Yield formation in Brussels sprouts

Summary

The effects of three planting dates and three plant densities, covering most of the planting dates and densities used in the Netherlands, on yield determining factors of Brussels sprouts (Brassica olerácea var. gemmifera), were studied in field experiments during three seasons. Planting dates were between the end of April and early July. Plant density ranged between 2.7 and 4.4 plants per m². Planting late in the season initially resulted in more leaves being formed, a higher Leaf Area Index and a longer stem. During crop growth this trend was reversed to a lower number of leaves formed, and in two of the three years a lower LAI and stem length when planting was delayed. The effect of plant density on these characteristics was generally either less pronounced than that of planting date or was absent. There was no, or only limited, interaction between the effects of planting date and plant density on these characteristics. The initial rate of dry-matter accumulation after planting was higher after planting late in the season, but the final amount of standing dry matter was reduced by the late planting. Plant density did not influence the final amount of standing dry matter. There was no interaction between the effects of planting date and plant density on dry-matter accumulation. Planting date and plant density hardly influenced the radiation use efficiency. Overall radiation use efficiency was 2.2 g MJ^–1. The time of bud initiation expressed as numbers of days after planting was advanced by delayed planting, but was not influenced by plant density. Planting late in the season decreased the number of buds per plant and in one of the three years also reduced the weight per bud. A decrease in the number of buds per plant due to increased plant density was more than compensated for by the increase in number of plants per hectare. The final number of buds as a percentage of the final number of leaves, was either not, or not consistently, influenced by treatment. Bud dry-matter concentration at final harvest decreased when planting was delayed, but was not influenced by plant density. There was no interaction between the effects of planting date and plant density on bud dry-matter concentration. The dry-matter harvest index of 30–45% was not greatly affected by treatments. To aim for high yields, planting should be as early as field conditions allow.     

Carnation yield patterns: The effects of plant density and planting-date

Carnations, cultivar ‘White Sim’, were planted on 17 January, 12 March, 11 July, 12 September and 7 November, at densities of 12.9, 25.8, 51.7 and 103.3 plants m^?2. For each planting-date, yields within a year from planting were asymptotically related to plant density. The mid-winter plantings gave the highest yields and the July planting the lowest.Yield patterns, derived from a weighted moving average, were affected by both the date and the density of planting. At high density, a major part of the year's yield came from the first flush, accounting for 48% of the total yield in the September planting and 75% in the March planting. At the low density, the first flush was only 26–31% of the year's yield. After the first flush, crop yields were suppressed more at higher densities, especially in the November, January and March plantings. Densities of 25.8 and 51.7 plants m^?2 gave the best continuity of production per unit area, whilst the lowest density gave the best continuity of production per plant.The suppression of flower initiation was related to the amount of light; in November less than 20% of the incident light penetrated the canopy of a high-density September planting. Continuous light did not materially increase the number of shoots per plant that initiated flowers, its greatest effect being to produce earlier initiation.     

The effect of quantum flux density and net photosynthetic rate on morphology and time to flower of hybrid geraniums

Three cultivars of 63-day-old hybrid geraniums (Pelargonium × hortorum Bailey) were grown under high (800–1200 mE m^?2 s^?1), medium (300–600 mE m^?2 s^?1) or low (100–160 mE m^?2 s^?1) quantum flux densities. Plants grown under low light and 25% greater total leaf area but 25% lower dry weight than plants grown under medium or high levels, regardless of cultivar. Time to flower in all cultivars was negatively correlated with quantum flux density, and specific leaf weight and leaf thickness were positively correlated to net photosynthetic rate. ‘Sprinter Scarlet’ and ‘Sooner Red’ had similar correlation coefficients (r) for most relationships, but r values for ‘Ringo’ were generally not as strong. Quantum flux density appears to affect both organogenesis and maturation of the flower.     

