The need for efficient use of water resources has increased the importance of optimum soil water usage in agricultural systems. Soil temperature has been shown to be important in influencing the early development of many plant species. Many agricultural regions have suboptimal soil temperature regimes for plant growth, and some cultural practices have been shown to reduce near-surface soil temperatures. The seasonal influence of soil temperature on soil water extraction and aboveground and belowground plant growth under variable irrigation was investigated at the USU Greenville Farm in Logan, UT. Soil surface mulches and buried heat cables were used to modify soil temperature. A line-source sprinkler system provided a gradient of water application. During 1987 yields were mainly influenced by irrigation. During 1988 greater soil temperature differences resulted in significant plant growth and yield responses. Soil water depletion corresponded to soil temperature treatments during the early part of the growing seasons. Depth of maximum soil water depletion was about 20 cm deeper for warm treatments. Water uptake rates of earlier-maturing plants in warm treatments were reduced later in the season, so that cumulative seasonal soil water depletion was similar for all temperature treatments. Although depth of rooting was somewhat greater under high than low irrigation during 1988, low irrigation treatments depleted soil water to greater depth. There was no interactive response of plant growth and yield or of soil water depletion to soil temperature and irrigation treatments. Modifications were made to a computer simulation model of the soil-plant-atmosphere system in order to more mechanistically simulate plant water uptake and to include influences of soil temperature on seasonal rooting growth and soil water extraction. The model adequately simulated both the pattern and magnitude of soil temperature influences on soil water depletion, and conclusions drawn from model simulations agreed with field observations during 1987 and 1988.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-10-01T20:05:35Z No. of bitstreams: 1 SAULO FERREIRA LEITE - DISSERTAÇÃO (PPGRN) 2017.pdf: 2406592 bytes, checksum: 5572a5a89f2561da0262fd8ce71de0d7 (MD5) / Made available in DSpace on 2018-10-01T20:05:35Z (GMT). No. of bitstreams: 1 SAULO FERREIRA LEITE - DISSERTAÇÃO (PPGRN) 2017.pdf: 2406592 bytes, checksum: 5572a5a89f2561da0262fd8ce71de0d7 (MD5) Previous issue date: 2017 / Capes / O canteiro econômico é uma tecnologia social simples de fácil aplicação, que tem como proposta viabilizar a redução do consumo de água na produção de hortaliças, contribuindo para uma melhor gestão dos recursos naturais. O objetivo desta pesquisa foi realizar diagnóstico socioeconômico e ambiental e avaliar de forma comparativa o crescimento e desenvolvimento da alface orgânica cultivada em canteiro econômico e convencional. A pesquisa realizou-se em duas etapas: a primeira etapa efetuou-se diagnóstico socioeconômico e ambiental no assentamento Oziel Pereira, comunidade agrovila do Cajá, Remígio, PB, entre março e maio de 2016, aplicou-se questionário estruturado com 30 famílias agricultoras em nível de núcleo familiar, a analise das unidades foi a partir do estudo analítico de códigos. Na segunda etapa avaliou-se a cultura da alface orgânica cultivada em canteiro econômico e convencional, o experimento foi conduzido em campo aberto, na comunidade, entre agosto e novembro de 2016. O delineamento experimental foi casualizado, com três repetições, pelo arranjo fatorial 2x2x2, duas águas, com e sem sombrite e manejo “econômico e convencional”. Foram avaliados: número de folha; massa fresca da folha; altura de planta; taxa de crescimento absoluto e relativo; consumo de água; eficiência do uso da água e condutividade elétrica do extrato da solução do solo. A irrigação foi determinada pelo método das pesagens. Na primeira etapa, os índices: 91,25%, 18,25% e 33,62%, de deterioração do diagnóstico econômico, ambiental e social, respectivamente, colaboraram para a degradação socioeconômica 38%, sendo o fator econômico o que mais contribuiu para esse resultado. As variáveis demográfica e alimentar foram as que provocaram a deterioração no fator social. Na segunda etapa, o uso do sombrite foi tão produtivo quanto ao cultivo em céu aberto. O consumo de água foi mais eficiente no canteiro econômico. A eficiência do uso da água diminuiu com o acréscimo da lâmina de irrigação e o uso da água salobra deve ser manejado com racionalidade no canteiro econômico. A degradação de 91,25% fator econômico, provavelmente estar relacionada ao longo período de estiagem dos últimos seis anos e a falta de politicas públicas para o semiárido. A participação das famílias junto às praticas agroecológicas contribuiu para o melhor resultado do diagnostico ambiental. Com esses resultados pode-se concluir que o canteiro econômico é viável como politica pública para mitigar os efeitos da estiagem e garantir segurança alimentar e nutricional; o uso do sombrite é indispensável no semiárido. / The economic bed is a simple social technology of easy application, whose purpose is to enable the reduction of water consumption in the production of vegetables, contributing to better management of natural resources. The objective of this research was to perform socioeconomic and environmental diagnosis and to evaluate in a comparative way the growth and development of organic lettuce grown in an economical and conventional field. The research was carried out in two stages: the first stage was a socioeconomic and environmental diagnosis in the settlement Oziel Pereira, community agrovila do Cajá, Remígio, PB, between March and May 2016, a structured questionnaire was applied with 30 families farmers in At the family nucleus level, the analysis of the units was based on the analytical study of codes. The second stage evaluated the cultivation of organic lettuce cultivated in an economical and conventional field, the experiment was conducted in the open field, in the community, between August and November 2016. The experimental design was randomized, with three replications, by factorial arrangement 2x2x2 , two waters, with and without sombrite and "economic and conventional" management. The following were evaluated: leaf number; fresh leaf mass; plant height; absolute and relative growth rate; Water consumption; efficiency of water use and electrical conductivity of soil solution extract. Irrigation was determined by the weighing method. In the first stage, the indices: 91.25%, 18.25% and 33.62%, of deterioration of the economic, environmental and social diagnosis, respectively, contributed to the socioeconomic degradation 38%, being the economic factor that contributed the most for this result. The demographic and food variables were those that caused the deterioration in the social factor. In the second stage, the use of sombrite was as productive as open-air cultivation. Water consumption was more efficient at the economic site. The efficiency of water use has decreased with the addition of the irrigation blade and the use of brackish water must be handled with rationality in the economic field. The degradation of 91.25% economic factor, probably related to the long drought period of the last six years and the lack of public policies for the semi-arid. The participation of the families in the agroecological practices contributed to the best result of the environmental diagnosis. With these results it can be concluded that the economic scenario is viable as a public policy to mitigate the effects of drought and to guarantee food and nutritional security; the use of sombrite is indispensable in the semiarid.