The effects of nutrient solution sterilization on the growth and yield of hydroponically grown lettuce

Two methods of removing bacteria from hydroponic nutrient solution [ultraviolet (UV) radiation and submicronic filter] were evaluated for efficiency and for their effects on lettuce (Lactuca sativa L.) production. Both methods were effective in removing bacteria; but, at high intensity, the ultraviolet sterilizer significantly inhibited the production of plants grown in the treated solution. Bacterial removal by lower intensity UV or a submicronic filter seemed to promote plant growth slightly, but showed no consistent, statistically significant effect.     

Effects of copper deficiency and liming on the yield,quality and copper status of tomatoes,lettuce and cucumbers grown in peat

Tomatoes, lettuce and cucumbers, grown in beds of peat, received 3 levels of copper sulphate (0, 0.5 and 5 g/m²) in factorial combination with 2 rates of liming (average pH values 6.5 and 6.9). Omission of copper resulted in copper deficiency and decreased the yield of tomatoes, lettuce and cucumbers by 11% (P < 0.01), 53% (P < 0.001) and 48% (P < 0.001), respectively. In addition, this deficiency increased the proportion of unmarketable lettuce six-fold (P < 0.001) and that of poorly developed cucumbers by 67% (P < 0.05), but had no effect on the proportion of unevenly ripened tomatoes. Heavy liming (pH 6.9) reduced the yield of lettuce (14%; P < 0.01), but had no effect on quality throughout the trial. Although lettuce and cucumber leaves from the intermediate copper treatment contained only 2 μg/g Cu, the yield and quality of the produce were only slightly, and not significantly, inferior to those obtained at an adequate level of copper (> 7 μg/g).     

不同播种期对南京地区韭葱采种的影响

为探讨南京地区韭葱采种技术问题,以美国韭葱为供试材料,研究不同播期对韭葱生长、发育、种子产量和质量的影响。结果表明,不同播期对韭葱生长发育有一定影响。韭葱8月中旬至9月上旬播种,生长旺盛,植株高度、假茎粗度、开展度、叶片数量等优于9月中旬播种;采种产量,9月上旬、8月下旬播种显著优于8月上旬、9月中旬播种,其中9月上旬播种最高为每667 m2132.9 kg。在南京地区韭葱8月中旬至9月中旬播种,均能够正常生长、采种;韭葱采种的适宜播期为8月下旬至9月上旬。     

The effect of trickle irrigation,misting and row position on the incidence of tipburn of field lettuce

The effect of trickle irrigation, with and without additional applications of night mist, just before maturity on the incidence and severity of tipburn in field lettuce was investigated. The mean incidence of tipburn for all treatments was much higher (84%) on the outer 2 rows of beds than on the inner 2 rows (47%). On the outer rows irrigation and misting had virtually no effect on tipburn, whereas on the inner rows irrigation reduced it from 72% (in control plants) to 39%, misting to 63% and misting + irrigation to 16%. It is believed that the combination of night misting and trickle irrigation of inner rows resulted in conditions conductive to root-pressure flow which translocated calcium ions to heart leaves of lettuce plants, thereby reducing tipburn injury. It is suggested that the increased severity and incidence of tipburn in the outer rows could have resulted from soil compaction in wheelings which would reduce root growth, soil aeration and root pressure.     

Comparison of sub-irrigation and overhead irrigation of tomato and lettuce seedlings

Summary

Overhead irrigation is a common irrigation practice in nurseries, yet it can be wasteful of water and nutrients. We compared the water use, fertilizer use and growth of ‘Top Gun’ lettuce (Lactuca sativa L.) and ‘Grosse Lisse’ tomato (Lycopersicon esculentum Mill.) seedlings in sub and overhead irrigation systems. Five rates of controlled release fertilizer were used – 0.625, 1.25, 2.5, 5 and 10 kg m^–3. Sub-irrigation used 86% less water than overhead irrigation. Irrigation type had a significant effect on some growth measurements by final harvest, 43 d after sowing. The sub-irrigated lettuce seedlings were significantly taller. The overhead irrigated lettuce seedlings had a higher dry weight and more leaves. The sub-irrigated tomato seedlings were taller, had longer leaves, a larger leaf area and more leaves. Increasing levels of controlled release fertilizer produced quadratic type responses over time for shoot dry weight, with 10 kg m^–3 producing tomato and lettuce transplants with a higher biomass in a shorter time than lower levels of fertilizer.     

