Evaluation of carrot and onion cultivars for commercial production in Guyana

Experiments were conducted at two locations (Central Agricultural Station, CAS, Mon Repos, and Black Bush Polder) in Guyana, to evaluate carrot and onion cultivars for adaptability to the climatic conditions. Onion cultivars were tested for the production of dry bulbs as well as for the green tops.‘Chantenay Red Core’, ‘Improved Danvers-126’, ‘Nantes Strong Top’, ‘Nantesa Superior’, and ‘New Kuroda’ carrot produced average yields between 14 and 25 t/ha. Dry bulb yields of ‘Bermuda-986’, ‘Granex’, ‘Red Creole’, ‘San Felipe’, and ‘White Creole’ onion were lowest of all cultivars included in these trials. At the CAS, ‘Texas Grano-502’ and ‘White Alamo’ produced larger onion bulbs with average weights of 82 and 77 g, respectively. At Black Bush Polder ‘El Toro’ produced the largest onion bulbs with an average weight of 77 g. In storage, bulb losses for red onion cultivars, ‘Red Creole’, ‘Red Granex’, ‘Tropicana’, were lowest at all samplings during the 82 days storage period. White onions were most susceptible to loss in storage. Average losses of white onions were 33.3, 63.7, 74.6 and 86.2% at 21, 44, 55, and 82 days in storage, respectively. Storage losses for ‘White Creole’, which was an exception, were 11.1, 35.9, 46.4, and 57.0% for the above-mentioned storage durations respectively. Among four cultivars evaluated for green onion production, ‘Evergreen Bunching’ produced the highest yield (28.6 t/ha).     

Weed management in onion using chemical,non-chemical,and manual methods

Summary

Weed management studies in onions grown from seedlings were conducted during 2006 and 2007 at the National Agricultural Research Centre, Islamabad, Pakistan. Applications of pendimethalin at 0.825 l a.i. ha^–1, or oxadiazon at 0.240 l a.i. ha^–1, 2 d after transplanting (DAT) seedlings were evaluated alone, and in combination with one manual weeding, for their effects on weed competition and bulb yields. Other weed control treatments included the application of rice straw mulch 2 weeks after transplanting (WAT) combined with one manual weeding at 9 WAT, or a newspaper and rice straw mulch applied 2 WAT. Compared to the weed-free situation, competition with weeds caused reductions in bulb yields of 62% and 68% during the first and second year, respectively. Polygonum plebejum, Amaranthus viridis, Cyperus rotundus, and Coronopus didymus were the dominant weeds recorded in the field. Mulching reduced weeds by 56 – 60% compared to the chemical weed treatments. Compared to the weed-free treatment (four manual weedings at monthly intervals), which is a traditional method to control weeds in onion, bulb yields increased significantly under the rice straw mulch or when treated with pendimethalin in combination with one manual weeding at 9 WAT. The latter two treatments, on average, resulted in the highest increases of 26 t ha^–1 and 24 t ha^–1 in bulb yields with net returns of US$ 1,522 ha^–1 and US$ 1,486 ha^–1, respectively over the non-treated control.     

Spacing Experiments on Vegetables: II. The Effect of the Thinning Distance on the Yields of Globe Beet,Long Beet,Carrots and Parsnips Grown at a Standard Inter-Row Distance in Cheshire, 1948

Crosses were made in all possible combinations, between winter cauliflower varieties Tinribs and Cambridge Dwarf April, summer cauliflower variety Cambridge 5 and autumn cauliflower variety Majestic. When sown at their normal times these types mature in December, March, June, and September respectively. Data on the maturity periods for parents and Fi and F2 progenies were obtained in the form of accumulated day-degrees.

When all parents and progenies were sown at a date near to the normal sowing date for autumn and winter cauliflowers, the F, and F2 generations showed a continuous range in maturity periods between those of the parents and, although the F2 range was generally greater than that of its corresponding Fi, it did not exceed the parental extremes. When the sowing date was near that for summer cauliflowers, the Fi and F2 progenies of crosses which had Cambridge 5 as one parent matured almost as early as Cambridge 5, and the range of maturity was greatly restricted.

