Head Fresh Weight Research Articles

Growth, Development, and Yield of Head Lettuce Cultivated on Paper and Polyethylene Mulch

Lettuce plants (Lactuca sativa L. cv. Ithaca) were transplanted into organic soil and onto beige paper, black paper, and coextruded white/black polyethylene mulches in 1997 and 1998. A weeded bare ground plot was also tested. Transplanting in 1997 occurred in July under warm and dry conditions. Plants grown on mulch established better when the mean air temperature during the week after transplanting was 22.5 °C. The mortality rates of the bare ground control were 30%. All mulches significantly reduced plant mortality in 1997. In 1998, air temperature during the week after transplanting (June) was 14.6 °C. Plant mortality in 1998 was 1.3% for the control and 1.5% for the mulched plots. For both years, plants grown on mulched plots had higher relative growth rates than the control at the start of the season. Head fresh weight was 3.6 times (1997) and 1.2 times (1998) greater for lettuce grown on mulch compared with lettuce grown in a weeded control. Soil bulk density was lower under mulch than in the control plots in 1997.

Towards optimization of growth via nutrient supply phasing: nitrogen supply phasing increases broccoli (Brassica oleracea var. italica) growth and yield.

A greenhouse experiment on broccoli (Brassica oleracea var. italica, cvs Windsor and Arcadia) was carried out in order to demonstrate that supplying nitrogen (N) to meet the nitrogen demands of plant growth stages, through N phasing, improves plant growth and yield, as compared to fertilizing at the conventional, optimal, constant N rate. Two broccoli cultivars and two rates of starter nitrogen fertilizer (optimum, 250 mg l(-1) and sub-optimum, 150 mg l(-1)), were combined with three timings of fertigation change. Shifting N rate, at 60% and 75% of the market plant growth cycle significantly increased shoot dry weight and head fresh weight, compared to the constant-N rates treatments (controls). The highest yield and shoot dry weight were obtained when the N-rate was switched from the optimum level (250 mg l(-1)) to the sub-optimum level (150 mg l(-1)) at inflorescence initiation. The nitrogen-to-growth-stage-fitness effect was determined and partitioned into rate effect and phasing effect. The phasing effect was greatest, on both shoot dry weight and head fresh weight, at inflorescence initiation, and subsequently decreased until harvest time. None of the interactions was significant. The results demonstrated the superiority of nitrogen supply phasing over the conventional fixed-rate-supply method.

Utilização do 'não tecido' de polipropileno como proteção da cultura de alface durante o inverno de Ponta Grossa - PR

O experimento foi realizado na UEPG, Ponta Grossa, PR. Estudou-se o efeito da proteção com 'não tecido' de polipropileno sobre o desenvolvimento, a qualidade e a produção de três cultivares de alface, transplantadas no inverno de 1998. O delineamento experimental foi inteiramente casualizado, distribuído segundo esquema fatorial 3x2 (cultivares x sistema de cultivo), com 5 repetições. As cultivares utilizadas foram Tainá, Elisa e Verônica, cultivadas sob a proteção do 'não tecido' de polipropileno (PP) e em ambiente natural (AN). O uso do 'não tecido' como proteção de plantas de alface resultou em maior peso de matéria fresca de cabeça para todas as cultivares estudadas quando comparado ao AN. Verificou-se, para as cultivares Tainá e Verônica, incremento do índice de área foliar, com conseqüente aumento da biomassa das plantas produzidas sob o 'não tecido'. A cultivar Elisa apresentou limbo foliar com aspecto de estiolamento, perdendo a turgidez rapidamente após a colheita. Possivelmente, os níveis de radiação sob PP foram inferiores ao ponto de saturação fotossintética para a cv. Elisa. Recomenda-se o uso do 'não tecido' para as cultivares Verônica e Tainá, no inverno, para a região de Ponta Grossa, por apresentarem cabeças com ótima qualidade e peso comercial.