Regulated deficit irrigation effects on yield,nut quality and water-use efficiency of mature pistachio trees

Summary

Regulated deficit irrigation (RDI) was evaluated on deep rooted, mature pistachio trees grown under high evaporative demand in the low rainfall southern San Joaquin Valley of California. The focus of this work was to assess the impact of deficit irrigation during various parts of the season with the goal of determining which period was most stress tolerant in terms of nut production. Pistachio nuts have a unique fruit growth pattern in which rapid kernel growth does not begin until about six weeks after full shell size has been attained. Our hypothesis was that irrigation could be reduced during this period with limited negative effects on production. The season was divided into three preharvest periods: leafout to full shell expansion (Stage 1), full shell expansion to the onset of rapid kernel growth (Stage 2), and rapid kernel growth to harvest (Stage 3). Water deprivation during Stage 1 applied 7.2% less water than the near-fully irrigated Control without any yield loss, based on mean values for the last “on” and “off” alternate bearing years of this study. Shell splitting (endocarp dehiscence) at harvest (a positive impact) was significantly higher (10.4% relative to the Control) but this was offset by a nut weight reduced by 9.4%. Stage 3 water deprivation (53% less applied water than the Control) significantly reduced nut size, shell splitting, mechanical nut removal by tree shaking, and yield, while increasing kernel blanking and abortion. Postharvest water deprivation (5.0% less applied water than the Control) had no significant negative effects on yield components. Six irrigation regimes that applied water at various rates were used to investigate Stage 2 behaviour. While there were no significant differences in yield components among these regimes, the best production occurred with deficit irrigation during Stage 2 at 50% of near-potential ETc during Stage 2 and 25% of near-potential ETc after harvest. This RDI regime saved about 180 mm of water (23.2% of the Control) and water use efficiency was significantly higher (4.69 versus 3.61 kg marketable fruit per mm water, for this RDI regime and the Control, respectively). We believe RDI during Stage 2 and postharvest is a viable irrigation strategy to save water while maintaining top yields of high quality pistachio nuts. Further work is needed to determine if the improved shell splitting harvest that occurred with Stage 1 stress can be exploited to improve grower profits.     

Effects of watering on the yield,quality and composition of tomatoes grown in bags of peat

Two crops of tomatoes, grown in bags of peat, were supplied with 60,80,100 and 120% of the water requirement estimated from solar radiation integrals for 12 weeks after planting. Restricting water to 60% and 80% of the requirement controlled vegetative vigour but reduced final yield by about 20% and 4% respectively. These decreases were mainly because of a reduction in fruit size rather than number. Overwatering had little effect on yield but caused Mn deficiency. As restricted watering reduced the water content of the fruit, so.the dry matter, sugar, acid and potassium concentrations in the fresh material increased; this was particularly marked in plots receiving only 60% of the water requirement. The response to the treatments disappeared 4-5 weeks after they were discontinued. Retention of six extra leaves in one crop had no effect on yield. The data suggest that watering should be restricted to 80% or less of the estimated requirement in order to achieve a significant improvement in the flavour components of the fruit.     

腐殖酸水溶性肥料对莴苣产量和效益的影响

为了解施用腐殖酸水溶性肥料对莴苣产量和效益的影响,以便在生产上推广应用,笔者在莴苣生长期进行了施用试验。结果表明,在莴苣旺盛生长期和茎部肥大期,每667m2用腐殖酸水溶性肥料100mL加水50kg进行叶面喷施,能够使莴苣产量提高170kg以上,增产率在7%以上,667m2可增加收入200元,投入产出比达到1∶10。莴苣喷施该肥料,技术简单实用,增产增效明显,建议在生产上推广应用。     

Seasonal effects on the cropping-cycle of lettuce in glass-houses during the winter

Current information about the duration of the lettuce cropping-cycles in glasshouses during the winter is presented as linear functions which provide a simple model for crop planning. The data are also plotted against the date in the middle of each cropping-period, in order to show as accurately as possible the effect of growing-conditions on the duration of the cropping-cycle. Plotting the data in this way is based on the concept that the cropping-cycle depends mainly on seasonal radiation, presented by two-sided linear functions with a maximum value around the shortest day (21 December). The amount of radiation appears to be the dominant factor which determines the length of the cropping-cycle.     

