Search Results

You are looking at 41 - 50 of 63 items for

  • Author or Editor: Donald N. Maynard x
Clear All Modify Search

Abstract

The visual recognition of abnormal plant growth caused by faulty nutrition has been widely used in diagnosis and subsequent remedial action to restrict crop losses. Fortunately, symptoms of nutrient imbalance are usually quite characteristic and can be readily identified by the trained observer.

On occasion, however, visual symptoms may be masked or occur as a syndrome. In these cases it may be necessary to make major investigations into the chemical, and perhaps physical, characteristics of the soil. Unsuitable soil pH, excessive salinity, or severe nutrient imbalance are major causes of a complex of symptoms rather than those which are typical of a single element imbalance. Despite these exceptions, we believe that the visual method of diagnosis provides the most rapid means of identifying the commonly encountered nutritional problems.

General descriptions (8, 9, 11, 12) of nutrient disorders, keys (1, 10, 14, 17) and detailed descriptions for individual elements and crop plants (3, 4, 13, 16) are found in the literature. This key for nutritional disorders of vegetable crops was developed to provide detailed, yet concise, information on these crops. We believe that it will be useful as a teaching aid in vegetable crops and plant nutrition, and as a working key for diagnosis of field nutritional problems.

Open Access

Abstract

Undergraduate interest in courses and curriculum in the agricultural sciences, including horticulture and plant and soil sciences (1), is at an all time high. Enrollment in agriculture in member institutions of the National Association of State Universities and Land-Grant Colleges more than doubled from 1963 to 19743. This paper describes changes that have been made in the Department of Plant and Soil Science at the University of Massachusetts to serve our students and provides a vehicle for future changes in undergraduate horticultural education. Hopefully, other departments will report on their undergraduate activities so that others may benefit from their experience.

Open Access

Abstract

The effects of replanting stand-deficient plots on marketable tomato (Lycopersicon esculentum Mill.) fruit size and yields were investigated at Bradenton, Fla. during the 1986 spring and fall seasons. Treatments consisted of a control (10-plant plot) and plots with 9, 8, and 7 (10%, 20%, and 30%) missing plants. Other plots with the same stand deficiency were replanted to attain a complete stand 2 or 3 weeks and 1, 2, or 3 weeks after initial transplanting in the spring and fall experiments, respectively. Plots with 30% stand reduction produced a lower weight and number of marketable fruit per hectare than control plots in both seasons. In spring, replanting stand-deficient plots did not increase marketable fruit yields relative to plots not replanted, regardless of the time of replanting or percentage of stand reduction. In fall, under an unfavorable environment due to a late infestation of bacterial spot, replanting plots with 30% stand reduction increased marketable fruit yields over similar plots that were not replanted, when the replanting occurred 1 or 2 weeks after initial transplanting, but not when replanting was delayed 3 weeks. Small, medium, or extra-large marketable fruit weight per hectare were similar in both seasons for plots with 30% stand reduction, whether replanted or not. Mean fruit size (g/fruit) did not differ significantly among treatments in either experiment. These results suggest that replanting improved marketable tomato yields only when the level of stand deficiency reached 30% and only in a stressed environment.

Open Access

Abstract

Transplants of asparagus (Asparagus officinalis L.) were grown in sand culture under varying ratios of NO3 and NH4. Maximum growth occurred in a nutrient solution with a N ratio of 75% NO3 – N and 25% NH4 – N. Growth was significantly reduced when the N composition was either 100 or 75% NH4 – N. CaCO3 reduced ammonium toxicity but also reduced seedling growth.

