Douglas C. Sanders

A humic acid improves growth of tomato seedling in solution culture

Abstract The effects of humic acid (HA) on nutrient accumulation and growth of tomato seedlings were evaluated in a solution of limited nutrient availability in a greenhouse. HA additions were made to the nutrient solution at rates of 0, 640, 1280, or 2560 mg/L. The addition of 1280 mg/L HA produced significant increases in shoot accumulation of P, K, Ca, Mg, Fe, Mn, and Zn as well as increased accumulation of N, Ca, Fe, Zn, and Cu in roots. Fresh and dry weights of roots were also increased, However, on comparing nutrient accumulation in plants treated with 1280 mg/L HA and those given an additional supply of nutrients equivalent to those supplied by HA at the 1280 mg/L rate, shoots accumulated more N, P, K, Fe, and Cu, while roots accumulated more K and Ca. Therefore these increases do not appear to be associated with nutrients contained in HA. Eectrolyte leakage, as an indication of membrane permeability, did not differ as a consequence of HA additions. However, electrolyte leakage correlated positivel...

Effects of irrigation frequency and scheduling on fruit production and radial fruit cracking in greenhouse tomatoes in soil beds and in a soil-less medium in bags

Abstract The effects on yield and radial fruit cracking of 2 media (soil in beds and soil-less medium in bags) and 2 drip-irrigation frequencies (once and 4 times daily) were determined for 4 greenhouse tomato (Lycopersicum esculentum L. Mill.) cultivars. For plants grown in soil-less medium, 2 tensiometer-controlled, drip-irrigation scheduling methods were compared. ‘Michigan’—‘Ohio’ hybrid fruit cracked significantly more than the 3 remaining cultivars, but did not differ in production of total and No. 1 fruit. The amount and severity of fruit cracking was least from the soil-less, bag-cultured plants. Total mean fruit weight was greatest from soil-grown plants. Although no differences in cracking occurred in the fruit from soil-less, bag-cultured plants, those whose irrigation was based on soil-less medium tensiometer readings produced lower total mean fruit weight than those whose irrigation was based on soil tensiometer readings. Number and weight of defective fruit was lowest from plants grown in soil-less medium and whose irrigation was based on soil tensiometer readings, and greatest from soil-grown plants. Fruit cracking was reduced by increasing the irrigation frequency from 1 to 4 times daily.

Drip fertigation with nitrogen and potassium and postharvest susceptibility to bacterial soft rot of bell peppers

Abstract In 1991 and 1992, drip irrigation was used to apply various rates and timings of nitrogen (N) and potassium (K) to black polyethylene plastic‐mulched bell pepper (Capsicum annuum L.) to determine the effect on fruit quality and susceptibility to postharvest bacterial soft rot (Ervinia carotovora subsp. carotovora). Neither rate nor application timing affected total yield in either year. In 1991, the high fertilizer rate (266–309 kg/ha of N and K, respectively) increased class 1 yield in the first harvest and reduced total discards. In 1992, a year with a colder than average spring, the low fertilizer rate (70–81 kg/ha of NK) increased class 1 yield in the first harvest. Mid‐ or late‐season fertigation produced more second harvest yield and less discards than the first harvest in 1991, but not in 1992. Fruits of plants fertilized with high N and K rates had greater N and dry matter concentration. No differences in color or wall thickness at harvest were detected among treatments. Stored fruits tur...

Heat units to predict tomato harvest in the southeast USA

Abstract Planting and first harvest dates of tomato ( Lycopersicon esculentum Mill.) from 2 seasons in 3 years at eight locations in Georgia, North Carolina and South Carolina formed 38 environments which were used to determine the most reliable method to predict fast harvest date of tomato based on daily maximum and minimum air temperature. Eleven methods of calculating heat units were chosen for comparison based on their performance as described in the literature. The most reliable method was defined as the one with the smallest coefficient of variation (CV). CVs were calculated for each method over both seasons and locations, for each season over all locations, each location over all seasons, and for each season at each location. All heat unit summation methods had smaller coefficients of variation (CV) than the standard method of counting days from planting to first harvest. Heat unit summation methods improved harvest date prediction accuracy compared with the counting day method for tomatoes in the South Atlantic Coast (SAC) region. Prediction using location/season specific models were less variable than the models over all seasons and locations. Incorporating daylength improved model prediction accuracy when applied over all locations and seasons, all locations by season, and all seasons by location. Based on the results of this study, the heat unit summation technique recommended for this region (where the location and season specific models are not available) is the reduced ceiling method multiplied by daylength.

Mineral nutrient concentration and uptake by tomato irrigated with recirculating aquaculture water as influenced by quantity of fish waste products supplied

Abstract Fish and tomato (Lycopersicon esculentum Mill.) production were linked in a recirculaing water system. Fish (tilapia) were fed a commercial diet with 32% protein. Tomato cultivars ‘Laura’ and ‘Kewalo’ were grown during summer 1988 and spring 1989, respectively, in a Raleigh, NC greenhouse. Plants were grown in biofilters at 4 plants/m2 and surface irrigated 8 times daily with water pumped from an associated fish tank. Four tank‐to‐biofllter ratios were established by varying the filter size. Each system received identical nutrient inputs and an equal quantity of water was applied per plant. Biofilter drainage returned to the tanks. Biological filtration, aeration, and mineral assimilation by plants maintained water quality within limits for tilapia. All nutrients were assimilated above deficiency levels. Tissue concentrations of N, P, K and Mg were not limiting. Calcium was low and S high when their sole nutrient source was fish waste. Micronutrients were assimilated in excess of sufficiency, but...

