نتایج جستجو برای: modern crop varieties

تعداد نتایج: 290957  

2009
Lars P. Kiær Ib M. Skovgaard Hanne Østergård

Plant ecology theory predicts that growing seed mixtures of varieties (variety mixtures) may increase grain yields compared to the average of component varieties in pure stands. Published results from field trials of cereal variety mixtures demonstrate, however, both positive and negative effects on grain yield. To investigate the prevalence and preconditions for positive mixing effects, report...

2008
Lu-xiang Liu Hui-jun Guo Linshu Zhao Jiayu Gu Shirong Zhao

Aerospace provides a special environment with strong cosmic radiation, microgravity, weak geomagnetic field and supervacuum, etc., which might affect plant growth and development as well as induce genetic changes of crop seeds. Since 1987, China has been conducting experiments of space mutagenesis for crop improvement by using recoverable satellites and Shenzhou spacecrafts. Shijian-8, the firs...

2016
Qingfeng Meng Xinping Chen David B. Lobell Zhenling Cui Yi Zhang Haishun Yang Fusuo Zhang

Climate change can reduce crop yields and thereby threaten food security. The current measures used to adapt to climate change involve avoiding crops yield decrease, however, the limitations of such measures due to water and other resources scarcity have not been well understood. Here, we quantify how the sensitivity of maize to water availability has increased because of the shift toward longe...

Journal: :Journal of experimental botany 2002
M H Jeuffroy B Ney A Ourry

Today farmers have several constraints to take into account in managing their crops: (i) competitiveness: productivity must be maintained or increased whereas inputs must be decreased, (ii) the environmental consequences of cultural practices: pesticide and fertilizer use must be decreased, and (iii) product quality must be improved and nitrogen nutrition is an important factor in harvest quali...

ژورنال: علوم آب و خاک 2008
صبوری, صمد , عسکری اصلی ارده, عزت‌اله , علیزاده, محمدرضا ,

A considerable portion of threshing losses and waste of rice takes place in threshing stage. One of the effective factors in threshing losses and waste of threshing units, threshers and harvesting machines, is the drum speed. In this research, effects of three factors including drum speed (five levels), crop moisture content (two levels) and rice common varieties (four varieties) on threshing l...

Journal: :Environmental entomology 2014
Faye E Benjamin Rachael Winfree

Modern agriculture relies on domesticated pollinators such as the honey bee (Apis mellifera L.), and to a lesser extent on native pollinators, for the production of animal-pollinated crops. There is growing concern that pollinator availability may not keep pace with increasing agricultural production. However, whether crop production is in fact pollen-limited at the field scale has rarely been ...

2017
Tigist Mekonnen

This paper provides empirical evidence regarding the impact of agricultural technologies on smallholders’ output market participation. The analysis is based on Farmer Innovation Fund impact evaluation survey collected by the World Bank in 2010-2012 covering 2,675 households in Ethiopia. Endogenous treatment effect and sample selection models are employed to account for the self-selection bias i...

2002
Matthew D. Kleinhenz

Declines in cabbage (Brassica oleracea var. capitata) crop quality may result from delaying harvest to allow for greater total yield. An accurate, reliable, rapid and inexpensive method to estimate yield before harvest not requiring direct weight measurements would assist cabbage growers and handlers in harvest scheduling. Results from 3 years of study during which a tool to predict cabbage yie...

Journal: :American journal of botany 2003
Kenneth Birnbaum Rob Desalle Charles M Peters Philip N Benfey

Maintaining crop diversity on farms where cultivars can evolve is a conservation goal, but few tools are available to assess the long-term maintenance of genetic diversity on farms. One important issue for on-farm conservation is gene flow from crops with a narrow genetic base into related populations that are genetically diverse. In a case study of avocado (Persea americana var. americana) in ...

2003
M. Faye J. L. DeBoer A. Sène M. Ndiaye

Since the 1980s cowpea has become an alternative cash crop in northern Senegal. However, in 1997, surveys showed that farmers often sold their crop at unprofi table prices. The hypothesis was that farmers could improve selling prices if they produced cowpea with the characteristics demanded by consumers. To identify those characteristics, data were collected in six markets from January 1998 to ...

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