Open Access

Abstract

Spinach, Spinacia oleracea, L., cv. America, Heavy Pack, and Hybrid 424 were grown in sand culture with variable NO3 concentrations from 0.187 to 48 meq/l. The cultivars were representative of savoyed, semisavoyed, and smooth-leaf types, respectively. The plants were harvested when those cultured at 12 and 18 meq NO3/l had obtained approximate market maturity. At this time an array of deficiency, sufficiency, and toxicity symptoms were evident. Great differences in NO3 accumulation and critical NO3 concentrations occurred among cultivars. Critical NO3-N concentrations for the whole leaves of spinach plants were: ‘America’, 0.17%, ‘Heavy Pack’, 0.15%, and ‘Hybrid 424’, 0.045% of their dry weights. Calculations relating spinach consumption and impaired human health suggest that adult health should not be affected even with massive ingestion of spinach.

Open Access

Abstract

Brussels sprouts (Brassica oleracea var. gemmifera, Zenker) were grown in sand culture at variable Ca levels in the greenhouse. More Ca accumulated in leaves than in sprouts. With plant growth restricted by late seeding and low greenhouse temp, typical Ca deficiency symptoms occurred on the growing points of plants cultured at low Ca levels, but internal browning did not occur. When growth was enhanced by cultural modifications, sprout internal browning occurred at low Ca levels and decreased as Ca levels were increased. The incidence of internal browning was related to low Ca concn in sprouts.

Open Access

Abstract

The accumulation of cations and NO3-N was higher in cucumber shoots than in pea shoots grown on nitrate nutrition. Total N concn in shoots did not differ between the species. Ammonium nutrition suppressed cation accumulation in cucumbers but not in peas. Differences in cation accumulation in the shoots are attributed to the form in which N is translocated from root to shoot.

Open Access

Abstract

Seedlings of 44 tomato strains were screened in low (16.5 mg/plant) Ca nutrient solutions. Tolerance to low Ca was rated according to plant appearance and efficiency ratios, i.e., tissue produced (g) per unit of Ca (mg) in the tissue. Correlations among various symptom ratings and Ca-efficiency ratios for roots, stems and petioles, and laminar tissue showed that only 1 deficiency symptom and dry weight or 1 symptom and 1 efficiency ratio were necessary to rank plants. These methods showed that Plant Introductions (PI) 340909, 341984, and 341988 (all L. esculentum) were Ca-inefficient, whereas PI 205040 (L. esculentum cv. Yellow Peach) and PI 129021 (L. esculentum × L. pimpinellifolium) were Ca-effi-cient. Differences in efficiency were maintained when these selections were grown with higher Ca concentrations.

Open Access

Most cultivars of tropical pumpkin (Cucurbita moschata Duchesne) are large, trailing plants. New semi-bush (SB) genotypes need to be tested against traditional long vine (LV) types. Both types of pumpkin have large amounts of interplant space during the early stages of growth that might allow for the planting of an intercrop. To test this hypothesis, as well as the performance of tropical pumpkins of varying growth habit, double rows of beans (Phaseolus vulgaris L.) or cowpeas [Vigna unguiculata (L.) Walp.] were intercropped between rows of SB or traditional LV tropical pumpkin in Spring and Fall 1993 in Lajas and Isabela, Puerto Rico. In general, interactions between intercrop treatment and pumpkin genotype were not significant. At its maximum percentage cover (MC) the LV genotype covered, or nearly covered, the entire plot while the SB genotype covered 50% of the plot or less. The SB pumpkin was harvested 5 to 27 days earlier than the LV type. Yield was two to 12 times greater, and average fruit size three to six times greater in the latter. Planting of an intercrop did not reduce pumpkin yield. Green-shelled yields of intercropped legumes averaged ≈700 kg·ha-1. Genotype of the pumpkin maincrop did not affect legume green-shelled yields in Lajas. In Isabela, legume green-shelled yields were 50% higher in SB than in LV pumpkin plots. Legume dry grain yields were greatly reduced in LV compared to SB plots. Intercropping of tropical pumpkin with a short season legume that can be harvested green-shelled is an efficient intercropping system that offers additional yield from the legume without sacrificing yield from the pumpkin maincrop. Both SB and LV pumpkins can be used in an intercrop system, but pumpkin yields were much greater with the LV genotype.

Free access