Optimum cotton (Gossypium hirsutum L.) yield with good fiber quality requires healthy vigorous plants throughout the season. Recently, verticillinm wilt (Verticilllum dahllae Kleb.) and K deficiency symptoms occurred during August and September in cotton grown on sandy loam soils of the Mississippi Delta. Symptoms developed earlier and faster in some caitivars compared with others. In a field study, applications of K and pesticides on verticillium wilt‐K deftciency symptoms, yield and fiber quality of ‘DES 119’ and ‘Stoneville 825’ cottons were evaluated. Broadcast application and topsoil incorporation of 112 kg K ha‐1 yr‐1 reduced verticillium wilt‐K deficiency symptoms from 12 to 7%, averaged across both cultivars, but did not affect lint yield. The root‐gall [caused by Meloidogyne incognita (Kofoid & White) Chitwood] index was reduced from 2.7 to 2.5 and from 2.7 to 2.4 by K and aldicarb‐PCNB‐ETMT [5% 2‐methyl‐2‐(methylthio)propionaidehyde‐O‐(methylcarbamoyl)oxime + 10% pentachloronitrobenzene + 2.5% 5‐ethoxy‐3‐(trichloromethyi)‐l,2,4‐thiodiazole; 0.56 + 1.12 + 0.28 kg a.i. ha‐1], respectively. Fiber strength (kN m kg‐1) was increased from 20.4 to 20.9 by K and micronaire reading was increased from 3.99 to 4.13 by aldicarb treatment. Yield, fiber quality, verticillinm wilt‐K deftciency symptoms, and root‐gall index differed between euitivars. In soil infested with V. dahliae and M. incognita, K could be used to reduce verticillium wilt‐K deficiency symptoms and root‐gall index and to increase fiber strength of cotton. Aldicarb also can be used to reduce root‐gall index. Knowing the reaction of cotton cultivars to K and to pesticides should help cotton breeders develop better adapted cultivars.

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Rapid germination and emergence and vigorous seedling growth enhance the opportunities for profitable production of cotton (Gossypium hirsutum L.). Within seed lot, the heavier, more dense seed are most likely to exhibit these traits. In 1976, acid‐delinted, gravity‐graded seed of ‘Paymaster 909’ and ‘Tamcot SP37’ were separated into four density classes by a liquid separation process. These classes were: D1 = very low density (floaters); D2 = low density; D3 = medium density; and D4 = high density. Seed with cracked coats were included in the D4 class. Commercially gravity‐graded (DG) seed of each cultivar were used as standards. All samples were treated with carboxin‐captafol {(5,6‐dihydro‐2‐methyl‐1, 4‐oxathiin‐ 3‐carboxanilide plus cis‐N‐[(l,l,2,2‐tetrachloroethyl) thio]‐4‐cyclohexene‐l,2‐dicarboximide)} 2‐2 F SP (2 lbs. of each fungicide as aflowable seed protectant) at g/kg of seed. Enough seeds of each class were obtained to conduct tests for 2 years. The Paymaster 909 select seed were representative of the type commonly planted by area farmers. Tamcot SP37 seed were obtained from a planting of registered seed that failed to mature properly and consequently failed to meet germination reqmrements for certification in Texas. Seed index, germination, and stand were highest and the prevalence of Verticillinm wilt (caused by Verticillium dahliae Kleb.) was lowest in plants from D3 seed, but plants from D2 seed performed almost as well. The poorest overall performance was shown by plants from D1 seed, whereas the performance of plants from D4 seed lots equaled or slightly exceeded that of plants from DG seed. The liquid seed‐separation process may enable seed proeessors to isolate seed for significantly improved germination, seedling survival, and lint yield, and reduced prevalence of Verticillium wilt. The liquid separation process may be used in breeding and seed‐increase programs to select high‐quallty planting seed for performance evaluations. The process also may be used to isolate seed of acceptable quality for planting from seed that fail to meet quality standards after commercial gravity grading. Seed index may be used to select density classes for planting seed.

The effects of row and plant spacings on percent Verticillium wilt (Verticillium albo‐atrum Reinke and Berth.) in ‘Gregg 35,’ a wilt‐susceptible cotton (Gossypium hirsutum L.) adapted to a wide range of row and plant spacings, were studied in single‐ and double‐row planting patterns. Percent wilt was decreased slightly in double‐row and significantly in single‐row patterns by close row spacings. In both planting patterns percent wilt decreased as plant populations (seeding rates) increased from low to medium levels, but percent wilt remained constant or decreased slightly at higher plant populations. The interaction of row widths ✕ seeding rates was significant only for the single‐row patterns.

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