Adaptation of hypopharyngeal gland development to the brood status of honeybee ( Apis mellifera L.) colonies

We studied pollen consumption, head weight, hypopharyngeal gland (HPG) acini diameter, and protein synthesis and transfer in honeybee workers reared in colonies with normal and with decreasing amounts of brood. We found that head fresh weight is correlated with size of the glands and that pollen consumption is positively correlated with gland development. An effect of brood on size of the glands could be confirmed, but was not as profound as in previous studies. Similarly, no difference in the amount of protein synthesized or transferred in workers living under the two brood conditions was found. We suspect this is due to the fact that HPGs also supply food to young bees and in our study young bees were always present while in previous studies, colonies often lacked both brood and young bees.

Effects of nitrate, ammonium and chloride application on the yield and nitrate content of soil-grown lettuce

SummaryThe effect of nitrogen availability and nitrogen form on the yield and nitrate content of butterhead lettuce (Lactuca sativa var. capitata L.) grown in soil under greenhouse conditions was studied. The extent to which chloride application can reduce nitrate content by supplying the plant with an alternative osmotically active anion, and whether the presence of ammonium in the soil is a necessary prerequisite for an effect of chloride, was also examined. Reducing NO3-N availability from 260 to 200 kg N ha–1 significantly reduced nitrate content while head fresh weight was unaffected. Further reducing NO3-N availability to 120 kg N ha–1 significantly reduced both nitrate content and fresh weight. Substituting 40% of the available NO3-N with NH4-N significantly reduced nitrate content while fresh weight was unaffected. The effect of NH4-N application on plant nitrate content was enhanced by the application of the nitrification inhibitor dicyandiamide (DCD). Despite increasing chloride uptake, the application of chloride had no significant effect on head fresh weight or nitrate content when available nitrogen was in the nitrate form irrespective of the level of nitrogen application. Chloride application similarly had no effect on head fresh weight or nitrate content when applied together with ammonium without the nitrification inhibitor DCD, despite a greater uptake of chloride. Where both ammonium and DCD were applied, however, chloride application significantly reduced head nitrate content.

Influence of Various Polyethylene Mulch Colors on Growth and Development of `Vates' Collards

The effect of various mulch colors (black, yellow, red, blue, white, and aluminum) on growth and development of `Vates' collards was evaluated in Fall 1996 at the E.V. Smith Research Center in Shorter, Ala. Black polyethylene mulch was installed onto raised, fumigated beds, then sprayed with a 1: 2 (v/v) mixture of exterior oil-based enamel paint to paint thinner with one of the five mulch colors listed. Five-week-old plants were transplanted into beds. Beginning two weeks after transplanting and continuing every other week thereafter, heads were harvested to determine head fresh weight and dry weight. Hourly soil temperatures at 10 cm soil depth were recorded and growing degree days (GDDs) with a base temperature of 4.4 °C were calculated. At two weeks after transplanting, average head fresh and dry weight were highest for the aluminum-colored treatment with head fresh (24.7 and 12.3 g, respectively) and dry weights (2.7 and 1.3 g, respectively) twice that of the yellow treatment (P ≤ 0.05). By four weeks after transplanting and up through the final harvest, marketable yield and average head fresh weights did not differ among the treatments (17,900 kg/ha, 1.4 kg per head, respectively). The red and black mulch treatments accumulated more GDDs than the other treatments, but total marketable yields did not differ among any treatments.

SEED QUALITY EFFECTS ON HYDROPONIC LETTUCE

Achievement of head size uniformity at final harvest reduces loss and increases profitability for the hydroponic lettuce grower. Shoot fresh weight of `Cortina' lettuce (Lactuca sativa L.) at 7 or 21 days after planting (DAP) was inversely proportional to the number of days required for seedling emergence, and was greater for raw than for pelleted seeds. Head fresh weight at final harvest (61 DAP) was directly proportional to seedling length at 21 DAP, but raw and pelleted seeds produced equal head weights. Thus, initial seed (seedling) vigor differences were maintained to final harvest. Osmotic seed priming (–1.5 MPa KH2PO4, 20 h, dark) led to increased germination rate at 15, 25, and 35C; had no effect on germination synchrony; and increased germination percentage only at 35C. Covering raw or pelleted seeds sown in depressions of the phenolic foam trays with fine (No. 5) vermiculite compared to leaving the seeds uncovered, and soaking the trays in hydroponic solution rather than water, increased seedling shoot fresh weights. Seeds sown on their first day of germination or primed seeds gave greater seedling shoot fresh weights than pelleted seeds. However, the more uniform seedling shoot fresh weights from germinated seeds than from primed seeds was associated with more rapid and synchronous seedling emergence.