The annual habit of the summer and autumn types was considered to be partially dominant to the biennial habit of the winter types, and time of maturity was considered to be under polygenic control.

Possible improvement of the autumn cauliflower type by making crosses between summer and winter cauliflowers is discussed.     

Apple tree growth and overall fruit quality under organic and conventional orchard management

Two apple (Malus × domestica Borkh.) orchards, a conventional and an organic one, were compared in terms of plant growth, marketable fruit quality attributes (fruit weight, shape, color, phenolic compound concentration, nutrients) and yield. The two orchards were located nearby, in order to exclude possible pedoclimatic influences on the measured variables. The two management systems resulted in similar new season's shoot growth and similar fruit quality attributes, in terms of total soluble solids, juice pH, titratable acidity and color indexes, while the conventionally grown trees produced almost twice the yield of the organically managed ones. The flesh plus peel portion of the conventionally produced fruits exhibited higher total flavonoid and o-diphenols concentration, while the flesh portion presented higher flavonoid concentration. Nitrogen concentration was higher in all portions of conventionally grown fruits, while potassium, calcium, sodium and manganese concentrations were higher in the flesh portion of organically produced fruits. Significant differences were observed between management systems concerning fruit nutrient ratios, but their values were within the desired ranges, under both conventional and organic management systems.     

Differences in onion pungency due to cultivars,growth environment,and bulb sizes

This study was conducted to determine the effects of genetic and environmental factors on onion pungency, estimated as pyruvic acid levels. Genetically identical clones were grown at three different field locations and in a greenhouse. Onion pungency was significantly influenced by clone type, location, and their interaction. Genetic differences were the major determining factor of onion pungency (81.3% of total variation). Location, including all environmental factors, and the clone × location interaction comprised 11.4% and 7.3% of the total variation, respectively. The magnitude of the pungency difference among field-grown onions was about 1.5 μmol/ml. The pungency levels were not positively correlated with soil sulfur nutrition levels, which ranged from 16 to 97 ppm. Within clones, onion pungency levels were loosely inversely correlated with increasing bulb weight. The clones proved to have the most uniform pungency (8% CV), followed by hybrids (10.6% CV) and open-pollinated cultivars (21.3% CV). We have demonstrated that genetic factors were determinant of onion pungency. Environmental factors influenced pungency to a lesser degree. Therefore, choosing cultivars with low pungency, ideal growing environments and proper sulfur nutrition control, are key factor in producing sweet onions.     

Effects of source,rate, and frequency of N application on yield,marketable grades and rot incidence of sweet onion (Allium cepa L. cv. Granex-33)

In a field experiment in the 1988-89 season, fertilizer formulations of NH₄NO₃, Ca(NO₃)₂, NaNO₃, NaKNO₃, and KNO₃ as N sources were applied at 84 and 168 kg N ha^?1 to onion plots direct seeded in the fall. A second experiment in the 1990-91 season tested the same N sources, except KNO₃, at rates of 168 and 224 kg ha^?1. Application strategy involved both splitting the total amount of fertilizer over two periods of the growing season (October–December and January—April) and the application frequency. With medium and high application rates (168 and 224 kg ha^?1), NH₄NO₃, NaNO₃, and NaKNO₃, increased high-value jumbo and large onions (premium marketable grade). Increased premium grades was due to increased bulb size and weight. Only NH₄NO₃ and Ca (NO₃)₂ increased total onion weight when N rate was increased from 84 to 168 kg ha^?1. Less frequent applications of split amounts of 84 kg N ha^?1 reduced marketable weight in the 1988–89 season, but doubling the rate to 168 kg ha^?1 restored the higher yields. At 224 kg N ha^?1 in the 1990–91 season, differences in onion grades were more pronounced among the different N sources, and NH4 NO₃ was superior in producing jumbo and large size onions. High N rates (224 kg ha^?1) and more frequent applications of split portions also increased the weight of jumbo onions. Split applications, providing 33% of the total N in the first 12 weeks of the growth period plus three applications of 22% each in the second 12 week period, increased bulb size and maximized yield of premium marketable grades. Effect of N rate on onion rot was dependent on split methods of applying the N during early and late growth periods. However, reduction in onion rot by the split application strategy was dependent on N source. Bulb decay was highest with NH4NO₃ and least with Ca(NO₃)₂ and NaNO₃.     