Response of European corn borer (Ostrinia nubilalis, Hubner) to two potato hybrids selected for resistance to Colorado potato beetle

The response of the European corn borer, Ostrinia nubilalis (Hubner) to K411-2 and NYL 235-4, fifth- and sixth-generation potato accessions derived from crosses between Solanum tuberosum L. and S. berthaultii (Hawkes) and selected for resistance to Colorado potato beetle (Leptinotarsa decemlineata, Say) and potato leafhopper (Empoasca fabae, Harris), was measured in field and greenhouse experiments. In one field test, which did not include NYL 235-4, the incidence of corn-borer damaged stems was eight times higher in the commercial potato varieties Atlantic, Superior and Norland than in K411-2. In a later field test, there were 11 times more European corn-borer damaged potato stems on Atlantic than on NYL 235-4. In a choice experiment, European corn-borer moths deposited significantly more egg masses on the susceptible Kennebec variety (72.9%) than on NYL 235-4 (27.1%), but in the absence of a choice, equal numbers of egg masses were deposited on both varieties. In a greenhouse experiment, fewer European corn-borer larvae (44%) were established on NYL 235-4 than on Kennebec plants.

Heat units, solar radiation and daylength as pepper harvest predictors

Abstract Daily maximum and minimum air temperature, total solar radiation and daylength data from seven locations during three seasons of 3 years were used to compare 52 heat unit accumulation models with counting days as a harvest prediction method for pepper. The best model was defined as the one with the least variation, i.e. smallest coefficient of variation (CV). CVs were calculated for each method over all seasons and locations, for each method over all locations for each season, and for each method in each season at each location. In all cases heat unit accumulation methods were better than counting days. The location and season specific model was the most accurate, but the analysis over all seasons and locations did result in smaller CVs than counting days, so improved harvest prediction can be achieved by using regionally developed models.

Nitrogen uptake within sequential vegetable cropping Systems 1 , 2

Abstract A study was conducted to determine the effect of previous crop, nitrogen (N) rate and planting density on N uptake within different vegetable cropping sequences. Spring crops included tomato (Lycopersicon esculentum Mill.), snap bean (Phaseolus vulgaris L.) and sweet corn (Zea mays L.). Each spring crop was followed in the fall by broccoli (Brassica oleracea L. Italica group), collard (Brassica oleracea L. Acephala group) and pumpkin (Cucurbita pepo L.). Higher N rates resulted in greater N uptake for all plants at some point in the growing season. Final N accumulation exceeded N fertilizer applied at 1 or more N rates for all six crops. However, higher N rates resulted in greater final N accumulation only with the tomato/broccoli sequence. Plants grown at lower density generally had greater N accumulation per plant, but N uptake per hectare was greater for the high density planting. The greatest previous crop effect was in 1984 when N accumulation for pumpkin following tomato exceeded that of ot...

Influence of Cover Crops and Inorganic Nitrogen Fertilization on Tomato and Snap Bean Production and Soil Nitrate Distribution

ABSTRACT Commercial vegetable production depends almost solely on inorganic fertilizers. In an era of environmental sensitivity, enrichment of soils with green manures and cover crops may reduce the dependence on these fertilizers while maintaining and enhancing crop yields. The objectives of this research were to determine (1) if supplemental nitrogen (N) at 60 or 120 kg · ha−1 following winter cover crops of wheat (Triticum aestivum L.) or crimson clover (Trifolium incarnatum L.) affect yield of tomato (Lycopersicon esculentum Mill.) and snap bean (Phaseolus vulgaris L.) grown in rotation; and (2) the distribution and retention of soil nitrates in the soil profile as affected by N fertilization and cover cropping. ‘Mountain Pride’ fresh market tomato and ‘Strike’ snap bean were grown in rotation for four years. Clover and wheat cover crops increased total marketable yield of ‘Mountain Pride’ tomato in one out of four years. Total marketable tomato yield increased as fertilizer N increased to 60 kg · ha−1 in two out of four years and with 120 kg · ha−1 in one out of four years. N did not interact with cover crops to affect yield. ‘Strike’ snap bean marketable yield summed over all years was 60% lower in clover plots compared with fallow. Total marketable snap bean yield increased with 60 kg N · ha−1 in one out of three years but was unresponsive to N in two out of three years. Soil nitrates to 1.2 m depth were higher after clover and wheat than after fallow. Nitrate level was highest in soil with clover and 120 kg N · ha−1. In all cover crop or fallow plots, as fertilizer N application levels increased, the soil nitrates also increased. Cover crops or fertilizer N application did not increase the retention of residual nitrates in the 1.2 m soil profile depth after four years of cropping.