Precision management of cotton production can increase profitability by decreasing inputs. The overall objective of this project is to improve cotton production by minimizing seeding rates while still maximizing yields and lint quality in water-limited soils. The research for this study was conducted at the Texas AgriLife Research IMPACT Center located in the Brazos River floodplain. In 2008 and 2009, 27 measurement locations were selected in production-sized center-pivot irrigated fields and planted in cotton variety Deltapine 164 roundup ready flex / bollgard II. Sites were selected based on soil apparent electrical conductivity (ECa) values, in a low, medium, and high ECa zones. Three seeding rates (74,100; 98,800; and 123,500 seeds ha-1) were established in each of the three ECa zones with three replications. In 2009, an additional seeding rate was added at 49,400 seeds ha-1. At each measurement location, soil texture, soil moisture (weekly), lint quantity and quality (High Volume Instrument) were measured. An additional replication for each ECa zone and seeding rate was selected for lint quantity and quality (HVI) measurements. Results indicated that cotton lint yield increased as ECa values, clay content, and water holding capacity of the soil increased. The seeding rates did not consistently affect cotton lint yield or quality. Seeding rates of 74,100 and 49,400 seeds ha-1 in a low and medium ECa zone for IMPACT-08 and -09 yielded more lint (300 kg ha-1), respectively. HVI lint quality parameters, such as, micronaire, fiber length, strength, uniformity, and elongation were significantly better in ECa zone 3. While the seeding rates did not affect the amount of soil water used throughout the season, lint yield variations between ECa zones can be explained by the rate at which soil water was used. Lower rates at which soil water was used within ECa zone 3 resulted in higher lint yields when compared to ECa zones 1 and 2, which used soil water faster and at greater depths. The findings suggest that irrigation applied to the low ECa zone was not sufficient to meet the plants demand, while in a high ECa zone, irrigation could have been reduced, resulting in cost savings through reduced inputs.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-11-30T09:09:36Z No. of bitstreams: 2 Dissertação - Antônio Marcelino da Silva Filho - 2015.pdf: 2204549 bytes, checksum: 2f0941c7970eff84c86b64f4fd261cb6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-11-30T09:11:40Z (GMT) No. of bitstreams: 2 Dissertação - Antônio Marcelino da Silva Filho - 2015.pdf: 2204549 bytes, checksum: 2f0941c7970eff84c86b64f4fd261cb6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-11-30T09:11:40Z (GMT). No. of bitstreams: 2 Dissertação - Antônio Marcelino da Silva Filho - 2015.pdf: 2204549 bytes, checksum: 2f0941c7970eff84c86b64f4fd261cb6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-12-19 / This work presents the study of the relationship between soil apparent electrical resistivity ρa and the moisture content, clay content and soil compaction, for use of the ρa as a mapping tool of spatial soil variability. The values of apparent electrical resistivity are obtained by geoelectrical prospecting methods that detect the effects produced by the flow of electrical current in the soil. It is used the Wenner array and the technique of Lateral Profiling for data collection. It was held measures of ρa in different soil types, varying moisture content gradually while maintaining a constant compaction, and then varying the compaction and relating it to a constant humidity. To the study of spatial variability, it was chose two areas that would enable the change of moisture and compaction content, in order to verify the measurement capacity of ρa as methodology of identification of change in soil dynamics. The results obtained are presented and discussed. / Este trabalho apresenta o estudo das rela¸c˜oes entre a resistividade el´etrica aparente do solo ρa e o teor de umidade, teor de argila e compacta¸c˜ao do solo, para utiliza¸c˜ao de ρa como ferramenta de mapeamento da variabilidade espacial do solo. Os valores da resistividade el´etrica aparente s˜ao obtidos atrav´es de m´etodos de prospec¸c˜ao geoel´etricos que detectam os efeitos produzidos pelo fluxo de corrente el´etrica no solo. Utilizam-se o arranjo de Wenner e a t´ecnica do Caminhamento El´etrico para coleta dos dados. Realizaram-se medidas de ρa em diferentes tipos de solo, variando-se gradualmente o teor de umidade, mantendo-se constante a compacta¸c˜ao, e posteriormente variando a compacta¸c˜ao em fun¸c˜ao de valor constante de umidade. Para o estudo da variabilidade espacial, escolheram-se duas ´areas que possibilitassem a altera¸c˜ao dos teores de umidade e compacta¸c˜ao, a fim de verificar a capacidade da medi¸c˜ao de ρa como metodologia de identifica¸c˜ao de altera¸c˜oes na dinˆamica do solo. Os resultados obtidos s˜ao apresentados e discutidos.