Genotype x environment interaction for planting date and plant density effects on yield characters of strawberry

Summary

Three strawberry cultivars (Camarosa, Carisma and Andana) were grown during 1997 and 1998 seasons, at two locations (Cartaya and Moguer) within the area of Huelva (Spain). Three planting dates (11, 21 and 31 October) and three plant densities: low (35.3.25.cm; 50,793 plants ha^±1), medium (30.3.25.cm; 59,259 plants ha^±1) and high (25.3.25.cm; 71,111 plants ha^±1), were evaluated. Environment, genotypic and genotype-environment (G3E) interaction effects were significant in all characters. The Genotype 3 Planting Date (G3PD) interaction was a significant source of variation for all characters except for average fruit weight (AFW). The other interaction factors were not significant for any character. The G3E and G3PD were studied with the additive main effects and multiplication interaction (AMMI) model. The genotypes evaluated responded positively to high plant densities with maximum yield early and late in the season. Therefore, increasing density of planting is an effective crop management strategy to increase the yield characters except AFW. The study of G3PD interaction revealed that an early planting date (planting on 11 October) would give the highest yields.     

Temperature influences nutrient absorption and uptake rates of bananas grown in controlled environments

We explored the influence of temperature on the concentration of nutrients in banana plants, the nutrient uptake rate, apparent root transfer coefficient ($\text{}\text{?}$ga) and the relationship between accumulation of dry matter and nutrient. Young banana plants (Musa (AAA group, Cavendish sub-group) ‘Williams’) were grown at six temperature regimes (17/10–37/30°C) in sunlit growth chambers for 12 weeks.The amount of nutrient absorbed was influenced by the amount of growth made, but the link between the two differed from one element to another. Temperatures less than $\text{29}\text{22°}\text{C}$ reduced the concentration of all elements in the whole plant, except Fe.Temperature influenced the root uptake rate of B 10-fold; K, Na, Ca, Fe and Zn 3–4-fold; and N, P, Mg, Mn, Cu, Cl 1–2-fold. Among the elements the highest recorded rate was 12 mg g^?1 day^?1 for K at $\text{33}\text{26°}\text{C}$. The optimum temperature for nutrient uptake rates differed among the elements. This was accounted for largely by greater growth at those temperatures of organs with high concentration of particular elements.The $\text{}\text{?}$ga (an estimate of efficiency of uptake) of B varied 12-fold among treatments; K, Ca, Mg, Na, Mn, Zn and Cl varied 3–5- fold and N, P, Cu and Fe varied 2–3-fold.The ratio of relative nutrient accumulation rate, R_m, to the relative growth rate, R_w, was most stable across temperatures for N and least stable for B and Na. However, the trend was for $\text{R}{}_{\mathrm{<mtext>m</mtext>}}\text{R}{}_{\mathrm{<mtext>w</mtext>}}$ to increase as temperature rose, indicating an absorption of nutrients greater than might be expected from a change in growth rate as temperature increased, and a decreased efficiency in their utilization for plant growth.     

Conditioning alleviates reduced yield of smaller plugs of ‘Albion’ strawberry (Fragaria X ananassa Duch.) in off-season plasticulture production

The influences of plug size, planting density, and mulch colour on responses to photoperiod and nitrogen conditioning of ‘Albion’ strawberry (Fragaria x ananassa Duch.) plants were evaluated in off-season field production in New Jersey, USA. Three different sized plug plants (7.6 cm square pots, 24-cell plug trays, or 50-cell plug trays) were conditioned with natural days (ND, natural daylength) or long days (LD, natural daylength supplemented with 24 h incandescent radiation) for one week followed by ND plus 100 ppm nitrogen (N) for 4 weeks or LD plus 800 ppm N for 4 weeks. Plants were then established in plasticulture on black, white, or silver mulch. In a second experiment, plug plants (439 cm³) were conditioned with LD and nitrogen then established in plasticulture on black, white, or silver mulch at 3 planting densities (0.46, 0.23, and 0.16 m²?plant^?1 (2, 4, and 6 plants?m^?2)). Fruit were harvested from August through October in both experiments. Conditioning enhanced off-season fall production. White plastic enhanced survival, productivity, and fruit size and larger plugs were more productive than smaller ones. If smaller plugs are desired, conditioning prevents the reduction in yield observed with non-conditioned smaller plugs.     