不同有机肥施入量对有机蔬菜产量的影响研究

以青刀豆、西兰花、甘薯、胡萝卜和圆葱等主要有机蔬菜为试材,研究不同有机肥施入量对有机蔬菜产量的影响。结果表明:随着施入有机肥数量的增加,5种蔬菜的产量都呈递增的趋势,但施肥量增加到一定量后,有机蔬菜产量提高不明显,差异不显著;667m2地块中青刀豆的最佳施肥量为2000kg;西兰花和甘薯的最佳施肥量为2500kg;胡萝卜和圆葱的最佳施肥量为3000kg。     

The effects of mechanically-induced stress and water stress on freezing resistance in lettuce and cauliflower seedlings

Summary

Mechanically-induced stress, applied by brushing young lettuce and cauliflower plants for 90 s each day, reduced the freezing resistance of cauliflower but had no effect on that of lettuce. Brushing reduced fresh weight in both species and smaller plants were less freezing-resistant than larger ones. The levels of abscisic acid (ABA) in the shoots of brushed cauliflowers were slightly less than in unbrushed plants, whereas in lettuce the levels were similar in the two treatments. ABA sprayed onto lettuce plants had no effect on freezing resistance. With both lettuce and cauliflower, freezing resistance, and the osmolarity of sap extracted from the shoots, increased following water-stress and declined progressively following rehydration.     

Yield and quality of carrots as affected by soil moisture and N-fertilization

Summary

High yield and quality are important factors for growers of carrots (Daucus carota L.). The objective of this study was to determine optimum soil moisture and N-fertilization to maximize carrot yield and external quality (i.e. the quantity of split and forked roots). The experiment was carried out in a microplot field installation with three levels of soil moisture (75, 50 and 25 vol% available field capacity (AFC)) on a sandy and a loamy soil over the last 16 and 11 weeks of the cropping period, respectively. Two movable roofs covered with polyethylene foil were used to maintain the three soil moisture levels, which were measured in all combinations with two levels of nitrogen fertilization (0 and 150 kg N ha^-1). The highest total yields were reached at both soil types at 75 vol% AFC and 150 kg N ha^-1. The quantity of forked carrots was more affected by reduced soil moisture on the sandy soil than on the loamy soil. The mass fraction of split roots increased with increasing soil moisture on both soil types and a significant interaction was calculated between soil type and fertilization. The mass of split roots on the sandy soil was significantly increased by fertilization.     

A validated mechanistic model of carrot (Daucus carota L.) growth

A mechanistic model of carrot vegetative and root development was constructed. This model determined canopy photosynthesis over a day, assimilates were then partitioned into either roots or leaves via temperature dependent partitioning coefficients. Assimilates were lost via terms describing growth and maintenance respiration. The model was calibrated on data from four different carrot cultivars, originating from the UK (Autumn King), Syria (Carrot_S), Poland (Dolanka) and Russia (Hibinskaja), grown in controlled environment glasshouse compartments at one of six temperatures (9–30 °C) repeated over three sowing dates. Calibration of the model showed that it could account for between 83 and 95% of the variance in carrot plant and root dry weights. The model was then validated using independent data from the same cultivars of carrots grown in the field at Reading. In this instance, the model accounted for 75 and 79% of the variance in plant and root weight, respectively. Two other independent data sets were used to validate the model, including carrot of a different cultivar (Panther) grown in phytotrons at temperatures between 9 and 21 °C, at two different locations and over a three sowing dates. In this instance, the model accounted for between 63 and 69% of the variance in root weight. The model also predicted that if ambient carbon dioxide levels increased from 348 to 551 μmol mol⁻¹, root dry weight would increase by 12%, which is within the margin of error of the experimental value of 16% reported in the literature. The model can therefore be used to study the potential impacts of global climate change on carrot production, as well as to rapidly predict whether germplasm is suited to any particular environment.     

