和酸性洗涤纤维的表观消化率均最高，分别为63．13％和45．35％，且肉牛的累计体重增加最大，7个月增加的体重平均为228kg。  相似文献   

Modeling morphological dynamics and color characteristics of rice panicle     

《European Journal of Agronomy》2014

This paper was to develop the models for predicting the dynamics of panicle geometric morphology, panicle and branch curves and panicle color, and to visualize rice panicle in three dimensions (3D). Based on three experiments with different rice (Oryza sativa L.) cultivars, the time-course data were collected on the panicle geometric morphology, (including the number of branches and spikelets, the lengths of panicle and branches, and the diameter of panicle axis), the spatial coordinates of panicle axis and branches, and the RGB (red, green and blue) values of panicle color in rice. The dynamics of rice panicle morphology, panicle and branch curves, and RGB values of panicle color with thermal time (TT) were then characterized and simulated. The derived models were further used to visualize rice panicle in 3D. The results indicated that some appropriate functions (quadratic, logistic, exponential and Gaussian) could be chosen to describe the dynamics of the panicle geometric morphology and the RGB values of panicle color with time (growing process) and space (distributions of panicle organs) during panicle development. Combining the above models with the topological structure of rice panicle, rice panicle was visualized with Microsoft.Net and OpenGL (a graphics library). Validation of the models with the independent data indicated that all relative root mean square errors (RRMSEs) between the measured and simulated values were below 20%. Comparison of virtual and real panicles at different development stages showed that the virtual rice panicles were quite similar to real panicles. Overall, the present study could effectively simulate the dynamic changes of 3D morphology and color characteristics of rice panicle, and would provide a key technological support for fulfilling visualization of the whole rice plant.  相似文献   

Estimation of past and recent carbon input by crops into agricultural soils of southeast Germany     

《European Journal of Agronomy》2014

In agricultural soils, the formation of soil organic matter largely depends on the carbon (C) input by crop residues and rhizodeposition, which is thus of decisive importance for the management and prediction of soil organic carbon (SOC) stocks in cropland and grassland. However, there is a remarkable lack of reliable, crop-specific C input data. We used a plant C allocation approach to estimate the C input of major crops and grassland into agricultural soils of Bavaria in southeast Germany. Historic and recent plant C allocation coefficients were estimated and C inputs were calculated for a 60-year period (1951–2010) using long-term agricultural statistics. The spatial distribution of C inputs within Bavaria was derived from county-specific statistical data. The results revealed increases of the C input by 107–139% for cereals, 173–188% for root, forage and leguminous crops and 34% for grassland in the last 60 years. This increase was related to linear yield increases until 1995 despite significant changes of plant C allocation. However, from 1995 onwards, crop yields and related C inputs stagnated, which allowed a robust estimation of recent crop-specific C input values. A total C input of 3.8–6.7 t ha⁻¹ yr⁻¹ was estimated for cereals, 5.2–6.3 t ha⁻¹ yr⁻¹ for root, forage and leguminous crops and 2.4 t ha⁻¹ yr⁻¹ for grassland. These amounts were partly higher compared to estimations in the literature. A generally high spatial variability of C inputs was detected within Bavaria with differences of up to 40% between adjacent counties. The results of this study could be used to optimize the C input of crop rotations and thus promote the formation of soil organic matter and C sequestration in agricultural soils on the basis of a soil carbon model. Moreover, recent estimations of C inputs could be used to model the future development of agricultural SOC stocks. A further stagnation of crop yields and the related C input under an ongoing temperature increase bears the risk of a future decrease of SOC stocks in cropland soils of Bavaria.  相似文献   

N2气调干燥气体状态参数计算方法     

朱文学  种翠娟  刘云宏  樊金玲  罗磊  吴建业 《农业机械学报》2013,44(11):174-179

用N2 代替部分空气进行闭路式气调热风干燥,可改善干燥品质,提高干燥速率。推导了不同N2 含量混合气流状态参数的计算公式,绘制了N2 惰性气体的湿焓图,并进行了不同N2 含量混合气流参数及传热传质系数的计算。结果表明,混合气流状态参数及传质系数均随N2 含量的增加而增加,传热系数随N2 含量的增加而减小。  相似文献