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.     

Effects of ages of plug transplants and planting depths on the growth and yield of sweetpotato

Sweetpotato [Ipomoea batatas (L.) Lam. cv. Beniazuma] plug transplants produced from single node leafy cuttings under artificial light in a closed-type growth chamber were planted with roots and substrate of 11- and 15-day old (ca. two to three unfolded leaves with 0.08 m shoot length and three to four unfolded leaves with 0.11 m shoot length, respectively). The plug transplants of both the 11- and 15-day old were planted with one and three nodes depth (ca. 4 and 25 mm deep, respectively) inside the soil ridges (called one- and three-node depth, respectively, hereafter). The conventional vine cuttings (ca. 0.3 m long with seven to eight unfolded leaves) without roots were planted as Control treatment to compare the growth and yield of sweetpotato with each of the treatments of plug transplant. The main objectives of the study were to see the effects of ages of plug transplants and depths of planting for greater growth and yield of sweetpotato in the field. The yield of storage roots 115 days after planting in the field was 33 t ha⁻¹ when using 15-day old plug transplants planted with three-node depth and was 10 t ha⁻¹ greater than that in the Control. The mean storage root length was about 259 mm when using 11-day old plug transplants planted with three-node depth and was 33 mm greater than that in the Control. The mean diameter of storage roots was 70 mm when using 11- and 15-day old plug transplants planted with one-node depth and was 21 mm greater than that in the Control. The plug transplants planted either 11- or 15-day old showed greater overall performances than those of the conventional cuttings. The plug transplants planted with three-node depth showed greater performances than did the plug transplants planted with one-node depth.     

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

Summary

The 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.     

Effect of irrigation frequency on cashew nut yield in Northeast Brazil

The study was carried out in Ceará, Brazil, with the goal of evaluating the response of three dwarf cashew clones to different irrigation frequencies. Cashew trees were evaluated during seven consecutive seasons, from the 2nd to the 8th year after planting. Four irrigation treatments were used: no irrigation, and irrigation when accumulated evaporation on a class “A” pan equaled 10 mm (T10), 30 mm (T30), and 50 mm (T50). The sub plot treatments were three cashew clones (CCP 09, CCP 76, and CCP 1001). Seasonal irrigation rates were the same for all irrigated treatments, and ranged from 400 to 500 mm per year for fully developed plants (6–8 years old). Response to irrigation varied among cashew genotypes. Irrigation had a significant effect (P < 0.05) on nut yield of cashew clones CCP 76 and CCP 09. The highest nut yield was obtained with cashew clone CCP 09, irrigated when accumulated pan evaporation reached 10 mm. Cashew trees trended to alternate years of high nut yield and years of low yield, even when irrigation was applied. Irrigation did not influence nut weight of clones CCP 76 and CCP 09.     

钾锌营养对水培生菜生长、产量和品质的影响

通过增施钾肥、锌肥和钾锌同增,研究钾锌肥对生菜生长、产量和品质的影响,以期为生菜优质、高效生产模式下的施肥管理提供理论支撑。结果表明,钾、锌肥对生菜生长均有促进作用,钾锌同增效果最显著,较对照株高显著增长23.71%;钾肥和锌肥均可提高生菜可溶性蛋白和可溶性糖含量,钾锌同增处理的可溶性蛋白和可溶性糖含量较对照分别增长23.82%、115.54%;但维生素C含量会因为钾水平过高而降低,对照较增施钾肥处理显著增长68.30%,锌肥对生菜维生素C含量有促进作用;钾、锌肥均可提高生菜硝酸还原酶活性,降低硝酸盐含量,且钾锌肥互作的协同效果更佳,较对照高42.78%;钾、锌肥通过影响生菜叶绿素的合成进而影响生菜产量,钾锌同增处理生菜产量最高,较对照高77.93%,其次是增钾处理,对照处理产量最低。     