Potassium nutrition and postharvest moisture loss in carrots (Daucus carota L.)

Summary

The effect of potassium (K) nutrition on the shelf life of carrots (Daucus carota L., cv. Paramount) was studied using a hydroponic system involving rockwool slabs as an inert support. Carrots were grown for 192 d under greenhouse conditions and with 0, 0.1,1.0,10 and 15 mM K supplied in the nutrient medium. Increase in K concentration in the nutrient medium up to 1 mM decreased postharvest moisture loss. Carrot root weight and tissue K concentration increased, and water potential, osmotic potential and relative solute leakage decreased with increasing K concentration up to 1 mM. Concentrations greater than 1 mM had little or no additional effect on postharvest moisture loss, root water and osmotic potentials and relative solute leakage. Root weight did not increase above 10 mM K. The best subset model obtained by backward stepping and the optimum Mallow’s coefficient showed that carrot root weight and relative solute leakage accounted for most of the variation in moisture loss. Root weight correlated negatively and relative solute leakage positively to moisture loss.     

Physiological response of cauliflower in relation to manganese-boron interaction

Summary

Cauliflower (Brassica oleracea L. var. botrytis) was grown in refined sand at low (0.0011 mg l^?1), normal (0.55 mg l^?1) and excess (5.5 mg l^?1) Mn, each at three levels of B, deficient (0.0033 mg l^?1), normal (0.33 mg H) and excess (3.3 mg l^?1). In Mn deficient cauliflowers a deficiency of B accentuated visible symptoms of Mn deficiency and aggravated the Mn deficiency effects i.e. a decrease in dry matter, leaf Mn, sugars, starch, chlorophyll, Hill reaction and specific activity of aldolase and an increase in the concentrations of proline and inorganic phosphorus. In cauliflowers exhibiting B toxicity symptoms under conditions of excess B, excess Mn increased leaf Mn, sugars, nucleic acids, protein P, nucleic acid P, acid-labile P and leaf B. Excess Mn decreased the concentrations of DNA, protein nitrogen, chlorophyll and activities of peroxidase, aldolase and leaf B, leaf Mn in boron deficient cauliflowers.     

The Effects of Manurial Treatments on The Yield and Quality of Carrot Seed

Seed crops of carrots were grown in 1962, 1963 and 1964, on plots of a 2⁴ N, P, K and farmyard manure factorial experiment. Significant seed yield responses were obtained to each of the fertilizers and to manure, as compared with the yields from the control plot with no manure or fertilizers.

Except when a seed-borne disease caused by Stemphylium radicinum was present, the germination of the ungraded seed was well above the statutory declarable minimum of 60% and there were no significant differences in germination caused by the manurial treatments.

The seed produced in 1963 and 1964 was of similar mean chemical composition to commercial seed and, although its composition was affected by the nitrogen and farmyard manure dressings, these variations in composition did not affect the yield of roots obtained from field sowings of the 1963 seed. The 1962 seed was exceptional in having a lower mean phosphorus concentration than commercial seed. The seed with the lowest phosphorus concentration was obtained from the plots which had received nitrogen but not phosphorus fertilizers, and the root yields from such seed were significantly lower than those from the seed containing higher concentrations of phosphorus.     

