No‐tillage systems for cotton (Gossypium hirsutum L.) production on sloping, upland sites have not been widely adopted in the Mid‐South of the USA, even though conventional cotton production creates a serious erosion hazard. A field study was established following sod on a site with loess soils to evaluate tillage system effect on cotton yield and earliness. The sod was tilled prior to establishment of treatments, which included conventional (chisel, disk, bed, cultivate), ridge till (remove ridge tops at planting, cultivate postemergence to rebuild ridges), no‐tillage [wheat (Triticum aestivum L.) cover seeded following cotton harvest, killed prior to planting], and minimum tillage (one pass with a mulch finisher prior to planting, cultivate postemergence). During the first year of the study, no‐tillage cotton yields were lower and maturity delayed compared with conventional tillage. During Years 3 to 5, no‐tillage crop yields were 18 to 42% greater and crop maturity was 6 to 10 d earlier than conventional tillage. Minimum tillage yields were similar to conventional tillage while ridge tillage was lower in two of the last 3 yr of the study. Results of this study indicate viable no‐tillage production systems for cotton can be developed for highly erosive loess soils in the Mid‐South.
Yield component analysis of 9 Vaccinium corymbosum L. blueberry cultivars indicated that yield was more strongly determined by canes per bush and berries per cane than by berry weight. High numbers of berries per cane were associated with low berry weights in all cultivars. Component interactions ranged from slightly additive in ‘Bluecrop’ and ‘Spartan’ to highly compensatory in ‘Rubel’ and ‘Berkeley’. The consideration of component interactions in cultivar trials may enhance the accuracy in identification of desirable genotypes.
Inbreeding coefficients were calculated for the 63 cultivars of blueberry (Vaccinium corymbosum L.) released by public agencies in the United States. A steady increase in coefficients was noted from the period of 1910−1920 (F=0.00) to 1960−1970 (F=0.13). ‘Lateblue’ and ‘Flordablue’ had the highest coefficient of 0.25. Most of the genes in the cultivars came from the wild selections ‘Brooks’, ‘Sooy’ and ‘Rubel’.
Sixteen cultivars of blueberry (Vaccinium corymbosum L.) were field screened for resistance to the blueberry aphid Illinoia pepperi (McGillivary), the vector of blueberry shoestring virus. Significant differences were observed with ‘Bluejay’, ‘Northland’, ‘Bluetta’ and ‘Bluehaven’ supporting the lowest numbers, while ‘Spartan’, ‘Darrow’, ‘Lateblue’, ‘Coville’ and ‘Jersey’ carried the highest numbers. There was no significant correlation between aphid number and new shoot number, percentage of shoots with new growth, length of new growth, leaf length or leaf width. Half of the aphids were found in the lower 1/3 of the bushes.
Differences were observed both within and between strawberry cultivars in the relative importance of yield components. Most cultivars had high coefficients among yield, crown density at harvest, and fruit number/crown, but there was variation among cultivars in the coefficients between yield and fruit weight.
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