Canopy photosynthesis,stomatal conductance and yield ofSolanum tuberosum grown in a warm climate

Selected potato (Solanum tuberosum L.) genotypes were grown in the field from May to September during 1984 and 1985, to study their growth and gas exchange responses in a warm climate. The parameters measured were leaf area index (LAI), canopy photosynthesis on ground area basis (CPn-Ga), stomatal conductance, dry matter partitioning and yield. The LAI ranged from 1.40 for Dakchip to 6.60 for Pungo during August 1984. The LAI also differed significantly among the potato genotypes for the three samplings during 1985. Atlantic, Chipbelle and DTO-33 showed no decline in their LAI up to 73 days after planting (DAP), indicating a better heat-stress tolerance response than the other genotypes. During both years, CPn-Ga differed significantly among the genotypes and Pungo had higher CPn-Ga than all the other genotypes. Mean CPn-Ga rates were 1.72 and 4.34 g CO₂ m^?2hr^?1 during 1984 and 1985, respectively. Mean adaxial and abaxial stomatal conductances were 0.86 and 1.46 cm sec^?1, during 1984, and stomatal conductances were similar for both years. Stomatal conductance did not appear to limit gas exchange in potato leaves. Dry matter partitioning to tubers ranged from 8.9% for Pungo to 55.5% for Atlantic 67 DAP during 1984. At final harvest, July 19, 1985, dry matter partitioning to tubers varied from 47.5% for Pungo to 69.9% for Chipbelle. The tuber yield ranged from 9.6 to 27.8 MT/ha. This study indicated that Atlantic and La Chipper have potential for growing in a warm climate.     

Reliability of pelvimetry is affected by observer experience but not by breed and sex: A cross-sectional study in beef cattle

Pelvis size plays an important role to prevent dystocia in cattle caused by the foeto-maternal disproportion in commonly primiparous females. The reproducibility and repeatability are two important aspects for the reliability of the measurements to use in the selection of cattle for culling. Pelvic measures were taken with a Rice pelvimeter from 224 young cattle (180 females and 44 males) of four beef breeds in South Africa. One experienced and two inexperienced observers each measured pelvic height and width twice. The proportion measurements with a maximum difference of 0.5 cm within animal compared with the first measurement by the experienced observer are around 80% and by the inexperienced observers around 50% for pelvic height and around 60% for pelvic width. Breed and sex do not affect the reliability of pelvimetry by an experienced observer. Under- and overestimation of pelvis size were observed in inexperienced observers, which seems to be unrelated to breed and sex.     

Foliar Application of Urea and Triazone Nitrogen to Cotton

Upland cotton (Gossypium hirsutum) requires adequate nitrogen (N) for optimum yields. Foliar applications of urea to supplement soil applied N have been tried for many years across the Cotton Belt, but responses have been highly variable. No published information is available regarding response by irrigated cotton to foliar applied N in subtropical South Texas. This study investigated the response of cotton to foliar applied urea and triazone N over a three-year period near Weslaco, Texas. In all years, foliar applied urea tended to increase seed cotton yield when soil applied N was limiting. In the absence of soil applied N, the increase due to foliar urea was significant in two of the three years (28.7 and 15.7% increases). Foliar applied triazone N was ineffective at increasing seed cotton yields.     

Indicators of Cotton Nitrogen Status

ABSTRACT

Nitrogen (N) deficiency limits cotton yields, while too much N causes excessive vegetative growth hurting yields, wastes expensive inputs, and causes environmental pollution. Diagnostic indicators are needed to assess cotton N status so that yields can be optimized as efficiently as possible. This study evaluated selected tools for predicting cotton responses to N fertilizer application. Petiole nitrate (NO₃)-N (PNN) concentration was found to correlate with cotton N status and a good indicator of potential for response to N application. Critical PNN concentrations for irrigated cotton in subtropical South Texas at first bloom, and 10, 20 and 30 d later were determined to be 15.0, 9.0, 4.5, and 2.0 g kg^{? 1}, respectively. These critical PNN levels are higher than in more humid areas of the traditional southern US Cotton Belt, probably due to the effects of the subtropical climate. Cotton plants in this area tend to be less vegetative, possibly due to shorter growing season day lengths, and therefore need to be “pushed” slightly harder with greater N fertilization. Leaf total N concentrations were found to be less responsive to changes in applied N than were PNN levels. Although leaf N tended to be more stable over time, there was no consistent pattern between years. Leaf N values of 35 g kg^{? 1} or less appear to represent a deficiency at any time, and optimum levels may be slightly higher. Nodes above white flower showed very small responses to N fertilization and the differences occurred late in the bloom period. Chlorophyll meter readings showed a good relationship with N fertilizer application within a given sampling date, but much greater variability occurred between dates and due to other factors. The most effective indicator of cotton N status was found to be PNN, and to a lesser extent leaf N, but none of other parameters could be recommended for purposes of making inferences as to N status of cotton.     

Coastal Chip: A chipping potato variety resistant to heat stress

Coastal Chip is a medium-late maturing potato chipping variety suitable for production in locations along the east coast of the United States where heat stress reduces internal quality of tubers. It yields as well as the variety Atlantic but is not as susceptible to heat necrosis. The specific gravity of Coastal Chip averages approximately 0.010 less than Atlantic at locations subject to heat stress. In the seed producing areas of Maine it’s specific gravity averages approximately 0.005 less than that of Atlantic. Tubers are round, netted-skinned, and have moderately deep stem and bud ends. Chips from Coastal Chip are slightly lighter in color than those produced by Atlantic. In mid-Atlantic states where heat stress adversely affects chip color Coastal Chip processes into chips for a slightly longer period of time after harvest than does Atlantic. Glycoalkaloid content of Coastal Chip averaged 7.9 mg/100 g fresh tissue. Sunburned (green) tubers of Coastal Chip develop purple streaks that remain following processing. Hills must be properly covered to reduce losses. Coastal Chip is resistant to race A of the golden nematode (Globodera rostochiensis) and potato virus A. It is tolerant to Verticillium wilt, more susceptible to common scab and Rhizoctonia than Atlantic and susceptible to potato virus X.