玉米保护地栽培技术

阐述了玉米保护地立体栽培技术,该项技术是当前农业生产投资少、见效快、受益大的新举措,有可行性、重演性、可操作性,符合推广法要求,前景广阔。本文介绍了玉米保护地立体栽培的由来、技术模式、产量效益等。     

The Term Structure of Implied Forward Volatility: Recovery and Informational Content in the Corn Options Market

Using a flexible method, we develop the term structure of volatility implied by corn futures options with differing maturities, and evaluate its ability to predict subsequent realized price volatility. The implied forward volatilities anticipate realized volatility well. For the nearby interval, the implied forward volatilities provide unbiased forecasts, and are superior to forecasts based on historical volatilities. For more distant intervals, early-year options predict the direction and magnitude of future volatility changes about as well as a three-year moving average and better than a naïve forecast. However, later-year options display less forecast power in part due to reduced trading activity.     

Evaluation of USDA Interval Forecasts of Corn and Soybean Prices

USDA World Agricultural Supply and Demand Estimates (WASDE) price forecasts are published as an interval, but are typically analyzed as point estimates. Thus, all information about uncertainty imbedded in the forecast is ignored. The purpose of this article is to evaluate the accuracy of WASDE corn and soybean price forecasts using methodology suitable for testing judgmental interval forecasts. Accuracy tests suggest that WASDE forecasts are not calibrated at the 95% confidence level for both commodities and generally not calibrated for corn, but calibrated for soybeans, at the implied confidence level elicited from the survey of forecast providers.     

红景天黑玉米复合功能饮料的研制

用乙醇提取法从红景天根茎中提取分离得到有效成分红景天甙提取物,并与黑糯玉米原料配伍,制成风味独特的红景天黑玉米复合功能饮料。经正交设计试验得到优选的工艺参数和配方,即红景天甙粗品用量0.05%,玉米提取液用量25%,蔗糖用量9%,柠檬酸用量0.20%。     

Nonlinear Dynamics and Structural Change in the U.S. Hog–Corn Cycle: A Time-Varying STAR Approach

The linearity of the U.S. hog–corn cycle has been questioned by Chavas and Holt (1991) . Even so, attempts have not been made to model the potential nonlinear dynamics in the hog–corn cycle by using regime-switching models. One popular alternative is Teräsvirta's smooth transition autoregressive (STAR) model, which assumes regime switching is endogenous and potentially smooth. In this article, we examine monthly data for the U.S. hog–corn cycle, 1910–2004. A member of the STAR family, the time-varying STAR, is fitted to the data and its properties examined. We find evidence of nonlinearity, regime-dependent behavior, and time-varying parameter change.     

A Methodology for Farm-Level Economic Analysis of Soil Erosion Effects Under Alternative Crop Rotational Systems in Ontario

Multiperiod linear programming techniques are used to evaluate comparative profitabilities and soil erosion rates for corn grown monoculturally and in rotation with a) soybeans, b) soybeans and oats, c) barley, and d) alfalfa on moderately sloping land with medium loam soils in southern Ontario. Attention is focussed on the case of a highly leveraged recent entrant to farming with heavy debt servicing needs and potential cash flow constraints. Monocultural corn was found to be more profitable than any of the rotational systems, with corn-soybeans rotations the next most profitable and corn-barley rotations the least profitable. Corn-soybeans caused the highest soil erosion, followed by continuous corn, with corn-alfalfa rotations causing the least. Les techniques de programmation linéaire multipériode sont utilisées pour évaluer et comparer les niveaux de profit et les taux d' érosion de sols agricoles moyennement argileux pour des systèmes de production de grandees cultyres localiées dans le sud de l' ontario et produisant, soit du mais en régime de monoculture, soit du mais en rotation avec: a) du soja, b) soja et avoine, c) orge. et d) de la luzerne plantée sur des terrains à pentes modérées. L' analyse developpée dans cet article met l' accent sur des agriculteurs récemment installés, disposant de beaucoup d' actifs, mais également, ayant des besoins énormes d' emprunts et, par conséquent, soumis à des contraintes potentielles sur leurs cash-flows. Les résultats obtenus montrent que le système de production, mais-monoculture, est le plus viable de tous les systèmes etudies. Parmi les systemes de production reposant sur une rotation culturale, il s' avère que celui combinant maïs et soja vienne en seconde position, tandis que un régime cultural fondé sur une rotation maïs et orge donne les pires resultats. Pour ce qui concerne des taux d' erosion des sols, la rotation maïs-soja cause les plus gros dommages. ensuite suivie par le système de production, maïs-monoculture. Finalement, les taux d' erosion les plus faibles ont été obtenus pour la rotation culturale, maïs-luzerne.     

2020年新收获玉米质量监测分析

目的:为及时了解2020年辽宁地区玉米的质量状况,为中央储备玉米收购提供科学依据,对新收获玉米质量情况进行监测.方法:本次监测采取田间取样为主、庭院取样为辅的方法进行,本着有代表性和重点突出的原则选择3～5个乡,每乡选择3～5个自然村,每个村选择不少于5个有代表性的农户.将所采集的村级样品混合均匀,形成一份样品.共采集...     

清代中晚期山地种植玉米引发的水土流失及其遏止措施

清代中晚期，我国渭河至黄河下游一线以南、青藏高原以东范围内，人们广泛开垦山地，种植玉米，许多地方出现了“遍山漫谷皆包谷”的景象。大面积的山地开垦和玉米种植，破坏了原有的自然植被，引发严重的水土流失。在不同地区，官方和民间对开山种玉米的利弊有不同认识。在四川、湖北、湖南等省，政府对开辟荒山种植玉米的行为基本上是听之任之；但在浙江、皖南和陕南等地，政府和民间曾采取多种积极措施，遏止山地种植玉米引发的水土流失，并取得了一定成效。