Onion yield and quality response to two irrigation scheduling strategies

Irrigation technologies that conserve water are necessary to assure the economic and environmental sustainability of commercial agriculture. This study was conducted in the Rio Grande Valley in Texas to evaluate yield and quality of subsurface drip irrigated onions (Allium cepa L.) using different scheduling strategies and water stress levels. One strategy consisted of initiating irrigation when the reading of a granular matrix sensors (Watermark^{® 1} soil moisture sensor, Irrometer, Co., Riverside, CA) installed at 0.2 m depth reached −20 kPa (optimum), −30 kPa and −50 kPa. The second strategy was to replace 100%, 75%, and 50% of crop evapotranspiration (ETc) weekly. Higher total yields, and jumbo onion size yields were obtained when the soil moisture was kept above −30 kPa. Yields were not affected when water applications were reduced from 100% to 75% ETc and from −20 to −30 kPa. The ETc strategies of 100%, and 75% ETc resulted in similar water usage to the soil moisture monitoring strategies of initiating irrigation at −20 and −30 kPa. Total yields dropped significantly when soil water stress increased below −50 kPa. For the ET based strategy yields also dropped with the 50% ETc treatment. Onion bulb pungency and brix were unaffected by water level.     

松花菜花球的主要营养特点分析

以近4 a来松花菜与普通紧花球花椰菜主要营养品质的测定数据,分析比较了松花菜的主要营养特点.试验结果表明,松花菜花球叶绿素平均含量为12.08μg/g FW,类胡萝卜素平均含量为3.28μg/g FW,可溶性糖平均含量为2.82%,比普通紧花球花椰菜要高出约2.5倍、1.5倍、14.8%,两者在VC、粗蛋白、粗纤维含量方面无明显差异,另外,秋冬季收获的松花菜粗蛋白、粗纤维及可溶性糖含量要高于春季收获的.     

Effect of application methods of organic fertilizer on growth,soil chemical properties and microbial densities in organic bulb onion production

This study was carried out to maximize the fertilization efficiency of mixed organic fertilizer (OF) for organically managed onion (Allium cepa L.) production during the one growing season of 2005–2006. The organic fertilizer was made of organic materials like sesame oil cake, rice bran and molasses and minerals like illite and mountainous soil. Four organic topdressing treatments, which all followed the same basal fertilization with solid OF, consisted of solid OF without mulch (OF/OFnM), liquid organic fertilizer without mulch (OF/LOFnM), liquid organic fertilizer under mulch (OF/LOFuM) and liquid organic fertilizer over mulch (OF/LOFoM). Chemical fertilizer (CF) and no fertilizer (NF) were treated as controls. The solid organic fertilization base was 2.0 ton ha⁻¹, and 4.57 ton ha⁻¹ and was used for topdressing. The total amount of liquid organic fertilization was 133.2 ton ha⁻¹, which was divided into 6 applications from February through March. The OF/LOFuM and OF/LOFoM topdressings did not reduce onion height, leaf number or bulb diameter as compared to chemical fertilizer, whereas no mulch treatments made onion growth significantly poorer. Onion top weight in CF was significantly higher than that in OF groups at the peak growth stage, while there was not much difference in bulb weight between the CF and OF/LOFoM treatment. Finally, the onion marketable yield was 45.9 ton ha⁻¹ in the OF/LOFoM treatment, which exceeded that in the CF treatment by up to 1.9 ton. Furthermore, OF/LOFoM was the most effective among all the treatments in transferring the nutrients from sink to source. CF made the soil pH more acidic than OF did, and the electrical conductivity (EC) remained higher with CF than OF as well. While organic fertilizer helped to keep the NO₃-N content stable throughout the growing season, the concentration rapidly oscillated up and down according to CF fertilization. Organic fertilizer increased population number of soil microorganisms like aerobes, actinomycetes in the field.     

An Approach to the Study of Yearly and other Variation in Crop Yields

The effects of deep ploughing, shallow ploughing-with-subsoiling, shallow ploughing, and shallow rotary cultivation combined factorially with three manurial treatments on the yields of vegetable crops are described. Each of the five crops in the rotation was grown in each year from i960 to 1962 on a sandy loam at Wellesbourne.