The response of onions to solar heating,agricultural practices and pink-root disease

Solar heating (solarisation) of the soil, by means of mulching with transparent polyethylene sheets in the hot season, is used for disease control. The effect of soil solarisation, under different agricultural practices, on incidence of pink-root disease caused by Pyrenochaeta terrestris, and on onion yield and quality was investigated. Onions were seeded in beds of non-infested, either non-solarised or solarised, soil and transplanted into growth containers filled with soil either non-infested or infested with the pink-root pathogen. Growth of plants pre-grown in solarised beds was improved as compared to plants originated from non-infested beds. Plants grown in the infested soil suffered considerably, as expressed in leaf number and length, root quantity and bulbing-process. In a field experiment, early sowing resulted in a higher disease incidence than later sowing. Soil solarisation controlled the disease, improved seedling survival and increased yield in most cases. Delay in harvest to 100% falling tops increased yields and reduced percentage of undersized bulbs. At high plant-population density (170 plants m^?2), percentage of small bulbs was higher and rates of double bulbs were lower than at low plant density (90 plants m^?2). Soil solarisation resulted in effective disease control and higher yields and facilitated accurate planning of plant population in the field, extension of the growing-season and higher yields of better quality.     

Gibberellic acid soak treatments for fully-cooled tulips

In attempts to reduce the glasshouse period of fully-cooled 5°C-forced tulips, ‘Apeldoorn’ bulbs were soaked before planting in aerated and non-aerated gibberellic acid (GA₃) solutions for 2–48 h. A 48-h treatment with 250–500 mg l^?1 GA₃ was the most effective, giving a glasshouse period 7–11 days shorter than for untreated bulbs. Soaks for 24 and 48 h caused root emergence, and 48-h soaks caused perianth segment splitting in one experiment. Aerated or non-aerated GA₃ solutions gave similar results. Soaking in water alone gave a smaller increase in earliness. In general, a shortened glasshouse period was associated with shorter whole stem and last internode lengths. In GA₃ treatments, flower losses were lower than for distilled water treated and untreated bulbs. A practical treatment would be a non-aerated soak for 24 h with between 250 and 500 mg l^?1 GA₃.     

Growth and establishment of container-grown London planetrees in response to mulch,root-ball treatment and fertilization

We conducted two experiments to evaluate the impact of cultural treatments on growth and establishment of container-grown London planetrees (Platanus × acerifolia’ Bloodgood’). In both experiments, 48 trees grown in 100 l (#25) black plastic containers were assigned at random to one of three root-ball treatments prior to planting; no treatment (Control), outer 3 cm of roots removed around entire root-ball (Shave), or outer circling roots disentangled from the root-ball (Tease). In Experiment 1, half of the trees were fertilized with 400 g of controlled release fertilizer (15-9-12; N-P₂O₅-K₂O) at planting and the remainder of the trees were not fertilized. In Experiment 2, half of the trees were mulched with an 8 cm deep × 2 m diameter ring of coarse ground pine bark at planting and the remainder of the trees were not mulched. In Experiment 1, fertilization at planting increased SPAD chlorophyll content on two of four measurement dates but did not affect cumulative height or caliper growth after two years. After two growing seasons, root-ball treatments (shaving or teasing) increased root growth outside the original root-ball compared to control trees. Both root-ball treatments also reduced circling roots. In Experiment 2, mulching at planting increased soil moisture and cumulative tree height and diameter growth. Shaving increased new root growth and both root-ball treatments improved root architecture and reduced circling roots. Overall, the study demonstrates that root-ball manipulations can stimulate new root growth and reduce circling roots. Mulch is a valuable aid to conserve soil moisture and increase tree growth. Fertilization at planting provided little benefit in this experiment, which may have been related to a high level of soil fertility at the site or nutrient loading of the trees from nursery culture prior to transplanting.     

The effect of nitrogen,volume of media,plant density and module shape on the growth of asparagus seedlings

There were three experiments in which the seedlings were raised in media contained in plastic cells. In Experiment 1, 150 or 200 mg l^?1 N were applied in factorial combination with cell volumes of 20, 32 or 50 cm³, There were 6 successional harvests. All cells were 7.5 cm deep and cylindrical in shape. Experiment 2 compared these 3 cell volumes at densities of 983, 1532 or 2440 plants per m². Cell diameters restricted the 50-cm³ cell to the 983, and the 32-cm³ cell to the 983 and 1532 plants per m² densities. 200 mg l^?1 N increased shoot growth, but not root growth. This increase in shoot growth was not considered advantageous. Seedling growth increased with increases in cell volume, but there were no responses to changes in plant density. Experiment 3 compared a cell having an inverted pyramid shape with a cylinder. The cylinder, despite holding 20% less media, produced the larger seedlings.     