Utility of Shrimp Sludge from Organic Aquiculture Lagoons as a Soil Amendment for Broccoli Production

Our objectives were to determine 1) if shrimp sludge has any value as a soil amendment in broccoli production and 2) an appropriate rate of sludge for head production. Four levels of N–P–K per 15-L pot (in grams; 2.0 N–0.07 P–1.4 K; 4.0 N–0.14 P–2.8 K; or 6.0 N–0.21 P–4.2 K; and 0.0 N–P–K) were factorially combined and replicated 10 times with four volumes of shrimp sludge (0%, 10%, 20%, and 40% v/w in 15-L pots blended with 100%, 90%, 80%, and 60% Metro Mix 300, respectively). Four-week-old `Emerald City' broccoli transplants were planted into sludge + media–fertilizer mixtures on 12–14–95 and were grown to harvest maturity in a greenhouse. As sludge volume increased, the days to harvest, plant height, and root fresh weight: head fresh weight ratio decreased, but leaf number, fresh weight and area, head fresh weight, stem diameter, and shoot: root fresh weight ratio increased. As N–P–K rate increased, leaf number, area, and fresh weight, stem diameter, head fresh weight, and shoot: root fresh weight ratio increased, but root: head fresh weight ratio and plant height decreased. Using head fresh weight as the determinant, heaviest heads were optimized with 20% sludge and 4.0g N–0.14g P–2.8g K per 15-L pot. Sludge alone or N–P–K alone did not produce the heaviest broccoli heads as using combinations of sludge and N–P–K in a fertility program.

Relation between Head Capsule Width and Fresh Weight in some Caterpillar Species (Lepidoptera: Geometridae, Tortricidae)

The relationship between head capsule width and fresh body weight of some caterpillars was analysed considering 2 linear regression models: Model-1: log(weight) = log(S) + E * log(head width), Model-2: weight = S * (head width) 3 . Both models gave similar results and are good descriptions of the relationship. Nevertheless, model- 2, assuming isometric growth, has some advantages for applications.

Growth, nutrient uptake and tipburn severity of hydroponic lettuce in response to electrical conductivity and K:Ca ratio in solution

A commercial hydroponic nutrient solution formulation was developed to reflect the high K:N uptake of a range of vegetable crops (Huett and Dettmann, Aust. J. Agric. Res. 1992, 43, 1653-65). This standard formulation had a K:N ratio of 1.7: 1.0 and a K:Ca ratio of 1.25 : 1 00 (equivalent weight basis). Head lettuce cv. Coolguard and cv. Fame and non-heading cv. Red Mignonette were grown in recirculating culture to maturity with the standard formulation to examine the effect of electrical conductivity (EC) (0.4-3.6 dS m-l) and, for the latter two cultivars, nutrient formulation K: Ca ratio (from 1.00:3.50 to 3.50: 1-00) on growth, nutrient uptake and tipburn severity. Plants grown at an EC of 0.4 dS m-l were N and K deficient, while recently matured leaves and youngest leaves contained the highest Ca concentrations which decreased with increasing EC. When cv. Coolguard was grown at an EC of 1.0 dS m-l, N and K deficiency was eliminated and leaves contained the highest Ca concentration. Maximum fresh weight of leaf and head was recorded at 1-6 dS m-' and the decline in nutrient solution N and K concentrations over the growth period was 13 and 42% respectively. An increase in the K: Ca ratio of the formulation increased (P < 0-05) leaf by 13% and leaf+head fresh weight at maturity by 10% for cv. Fame whereas, for cv. Red Mignonette, a reduction in the K : Ca ratio increased ( P < 0.05) leaf fresh weight by 29% compared with the standard formulation. A reduction in the K : Ca ratio increased ( P < 0.05) the Ca concentration in the youngest leaves of cv. Fame and of cv. Red Mignonette at 1.6 and 3.6 dS m-l. Leaf K concentrations were generally reduced ( P < 0.05) by low EC and low K:Ca ratio. Hot conditions led to tipburn developing in cv. Red Mignonette at the 2 week harvest. The number of leaves plant-1 with tipburn at maturity (week 3) was reduced ( P < 0.01) from 23.1 to 4.4 as EC was reduced from 3.6 to 0 - 4 dS m-1 and was reduced ( P < 0 05) from 15.2 to 12.3 as the nutrient formulation K : Ca ratio was reduced from 3.5 : 1.0 to 1.25 : 1.00. Over the last week of the growth period, the number of leaves with tipburn remained stable at an EC of 0-4 dS m-l whereas, at 3.6 dS m-l, the number of leaves with tipburn increased by 253%. Tipburn developed in young leaves of cv. Red Mignonette which had a Ca concentration range from 1.7 to 3.2 g kg-1 and was generally absent from recently matured leaves which had a Ca concentration of 11.0 g kg-1. Young leaves of the tolerant cv. Fame had a Ca concentration of 5-9 g kg-1.