Where a high level of fertility bad been built up by the use of farmyard manure (FYM), yields were subsequently maintained at a high level for a three-year period by the use of NPK fertilizers alone.

Plots which had received either FYM with NPK fertilizers for each crop from 1954 to 1962 (FYM -j- NPK), or FYM with NPK fertilizers from 1954 to 1959 but with NPK only from i960 to 1962 (residual FYM + NPK), gave much higher yields than plots which had received only nitrogenous fertilizers from 1954 to 1959 and NPK fertilizers from 1960 to 1962. The increases in yields from FYM + NPK over those from residual FYM + NPK were small, and significant only for autumn lettuce and leeks.

Although, on average, the differences between the yields from the three ploughing treatments were small (the largest was 10%) some of the differences were significant.

The ploughing treatments gave significantly higher yields of early peas, autumn lettuce, leeks and Brussels sprouts than shallow rotary cultivation ; with early summer cauliflowers, however, only shallow ploughing-with- subsoiling gave a higher yield than shallow rotary cultivation.     

叶面施铁对胡萝卜产量和品质的影响

为了提高胡萝卜产量和品质，以2种根色的胡萝卜为材料，研究叶面喷施不同浓度硫酸亚铁溶液对胡萝卜产量、叶绿素含量及矿质营养的影响。结果表明：施适量浓度的FeSO4·7H2O可以显著提高胡萝卜肉质根合格根率、胡萝卜产量、叶绿素含量及根部铁、锌、镁、钾的含量，其中，“齐头黄”和“红参808”以叶面喷施0.1%的FeSO4·7H2O为最适宜。     

Application of extra sulfur to high-sulfur soils does not increase pungency and related compounds in shortday onions

Sulfur (S) nutrition has a strong influence on onion pungency, and the production of sweet onions in the high-sulfur soil of Texas is a challenge to growers. This study was performed to determine the effects of S applications to fields already having sufficient levels of soil S on pungency and related compounds in four shortday onion cultivars. The onion cultivars ‘Cougar’, ‘Legend’, ‘Texas Early White’, and ‘Texas Grano 1015Y’ were grown in three commercial fields at Edinburg, Mercedes, and Weslaco of the Rio Grande Valley of South Texas with applications of sulfur at 0, 13, and 26 kg S/ha. Pyruvic acid, bulb weight, extractable S in soil and total S in bulb, soluble solids content (SSC), flavor precursor compounds [also called S-alk(en)yl-l-cysteine-sulfoxides (ACSOs)], and total sugars were measured. The pyruvic acid level of onions was not increased by the S applications and showed no significant correlation with soil S levels in any of the cultivars at locations having 30 or 235 ppm S. The SSC, total S in bulbs, total sugars, and total ACSO content also showed no correlation with the S applications and soil S levels. Onion pungency and content of flavor precursor compounds were significantly influenced by cultivar and cultivar × location interaction. We conclude that onion pungency is not increased by application of extra S fertilizer to commercial fields already containing sufficient levels of soil sulfur.     

The Effects of Adding Soluble Salts to the Casing Layer on The Yield and Size of Cultivated Mushrooms

The yield results of six field experiments with bulb onions are presented and it is concluded that : (1) The total yield of ripe bulbs increased with increasing number of plants per sq. ft. until an optimum was reached and thereafter the yield declined.

(2) At the optimum plant densities for total yield the bulbs were too small for normal market purposes but were of a suitable size for pickling whole.

(3) Some varieties of onion would not produce large bulbs even when grown at low plant densities; thus the choice of varieties for ware bulb production is of paramount importance.

(4) The fitting of a mathematic model to the density/yield data showed that if varieties were ranked for yield at anyone plant density this ranking would remain the same at all other plant densities. Absolute yield differences between varieties were, however, greatest at low plant densities.

(5) Decreasing the distance between rows at a given plant density increased the total yield of bulbs. At 7 plants per sq. ft., a density suitable for commercial dry bulb production, reducing the row spacing from 18 in. to 9-12 in. increased yield by 10 to 30%.