NUTRIENT DISORDER SYMPTOMOLOGY AND FOLIAR CONCENTRATIONS OF CLERODENDRUM THOMSONIAE

Clerodendrum thomsoniae plants were grown in silica sand culture to induce and photograph nutritional disorder symptoms. Plants were grown with a complete modified Hoagland's all nitrate solution. The nutrient deficiency treatments were induced with a complete nutrient formula minus one of the nutrients. Boron toxicity was also induced by increasing the element ten times higher than the complete nutrient formula. Reagent grade chemicals and deionized water of 18-mega ohms purity were used to formulate treatment solutions. The plants were automatically irrigated and the solution drained from the bottom of the pot and captured for reuse. The nutrient solutions were completely replaced weekly. Plants were monitored daily to document and photograph sequential series of symptoms as they developed. Typical symptomology of nutrient disorders and critical tissue concentrations are presented. Plants were harvested for nutrient analysis when initial symptoms were expressed. Nutrient deficiency symptoms were described and foliar nutrient concentrations provided.     

Hydrochemical Impacts of Limestone Rock Mining

Hydrochemical impacts of shallow rock industrial-scale mining activities close to sensitive constructed and natural wetlands were investigated. The shallow surficial groundwater and surface water in the Everglades Agricultural Area (EAA) were characterized. The chemical composition of sulfate and chloride in groundwater increased with depth. The average concentration of chloride averaged 182 mg?L^?1 at 6 m deep and increased gradually to 1,010 mg?L^?1 at 15 m deep, 1,550 mg?L^?1 at 30 m deep to reach 7,800 mg?L^?1 at 60 m deep. Comparatively, the surface water chemical composition in the surrounding areas showed much lower cationic and anionic charge. The specific conductivity and total dissolved solids of surface water in canals (close to the mining operations) are <900 ??S?cm^?1 and <600 mg?L^?1, respectively, which should be compared to groundwater quality in wells from the EAA area (>2,000 ??S?cm^?1 and >1,000 mg?L^?1, respectively). A steady-state groundwater fluid flow and transient solute transport modeling exercise was conducted to estimate surface/groundwater interactions. The modeled solute in surface water was transported downgradient through groundwaters, migrated approximately 30 m from the source area (after 5 years of operation), and needed more than 116 years to dissipate. An upward transport was also identified whereby chloride and sulfate, naturally present in deeper groundwaters, migrated approximately 200 m (after 1 year of mining) into the pristine shallower aquifer and reached the surface water with a concentration equaling 80% of that in the rock mining pit.     

Effect of Timing of Seed Deployment on Growth and Mortality of Oysters, Crassostrea virginica, Affected by Juvenile Oyster Disease (JOD)

Abstract.— Mortality of oysters, Crassostrea virginica , caused by Juvenile Oyster Disease (JOD) has been a chronic problem the northeastern United States since 1988. To assist in identifying potential health management options, the effect of time of spawning and deployment of oysters on resultant growth and mortality was examined in the Damariscotta River, Maine. Broodstock oysters from a line selected for fast growth were spawned at 2-wk intervals between 28 March and 19 July 1995. Duplicate groups of juvenile oysters from each spawn were deployed in floating trays between 23 May and 31 August. Mortality and size of all cohorts were determined from late June to early December. Cumulative mortality of oysters was related to the timing of deployment. Cohorts placed in the river before June or after mid-August had cumulative mortalities of 20% or less. Oysters deployed between 8 June and 18 August had cumulative mortalities ranging from 64–96%. Growth of all cohorts was rapid immediately after deployment but decreased once JOD began to have an effect. Final size of oysters was directly related to age. This study determined that seed oysters placed in the Damariscotta River between June and mid-August will experience high mortality and low growth. Potential management options to reduce JOD impact include 1) early spawning and deployment in May, ensuring that a mean shell height >25 mm is reached prior to August and 2) late spawning and deployment after mid-August to avoid exposure to JOD.     

Compensation-Induced Yield Gains in Mixtures of Common Bean (Phaseolus vulgaris L.)

Over the course of two planting seasons field trials were conducted at the CIAT farm in Palmira (Colombia). The experiments included nine tropical bean lines grown in pure stands and seven mixtures obtained by combining these lines on the basis of equal proportions in seed number.
In the case of several pure lines, inferior seed quality led to low germination and uneven population densities, especially in the first planting season. Analogously, missing plants also occurred with the corresponding mixtures. A significant and positive relationship between mixing induced yield gains and patchiness in mixtures was found, indicating that intergenotypic compensation was a major determinant for mixture effects on yield. In common bean as a tropical subsistence crop seed quality is known to be erratic. It is concluded that compensation effects in mixtures of common bean may be expected to be of practical importance regarding the improvement of yield stability over seasons.     

Influence of high temperature on the performance of some Phaseolus species at different developmental stages

Summary The effect of short term high temperature exposure on the performance of five Phaseolus species and of long term (continuous) exposure on the performance of P. vulgaris was studied at three growth stages. Phaseolus species subjected to 26.7, 32.2 or 37.3°C for two days showed small differences in the number of pods produced and in visual leaf damage, but large differences in leaf heat killing time, as measured by conductivity. P. coccineus had the shortest heat killing time (20–60 minutes) and P. acutifolius and P. lunatus the longest times (180 and 153 minutes), respectively. The P. vulgaris genotypes were intermediate in killing times to P. acutifolius and P. coccineus. Species response was not consistent with temperature within developmental stage. On average, the number of pods decreased as temperature increased from 32.2 to 37.3°C. Heat killing time and leaf damage also increased with temperature. CO₂ exchange rates of plants grown at prolonged high temperatures (30–40°C/20–30°C, day/night) decreased with the age of the plant. Shoot lenght was decreased as high temperature. P. vulgaris genotypes differed on the basis of either short term exposure or of continuous exposure. These results suggest that there may be useful germplasm in Phaseolus for improving heat tolerance.Scientific Journal Series Paper Number 13,8000 of the Minnesota Agricultural Experiment Station, USA.