Effect of temperature and irradiance on vegetative and generative development in Pelargonium × hortorum ‘Radio’

Vegetatively propagated plants of Pelargonium × hortorum ‘Radio’ were grown at 8 combinations of irradiance and temperature levels; 4 or 22 W m^?2 combined with 12, 15, 18 or 21°C. Increase in leaf number, leaf area, shoot and number of inflorescences per plant were all greater at 22 W m^?2 than at 4 W m^?2. At 22 W m^?2, increase in temperature affected leaf number, leaf area and shoot number, but not inflorescence number. However, at 4 W m^?2, number of inflorescences — but not leaf or shoot number — was affected by temperature. When effects of temperature differences were observed, the highest temperature resulted in the greatest number of leaves and shoots and the largest leaf area, but the lowest number of inflorescences per plant. The results indicate that photosynthesis or energy metabolism is of importance to floral initiation in Pelargonium × hortorum.     

Varying evapotranspiration and salinity level of irrigation water influence soil quality and performance of perennial ryegrass (Lolium perenne L.)

Increasing use of recycled water that is often high in salinity warrants further examination of irrigation practices for turfgrass health and salinity management. A study was conducted during 2011–2012 in Riverside, CA to evaluate the response of perennial ryegrass (Lolium perenne L.) ‘SR 4550’ turf to varying quality and quantity of irrigation water. A modified line-source sprinkler irrigation system provided a salinity gradient (EC_w ∼0.6–4.2 dS m⁻¹) in between lines. Irrigation was scheduled in four separate irrigation zones perpendicular to the irrigation lines according to 80, 100, 120, and 140% ET_o. Changes in turf quality (R² = 0.30***), were primarily driven by the number of days that the area had been irrigated with saline water. When data were separated by irrigation amount, both time and water quality accounted for 54% and 46% of the variability (P < 0.001) in quality and cover, respectively at 80% ET_o. A model was created to quantify decline in turf quality in relationship to %ET_o replacement and salinity accumulation in the rootzone (R² = 0.57). Our results suggest that perennial ryegrass requires irrigation scheduling at 140% ET_o, irrigation water quality below EC_w ∼1.7 dS m⁻¹, and EC_e below 3.8 dS m⁻¹ to maintain acceptable quality for 442 d in Riverside, CA.     

Effects of plant density in broccoli on yield and radiation use efficiency

The effects of plant density on broccoli (Brassica oleracea L. var. italica Plenck) commercial characteristics are well determined. However, it is not completely clear how the broccoli plant respond to changes in plant shading as a result of different plant densities. The objective of this experiment was to determine the effect of plant density on intercepted photosynthetically active radiation (PAR), plant architecture, and plant growth and production. “Legacy” broccoli plants were grown in pots in a greenhouse in the seasons of 2002 and 2003 at 2, 4, 6 or 8 plants m⁻² (temperatures: between 10.0 and 16.1 °C, average incident PAR: 12 mol m⁻² day⁻¹). Plant density affected the intercepted and accumulated PAR. There were not effects on the length of the vegetative and reproductive periods, the total and final number of leaves, and the spear diameter and fresh weight. The magnitude and evolution of leaf area (LA) was independent of plant density up to 70 days after transplant (dat). Since then on, LA increased linearly with plant density. The highest intercepted PAR was 70–72% with 6–8 plants m⁻². With the increase in plant density: the erectness of the upper leaves and stem length increased, the extinction coefficient decreased and commercial spear (inflorescence plus a portion of stem 10 cm long) weight decreased (but it was due to the stem portion of the spear and not to the edible portion). On an area basis, the decrease in commercial spear weight with plant density was more than compensated by the higher number of plants. The radiation use efficiency (RUE) increased proportionally with the leaf area index (LAI) up to a LAI of about 3, and then stabilized. The only effect of plant density on dry weight partitioning was to decrease the dry weight allocated to the stem portion of the spear. As plant density increased, and consequently the degree of shading increased, the net assimilation rate (NAR) decreased and the leaf area ratio (LAR) increased. This compensatory change between NAR and LAR, kept the relative growth rate (RGR) for individual plants almost constant.     

