Browsing by Subject "Agronomy"

Now showing 1 - 3 of 3
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    Evaluation of weed control and economic benefit of a light-activated sprayer in cotton
    (Texas Tech University, 2003-12) Peters, D Alan
    Field experiments were conducted from 2000-2002 to evaluate weed control and economic performance of a light-activated sprayer (LAS) m cotton. Herbicide treatments were applied with a broadcast sprayer, a conventional hooded sprayer (OS) or LAS. Treatments included prometryn at 1.34 kg ai/ha preemergence followed by (fb) cultivation as needed (ASN); glyphosate at 1.12 kg ai/ha applied postemergence over-the-top (POT) at the four-leaf growth stage of cotton fb glyphosate at 1.12 kg ai/ha applied with CS ASN; glyphosate at 1.12 kg ai/ha applied POT at the four-leaf stage fb glyphosate at 1.12 kg ai/ha applied with LAS ASN; and glyphosate at 1.12 kg ai/ha applied in a 36-cm band over the row at the four-leaf stage plus glyphosate at 1.12 kg ai/ha applied with LAS fb glyphosate at 1.12 kg ai/ha applied with LAS ASN. Weed control was evaluated 14 and 28 days after the last treatment was applied (DAT). Herbicide savings were calculated by measuring the amount of spray solution in the tank before and after treating each LAS-treated plot. Economic analysis included total specified expenses and fixed expenses (irrigation maintenance and hooded sprayer cost); and returns above total specified expenses, derived from the sale of cotton lint and seed. The light-activated sprayer generally controlled weeds similar to the conventional sprayer and better than cultivation, regardless of whether a band or broadcast application of glyphosate was made at the 4-leaf growth stage of cotton. The additional cost of LAS was offset by reductions in herbicide use; however, net returns were not increased when compared to a conventional sprayer. Additional research was conducted to investigate the potential for plant species differentiation by spectral reflectance. Reflectance was measured using sixteen wavelengths for two crops and four weed species at two growth stages. When small plants were measured, wavelengths 600, 630, 650, 670, 700, 1600, and 1700 nm revealed no similarities between species. At wavelengths 450,470, 630, 650, and 670 nm, data revealed that reflectance of large cotton plants was different from every weed species evaluated. Wavelengths were identified that have potential for use in species differentiation by spectral reflectance measurements.
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    Genetic variation of heat tolerance and correlation with other agronomic traits in a maize (Zea mays L.) recombinant inbred line population
    (Texas Tech University, 2003-08) Bai, Jiangping
    Heat stress is a critical environmental factor that affects agricultural production in the southwest of the United States, especially in West Texas. Heat stress can reduce plant height, kill the leaf tissues, cause abortion of pollen and kernel, and affect the cell activities. The objectives of this study were to determine the genetic variation of leaf firing, chlorophyll fluorescence, plant height, ear height, leaves above ear, number of tassel branches, days to flowering and yield per plant in a recombinant inbred line population, and to estimate the heritability of those traits. A total of 179 maize recombinant inbred lines from B76 x B106 were evaluated at Pecos, TX, in 2001, at Texas Tech University (TTU) experimental farm in 2002, and at TAMU Lubbock center in 2001 and 2002. Significant variation in leaf firing, chlorophyll fluorescence and other agronomic traits were found among the RILs. In the population, leaf firing ranged from 0% to 92.9% in Lubbock-TAMU 2001 test, 0% to 100% in Pecos 2001 test, 0% to 67.9% in Lubbock-TAMU 2002 test, and 0% to 100% in Lubbock-TTU 2002 test. The average of chlorophyll fluorescence of the RILs ranged from 0 to 0.79 (2001 Lubbock-TAMU), 0.14 to 0.78 (2002 Lubbock-TAMU), and 0.02 to 0.76 (2002 Lubbock-TTU). Leaf finng,chlorophyll fluorescence and other agronomic traits also showed transgressive segregation in the population in each environment. Only plant height, ear height, number of tassel branches (2001 and 2002 Lubbock-TAMU), and leaves above ear (2002 Lubbock-TAMU) showed the normality distribution. Under heat stress, yield per plant was negatively correlated with percent leaf finng and days to flowering and positively correlated with chlorophyll fluorescence and number of tassel branches. Percent leaf firing was negatively correlated vMth chlorophyll fluorescence. Number of tassel branches was positively correlated with plant height and ear height. Leaf firing and chlorophyll fluorescence did not show strong correlation with plant height, ear height, number of tasel branches, and leaves above ear. The broad-sense heritability for leaf firing and chlorophyll fluorescence was 0.32 and 0.28 on the plot basis, respectively, and 0.85 and 0.77 on the mean basis. From their low heritability based on plot, high heritability based on means, and large genotype x environment interactions, we believe that the heat tolerance in maize is inherited quantitatively, and effective selection for heat tolerance requires evaluation genotypes in replicated trails in multiple environments.
