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  • Author or Editor: D. Ron Earhart x
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The active ingredient of a product known as “AmiSorb” is carpramid, a long-chained polyaspartate polymer. This product is currently being marketed as a soil or irrigation water applied nutrient absorption enhancer for vegetable crops. Our objective was to evaluate the growth, yield, and leaf photosynthetic responses of muskmelon (Cucumis melo L., `Caravelle') and bell pepper (Capsicum annuum L., `Enterprise') to a range of carpramid application rates under well irrigated and fertilized conditions. Carpramid solutions were applied at concentrations of 0, 200, 400, 600, and 800 mL·L-1 (0 to 0.18 mL per carpramid plant) in both greenhouse and field experiments. Biomass of individual plant parts and leaf area were measured at weekly intervals during the greenhouse experiment by destructive sampling. Light saturated leaf photosynthetic rates as a function of both carpramid treatment as well as leaf position on the vine were measured for muskmelon in the field experiment. Final yield was determined for both muskmelon and bell pepper in the field experiment. None of the plant response variables were significantly (P ≤ 0.05) affected by carpramid treatment in either the greenhouse or field experiments. Leaf photosynthetic rates increased from the youngest leaf on the vine to the sixth leaf, counting basipetally. We conclude that further research under nutrient deficient conditions may be warranted for this product.

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The objectives of this study were to determine if the use of leonardite as a fertilizer supplement improved crop growth and if there was a residual effect from previous applications. Three planting sequences were established and leonardite applied at 0, 50, 100, 200, and 400 lb/acre (0, 56.1, 112.1, 224.3 and 445.6 kg·ha−1). Subplots were treated at the first, the first and second, or all at three planting sequences. `Purple Top White Globe' turnip (Brassica rapa L.) and `Florida Broadleaf' mustard greens (Brassica hirta L.) were used as the indicator crops in the first two and last sequences, respectively. No differences in plant growth were observed among number of applications or treatment rate. Differences in soil potassium and iron were observed.

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Eight individual potatoes, exhibiting a wide range of quality characteristics, were cloned at the Texas A&M Vegetable Improvement Center, College Station, Tex., in order to produce a large number of slips for field trials. Leaf photosynthetic light response for six of these clonal selections was determined during a greenhouse experiment conducted at the Texas A&M Univ. Agricultural Research and Extension Center at Overton, Tex. Photosynthesis data were fit to a rectangular hyperbola in order to estimate light saturated leaf photosynthetic rate (Amax), quantum efficiency (QE), and dark respiration rate (Rd). Significant differences (P ≥ 0.05) were detected in all three of these parameter estimates among the six clonal selections. Parameter estimates ranged from 23.4 to 28.8 μmol (CO2) m-2·s-1, 0.056 to 0.071 mol (CO2)/mol (photons), and –0.9 to –2.0 μmol (CO2) m-2·s-1 for Amax, QE, and Rd, respectively. However, these differences were not clearly related to quality characteristics determined for these clones in field trials.

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