The influence of irradiance and external CO2-concentration on photosynthesis of different tomato genotypes

With 4 genotypes of tomato, irradiance and CO₂-response curves of net photosynthesis were analysed by means of curve fitting. Estimated values of the light compensation point I_c showed small but significant differences between the genotypes, the overall value being in the order of 8 W m^?2. The photochemical efficiency (α_n) and the maximum net photosynthesis per unit leaf area basis (P_nm) reached the highest values for ‘F6 IVT’ (13.3 μg CO₂ J^?1 resp. 0.549 mg CO₂ m^?2 s^?1), the lowest value of α_n with ‘Bonabel’ (9.9 μg CO₂ J^?1), and the lowest value of P_nm with ‘PI 114969’ (0.424 mg CO₂ m^?2 s^?1). The CO₂-compensation point (C_c) was relatively high (177–245 mg m^?3). ‘F6 IVT’ demonstrated the highest value of C_c, the lowest carboxylation efficiency and the highest maximum rate of net photosynthesis. The results clearly demonstrate that the latter genotype requires a much higher external CO₂-concentration than the other genotypes in order to exhibit the highest rate of net photosynthesis.     

Response of Lilium longiflorum to ancymidol bulb-dips

Plant height at flowering was reduced in Easter lily (Lilium longiflorum Thunb. cultivar ‘Nellie White’) by momentarily dipping the bulbs in 100 or 264 mg l^?1 solutions of ancymidol [α-cyclopropyl-α-(p-methoxyphenyl)-5-pyrimidinemethanol] prior to planting. The number of flowers was unaffected, and days to flower increased slightly at the highest concentration. This method of application is more effective than soil drench and foliarspray applications.     

The Effects of Nitrogen,Phosphorus, Potassium,Magnesium and Lime in Factorial Combination on the Yields of Glasshouse Tomatoes

Tomato yields and soil analyses from a 3² × 2³ factorial nutritional trial are summarized for six seasons of cropping in heated glasshouse borders. The varieties were Potentate for four seasons, and J168 and Moneymaker (split plot) in the last two seasons. The soil was steamed before planting except in the first and third years.

Deficiencies of nitrogen and phosphorus decreased the yields in five out of six seasons, as also did potassium deficiency in four seasons. Significant positive interactions were found between these three nutrients. The highest level of nitrogen (680–830 lb. N per acre) was favourable when both phosphorus and potassium were at adequate levels in unlimed soil. No yield response was found to potassium in excess of the intermediate level (870 lb. K₂O per acre). The main effect of magnesium was not significant, but a positive phosphorus-magnesium interaction was found for variety Moneymaker.

Lime (carbonate) decreased the yield significantly each season. A significant interaction was found between lime and nitrogen level, the adverse effect of lime occurring at the high and intermediate levels of nitrogen. This effect of lime, and the lime-nitrogen interaction, may be due to induced boron deficiency.     

Growth and photosynthetic characteristics of blueberry (Vaccinium corymbosum cv. Bluecrop) under various shade levels

Blueberry can readily be shaded as a bush type plant, maybe affecting its growth and photosynthesis. Growth and photosynthetic characteristics of ‘Bluecrop’ blueberry grown under various shade levels were investigated to understand acclimation under shade conditions and to determine the optimal light conditions for agricultural purpose. Shade decreased the number of shoots per shrub, but increased shoot length. However, shade did not affect the number of leaves on the main axis. With increasing shade level, leaf length, width and area increased, but leaf thickness decreased. However, there was no obvious tendency in leaf length/width ratio with increasing shade level. Shade leaves had less dense stomata than sun leaves, but stoma was bigger in shade leaves than in sun leaves. With increasing shade level, non-photochemical quenching in blueberry leaves increased and the values were higher at low photosynthetic photon flux densities (PPFDs) in shade leaves than in sun leaves, resulting in the decreases in quantum yield, electron transport rate and net CO₂ assimilation rate (A_n). The maximum A_n at 31, 60, 73 and 83% shade levels was 11.8, 11.0, 8.4 and 7.5 μmol m⁻² s⁻¹, respectively. Following the slight decrease up to 100 μmol m⁻² s⁻¹ PPFD, stomatal conductance (g_s) linearly increased up to 600 μmol m⁻² s⁻¹ PPFD and became saturated at all shade levels. The leaves of the shrubs grown under the 83% shade level had a significantly lower g_s as compared to the leaves of the shrubs grown under the 31, 60 and 73% shade levels. Transpiration rate (E) linearly increased up to 600 μmol m⁻² s⁻¹ PPFD and was saturated at the 73 and 83% shade levels. However, E increased linearly at both 31 and 60% shade levels with increasing PPFD. The reproductive growth characteristics such as number of flowers, fruit set rate per flower bud and fruit yield also significantly decreased with increasing shade level. For agricultural purpose, therefore, shade level above approximately 60% of full sunlight must be avoided for optimal photosynthesis and growth of the ‘Bluecrop’ blueberry.     