Weed control and yield response of soil solarization with different plastic films in lettuce

Phase out of most chemicals available for weed management renewed the interest in soil solarization as a technically effective and environmentally safe practice for lettuce weed control in hot summer areas. Properties of solarizing films and lettuce crop system may considerably affect weed control and yield response of soil solarization. Different solarizing films, including low-density polyethylene, ethylene-vinyl acetate copolymer, low-density polyethylene–ethylene-vinyl acetate coextruded and a biodegradable corn starch-based film, were evaluated in 2003 and 2004 for weed control and lettuce yield response under field and greenhouse conditions in Southern Italy. Soil solarization strongly reduced weed density and biomass in both greenhouse and in the field, with no significant differences among the tested plastic films. Most annual weeds were completely controlled by soil solarization, except amaranth, Amaranthus spp., in soil solarized with biodegradable film in the field. Emergence of mediterranean sweetclover, Melilotus sulcatus, was stimulated by soil solarization in greenhouse. In the field, Cyprus vetch, Lathyrus ochrus, was found in solarized plots though absent in untreated soil. Perennial weeds were not affected by soil solarization, except a strong control of canadian thistle, Cirsium arvense, in the field. Lettuce yield resulted significantly higher in solarized soil than in control plots, with no significant differences among the solarizing materials. All tested materials proved to be technically effective for soil solarization in lettuce, though low resistance and short durability of biodegradable film may suggest its application mainly to soil solarization in greenhouse or in organic systems.     

Comparative effects of partial root-zone irrigation and deficit irrigation on phosphorus uptake in tomato plants

Summary

The comparative effects of partial root-zone irrigation (PRI) and deficit irrigation (DI) on phosphorus (P) uptake in tomato (Lycopersicon esculentum Mill.) plants were investigated in a split-root pot experiment. The results showed that PRI treatment improved water-use efficiency (WUE) compared to the DI treatment. PRI-treated plants accumulated significantly higher amounts of P in their shoots than DI plants under organic maize straw N fertilisation, whereas similar levels of shoot P accumulation were observed under mineral N fertilisation. Thus, the form of N fertiliser, and thereby the different plant N status, affected the accumulation of P in shoots, as reflected by a higher plant N:P ratio following mineral N fertilisation than after organic N fertilisation. Compared to the DI treatment, PRI significantly increased both the physiological and agronomic efficiencies of P-use under mineral N fertilisation, while similar physiological and agronomic P-use efficiencies were found between the two irrigation treatments with organic N fertilisation. PRI-induced drying and wetting processes might have influenced the bio-availability of soil P, as the concentrations of bio-available P in both bulk and rhizosphere soils were increased compared with the DI treatment under both forms of N fertilisation. It is suggested that a relatively high soil water content in the wet zone of the PRI treatment should be maintained in order to facilitate nutrient (i.e., N and P) transport from the bulk soil to the root surface, thereby enhancing nutrient uptake by the roots.     

Modification of yield and chlorophyll content in leaf lettuce by HPS radiation and nitrogen treatments

