63,615 research outputs found
Adapting weed management in rice to changing climates
No full textThis paper provides some of the scientific background on how projected environmental conditions could affect weeds and weed management in rice in Africa. Elevated CO2 levels may have positive effects on rice competitiveness with C4 weeds, but these are generally outnumbered by C3 species in weed populations of rice in Africa. Moreover, higher temperatures and drought will favor C4 over C3 plants. Increased CO2 levels may also improve tolerance of rice against parasitic weeds, while invasiveness of such species may be stimulated by soil degradation and more frequent droughts or floods. Elevated CO2 may increase belowground relative to aboveground growth, in particular of perennial (C3) species, rendering mechanical control less effective or even counterproductive. Increased CO2 levels, rainfall and temperature may also reduce the effectiveness of chemical control. The implementation of climate change adaptation technologies, such as drought-tolerant germplasm and water-saving irrigation regimes, will also have consequences for rice–weed competition. Rainfed production systems are hypothesized to be most vulnerable to direct effects of climate change (e.g. changes in rainfall patterns) and are likely to face increased competition from C4 and parasitic weeds. Bioticstress- tolerant rice cultivars to be developed for these systems should encompass weed competitiveness and parasitic-weed resistance. In irrigated systems, indirect effects will be more important and weed management strategies should be diversified to lessen dependency on herbicides and mechanical control, and be targeted to perennial rhizotomous (C3) weeds. Water-saving production methods that replace the weed-suppressive flood water layer by intermittent or continuous periods of aerobic conditions, necessitate additional weed management strategies to address the inherent increases in weed competition
Letter from J. R. Eakin to Arthur G. Ringland
No full textLetter (copy) from J. R. Eakin to Arthur C. Ringland about the alignment of 40 acres near the Buggeln ranch
Letter from Arno B. Cammerer to J. R. Eakin
No full textLetter from Arno B. Cammerer to J. R. Eakin describing the procedure for purchasing Bright Angel Trail
Letter from J. R. Eakin to Carl Hayden
No full textLetter from J. R. Eakin to Carl T. Hayden concerning access to Rowe Well and the canyon
Letter from J. R. Eakin to Stephen Mather
No full textLetter from J. R. Eakin to Stephen T. Mather about expenses and reconstruction of the Kaibab Trail
Letter from Carl Hayden to J. R. Eakin
No full textLetter from Carl T. Hayden to J. R. Eakin regarding changes to the Grand Canyon National Park boundaries and the purchase of lands from William Randolph Hearst
Letter from J. R. Eakin to Stephen Mather
No full textLetter from J. R. Eaking to the National Park Service director about changes to the Grand Canyon National Park boundaries, and access to water near the Buggeln property on Desert View road
[Letter from J. R. Roberts to Sister, November 24, 1878]
No full textLetter from J. R. Roberts to sister. J. R. thanked his sister for gifts that were sent and went on to update her on what was happening in their families' lives. The letter ended with a mention that people were searching for land claims in the area and the author wanted their mother to not worry about them
Letter from J. R. Eakin, Grand Canyon National Park to Carl Hayden
No full textLetter from J. R. Eakin to Carl Hayden regarding the sale of Bass properties to the Santa Fe Railroad Company
Letter from J. R. Eakin, Grand Canyon National Park to Carl Hayden
No full textLetter from J. R. Eakin to Carl Hayden justifying the value of his land at twenty-five thousand dollars
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