Response of Chinese Cabbage to Nitrogen Rate and Source in Sequential Plantings

`Tropical Quick' Chinese cabbage (Brassica rapa L., Pekinensis Group) was planted three times at 2-week intervals in Spring 1991 (direct-seeded) and two times in Fall 1991 (transplanted) in double rows on polyethylene-mulched beds to evaluate N source and rates. Calcium nitrate, ammonium nitrate, urea, urea-ammonium nitrate solution (Uran), and urea-calcium solution (Nitro-Pius) were applied preplant at 67,112, and 157 kg N/ha. The two later spring planting dates, compared with the earliest date, resulted in greater head fresh weights and higher insect damage incidence, but lower tipburn and flowering incidence. The earlier fall planting resulted in greater head fresh weight but a much higher flowering incidence than the later planting. Irrespective of planting date, head fresh weight increased quadratically, and tipburn and flowering incidence decreased linearly with increasing N rate. Although N source affected head fresh weight and tipbum incidence, differences were too small to be of practical value.

Distinction Between Infectious and Noninfectious Corky Root of Lettuce in Relation to Nitrogen Fertilizer

In growth chamber experiments with five concentrations of NH4NO3 and inoculation of lettuce (Lactuca sativa L.) cv. Salinas with Rhizomonas suberifaciens, the causal agent of corky root (CR), symptoms of noninfectious corky root induced by high rates of N were distinct from those of infectious corky root (ICR). Nitrogen toxicity was observed at 350 kg·ha-1 and above, and was not affected by inoculation with R. suberifaciens. There was a curvilinear relationship between concentration of NH4NO3 applied and ICR severity with a maximum at 525 kg·ha-1. In a similar growth chamber experiment with NH4NO3 plus urea, ICR severity decreased and N toxicity increased at increasing N levels (N at 160 to 650 kg·ha-1). In microplots at Davis, Calif., sidedressing with NH4NO3 (N at 170 kg·ha-1) increased ICR severity on `Salinas' lettuce over the nonfertilized control. There was a significant interaction between N fertilization and soil-infestation with R. suberifaciens with respect to head fresh weight: sidedressing with NH4NO3 increased head weight in noninfested plots, but decreased head weight in infested plots. In four field experiments at Salinas, Calif., sidedressing with N at 78 to 213 kg·ha-1, with N as (NH4)1SO4, NH4NO3, urea, or Ca(NO3)2, increased ICR over the control, but there were no significant differences between the forms of N. Head fresh and dry weights were either increased or unaffected by sidedressing with N fertilizers, depending on the residual concentrations of N in the soil. The increase in ICR was likely related to concentrations of soil NO3 rather than NH4.