This study evaluated the potential of high photosynthetic photon flux (PPF) from high-pressure sodium (HPS) lamps, alone or in combination with metal halide (MH) plus quartz iodide (QI) incandescent lamps, to support lettuce growth, with or without N supplementation. Varying exposures to radiation from combined HPS, MH, and QI lamps influenced dry weight gain and photosynthetic pigment content of hydroponically grown Black-Seeded Simpson' lettuce (Lactuca sativa L.) seedlings. Cumulative leaf dry weight declined with increasing exposure, up to 20 hours per day, to 660 micromoles m-2 s-1 of photosynthetically active radiation (PAR) from HPS lamps concomitant with constant 20 hours per day of 400 micromoles m-2 s-1 from MH + QI lamps. Leaves progressively yellowed with increasing exposure to radiation from the three-lamp combination, corresponding to lower specific chlorophyll content but not to specific carotenoid content. Lettuce grown under 20-hour photoperiods of 400, 473, or 668 micromoles m-2 s-1 from HPS radiation alone had the highest leaf dry weight at a PPF of 473 micromoles m-2 s-1. Chlorophyll, but not carotenoid specific content, decreased with each incremental increase in PPF from HPS lamps. Doubling the level of N in nutrient solution and supplying it as a combination of NH4+ and NO3- partially ameliorated adverse effects of high PPF on growth and pigment content relative to treatments using single-strength N as NO3-.     

The effects of pre-sowing seed treatments on the germination and emergence of lettuce seeds at high salt concentrations

Radicle emergence in lettuce seeds cultivar ‘Hilde’ was reduced by NH₄NO₃ above 8×10^?2M, while radicle extension was inhibited by 8×10^?2M NH₄NO₃ and no seedlings emerged. Inhibition of radicle emergence by 8 and 16×10^?2M NH₄NO₃ was prevented by soaking seeds for 4 h before sowing in a mixture of $\text{GA}{}_{\mathrm{<mtext>4</mtext><mtext>7</mtext>}}$ and kinetin+phosphate buffer, and was partially prevented by soaking them for 4 h before sowing in phosphate buffer. These treatments did not prevent inhibition of radicle emergence by 32×10^?2M NH₄NO₃, but seeds soaked in growth regulators or phosphate buffer before sowing and taken from this NH₄NO₃ solution after 7 days and washed to remove excess salt gave 45–52% germination compared with 12 % for untreated seeds. Pre-treatment of the seeds did not prevent the inhibitory effect of NH₄NO₃ on radicle extension. In field experiments seeds treated with growth regulators + phosphate buffer or phosphate buffer alone gave a higher final percentage emergence from soils given 125 kg N/ha than did untreated seeds.     

灌溉方式和灌水量对梨产量和水分利用效率的影响

连续2年对8～9年生黄冠梨树采用不同灌溉方式和灌水量的试验,结果表明,树盘1/2区域交替灌溉较常规灌溉用水量减少2/5,其蒸腾速率显著低于常规灌溉,而水分利用效率显著高于常规灌溉,2者之间的光合速率、产量和单果重不存在显著差异。树盘1/2区域固定灌溉的水分利用效率介于2者之间,但产量和单果重与2者差异显著。     

Water relations and yield of lysimeter-grown strawberries under limited irrigation

The effects of partial root-zone drying (PRD), as compared to deficit irrigation (DI) and full irrigation (FI), on strawberry (cv. Honeoye) berry yield, yield components and irrigation water use efficiency (WUE_I) were investigated in a field lysimeter under an automatic rain-out shelter. The irrigation treatments were imposed from the beginning of flowering to the end of fruit maturity. In FI the whole root zone was irrigated every second day to field capacity viz. volumetric soil water content (θ) of 20%; while in DI and PRD 60% water of FI was irrigated to either the whole or one-half of the root system, respectively, at each irrigation event. In PRD, irrigation was shifted from one side to the other side of the plants when θ of the drying side had decreased to 8–11%. Compared to FI plants, leaf water potential was significantly lower in DI and PRD plants in 3 out of 10 measurement occasions, while stomatal conductance was similar among the three treatments. Leaf area, fresh berry yield (FY), individual berry fresh weight, berry water content, and berry dry weight (DW) were significantly lower in DI and PRD plants than those of FI plants; whereas the total number of berry per plant was similar among treatments. Compared with FI, the DI and PRD treatments saved 40% of irrigation water, and this led to a 28 and 50% increase of WUE_I based on berry FY and DW, respectively, for both DI and PRD. Conclusively, under the conditions of this study PRD had no advantage compared to DI in terms of berry yield and WUE_I. DI and PRD similarly decreased berry yield and yield components and thus cannot be recommended under similar conditions.