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    Nitrogen and phosphorus nutrition for semi-dwarf castor (Ricinus communis L.) production in West Texas
    (2012-08) Wallace, Sean M.; Trostle, Calvin S.; Auld, Dick L.; Wheeler, Terry A.
    In general technical nitrogen and phosphorus requirements have not been established for castor in the United States. Brazil and India have each shown nutrient requirements for castor although the climate, soil types, cultivars, and cultivation techniques are vastly different than what would be used regionally in the United States. Our objective is to measure yield response to nitrogen fertilization on irrigated castor in West Texas. Field tests were conducted 2010-2011 at Lubbock, TX (Texas Tech University Quaker Research Farm, and Texas AgriLife Extension and Research Farm), and 2010 at Pecos, TX (Texas AgriLife Research Farm), using an RCDB layout with five replication of five treatments (0-40-80-120-160 lbs/A of N added in the form of UAN). Spring soil samples were collected from each plot (0-6”, 6-12”, 12-24”, 24-36”, and if possible 36-48”, 48-60” depths) and analyzed for nitrate and ammonium nitrogen, and additionally Melich III phosphorus for phosphorus test sites. The 2011 drought reduced the yields enough to likely overshadow possible significant differences. The 2010 TTU Quaker Research Farm Site showed significant increases in yield from the 80 and 120 lbs/A N vs. the 0 lbs/A N treatment (P = 0.05), with soil test to the 36” depth showing an accumulation that averaged around 45 lbs/A of nitrate nitrogen. The 2010 AgriLife Lubbock Research Farm site soil test results show large accumulations of soil nitrate nitrogen to the depth of 36” averaging near 150 lbs/A, with no significance differences between N treatments. The 2010 AgriLife Pecos Research Farm site soil test results also showed large accumulations of soil nitrate nitrogen to the depth of 36” averaging near 250 lbs/A. Yields for this site were low and differences were not meaningful, significant differences between treatments were found between the 0 and 40 lbs/A treatment vs. the 160 lbs/A treatment (P = 0.05). The sites with low levels of rainfall and irrigation showed N treatments ineffective at increasing yield. Test sites with higher levels of rainfall and irrigation show the treatments of 80-120 lbs/A of nitrogen to significantly increase the yield. High subsoil nitrate nitrogen levels masked any yield response to nitrogen fertilizers. Overall, the fields appear to have adequate P levels for most. Unlike typical recommended 0-6” soil tests for P, moderate levels of P were also measured at 6-12” for Quaker 2010 & Quaker 2011, and Lubbock 2011. For the Quaker 2010 & Quaker 2011, and Lubbock 2011 sites when subsoil P at 6-12” is added to 0-6” then the combined soil P became 25 to 39 ppm, or in the lower range of moderate P to a higher moderate range soil P. Only one test site showed any positive response to P fertilization Quaker 2010 testing 19 ppm P 0-6” or combining with the 6-12” sample of 10 ppm P totaling 29 ppm P. The recommendation for this 29 ppm P would be the addition of 20-40 lbs P2O5 fertilizer.