Effect of nitrogen on growth, quality and nutrient uptake of cabbages grown in sand culture

The effect of nitrogen (N) application level on head yield and quality, growth and nutrient uptake of cabbages (cv. Rampo) was investigated in a sand culture experiment. Plants were harvested at a minimum of 2-week intervals over a 13-week period and N levels (2, 7, 14, 29 and 43 mmol/L as nitrate) were applied each day in a complete nutrient solution which was formulated to provide a stable and balanced nutrient supply. A gamma cubic response surface model fitted actual growth and nutrient uptake data quite precisely (R2 > 0.99) over the range 2-43 mmolb N. This model was used to derive the predicted plant growth and nutrient uptake rates. Head maturity occurred 12 weeks after transplanting when increases in the level of applied N, up to 14 mmol/L, increased the dry weight of roots, stem, leaf and head, and the fresh weight of head. Higher N levels reduced the weight of plant parts. Heads with the lowest percentage of dry matter were produced over the 7-14 mmol/L N application range. Growth rate of tops was low during the 4-week period after transplanting. It then increased rapidly to the maximum predicted value of 43 g/plant.week which was calculated to occur 9 weeks after transplanting at an N application level of 21 mmo/L. Similar growth rates were recorded over the 14-29 mmol/L N application range. Growth rates declined slightly at higher N levels and declined at later growth stages. Predicted nutrient uptake rates followed a similar response pattern to growth rates. The maximum uptake rates (g/plant.week), calculated to occur 8 weeks after transplanting at an N application level of 21 mmol/L, were: N, 1.30; potassium, 2.50; phosphorus, 0.23; calcium, 0.71; magnesium, 0.14; and sulfur, 0.60. We conclude that on low fertility soils, in order to achieve optimum nutrition and hence maximum growth rates and quality of cabbages under field conditions, the application rates of N and K fertilisers need to be flexible to meet the high nutrient demand which occurs after head formation and before final harvest.

Nitrogen and Phosphorus Requirements for Greenhouse Broccoli Production

Abstract ‘Southern Comet’ broccoli (Brassica oleracea L. Group Italica) was grown in a NP deficient soilless medium in 15-liter pots for 45 days in a greenhouse averaging 21°C during the growth period. Fertilizer treatments were split-applied and consisted of factorial combinations of 1.9, 3.7, 5.6 g N (total) per pot from urea and 0.07, 0.14, and 0.21 g P (total) per pot from monocalcium phosphate. Potassium from KCl was split-applied at a constant rate of 1.6 g K (total) per pot. Increasing N rate increased head fresh weight, stem diameter, floret total chlorophyll, root and top dry weight (stem, petiole, leaf, and head), plant height, and head quality, and decreased days to heading and to harvest. Increasing P rates increased floret total chlorophyll, height, and root dry weight to a lesser degree than N. For quality broccoli production in the greenhouse, 5.6 g N, 0.21 g P, and 1.6 g K per 15 liter pot were required.

The Effect of Density and Postplanting Fertilization on Response of Lettuce to CO2 Enrichment1

Abstract Plants of lettuce (Lactuca sativa L. cvs. Parris Island Cos and Great Lakes 659) were grown in greenhouses at 2 spacings and with 2 levels of postplanting fertilization with and without CO2 enrichment. CO2 enriched plants averaged 29% higher head fresh weights and 40% higher leaf areas. In terms of fresh weight increases, enrichment response was greater in ‘Great Lakes 659’ than ‘Parris Island Cos’ and in high rather than low fertility treatments. In terms of leaf area increases, low-density treatments responded more than high-density treatments to enrichment. Increases in leaf area with enrichment were similar in the 2 cultivars and the 2 fertilization treatments.

Influence of Cultivar, Season, Irrigation, and Date of Planting on Thiocyanate Ion Content in Cabbages1

Abstract Tissue analysis of 14 cultivars of cabbage (Brassica oleracea L. Capitata group) in both 1974 and 1975 indicated that late maturing cultivars generally were higher in thiocyanate ion (SCN−) content than early maturing cultivars. In both years, there was a significant positive correlation between SCN− content of cultivars and days to maturity. While SCN− content of late-planted (June 18, 1975) unirrigated ‘Badger Market’ and ‘Storage Green’ cabbages were more than twice as high as corresponding late-planted cabbages irrigated 5 times per week, the SCN− content of early-planted (May 6) cabbages of both cultivars was not significantly influenced by irrigation treatment. In contrast, the marketable head fresh weight of both cultivars was lowest in late-planted, unirrigated plots. Head SCN− content was negatively correlated with marketable head fresh weight and with total top weight of both cabbage cultivars.