Influence of planting geometry on growth,yield and quality of rainfed garlic (Allium sativum L.) cultivated under Mediterranean conditions

Summary

The establishment of the optimum plant population has been shown to be one of the most crucial determinants of the marketable yield of bulbous crops. This study was conducted to determine the best plant arrangements for maximum yields and maximum bulb quality in rainfed garlic (Allium sativum L.) grown under Mediterranean conditions. The effects of row width and plant spacing on the yield and quality of the two cvs. Morado de Pedroneras and Germidour, were investigated on Córdoba, Spain, in Vertisol Chromoxerert soil. In 1987–1988, a wet growing season, higher yields and higher bulb quality were obtained than in 1988–1989; cv. Germidour yielded more per unit of land area of higher quality bulbs during both seasons. Narrow row width and/or narrow plant spacing resulted in higher values of dry matter, LAI, LAD, CGR and yield, whereas wide row spacing and/or wide plant spacing resulted in higher ware-sized bulb yield. LAD was closely related to yield (r² = 0.96**) and total dry matter (r² = 0.90**). Mean leaf surface was affected by plant density and climatic conditions and showed a high positive relationship (r² = 0.90**) with the percentage of Extra grade of bulbs (>50 mm). As a result of this study, a row width of 45–60 cm with plant spacing of 12–16 cm is recommended for cv. Germidour and 45 × 16 cm for cv. Morado, to maximize the proportion of high-quality yield under Mediterranean rainfed cropping systems.     

The effect of planting date and plant density on nitrogen uptake and nitrogen harvest by Brussels sprouts

Summary

Single and combined effects of three planting dates and three plant densities on nitrogen uptake and nitrogen harvest by Brussels sprouts (Brassica olerácea var. gemmifera) were studied in field experiments. The total amount of nitrogen taken up by the crop at harvest ranged between 220 and 325 kg ha^–1. Although final crop dry matter decreased, total nitrogen uptake was not lower when planting was delayed. This resulted in increased nitrogen concentrations both in the total crop and in the harvested product. Forty to fifty per cent of the nitrogen taken up by the harvest was removed from the field with the product. Within the range of 2.7 to 4.4 plants per m², plant density had no effect on final nitrogen uptake nor on the amount of nitrogen harvested with the product. The results indicate that nitrogen fertilizer recommendations should take planting date into account, because with delayed planting less dry matter will be accumulated with a corresponding lower nitrogen requirement. There was no interaction of effects of planting date and plant density on nitrogen uptake.     

Effect of temperature,daylength and light intensity on growth and development of Dipladenia sanderi Hemsl. ‘Rosea’

Dipladenia sanderi Hemsl. ‘Rosea’ (syn.: Mandevilla sanderi (Hemsl.) Woodson ‘Rosea’) was grown in a glasshouse at 12, 15, 18 and 21°C, daylengths of 8 or 20 h, natural daylight, and natural daylight supplemented with cool-white fluorescent lamps (10 W m^?2).Time from propagation to unfolded flower decreased with increasing temperature, and at 12°C there were relatively few flowers in the inflorescences. The time to flower opening was not influenced by daylength, but with 20 h there were more buds in the first developed inflorescence and the petals were larger than with 8 h. In addition, the vegetative growth was favoured by 20 h. Supplementary lighting shortened the developmental time to unfolded flower, but the flowers were smaller than in natural light only.The growth and development varied according to the time of year. Dipladenia was able to bloom all year round, except in January and February. The low light intensity in November and December probably made it impossible for the buds to develop into flowers in January and February.