Seedling Tray Research Articles

Study on the Optimum Planting Density of Pot Seedling for Mid-Late Maturing Rice Variety in Wheat-Rice Double Cropping System in Honam Plain Area

This experiment was carried out to determine the optimum planting density for rice pot seedling cultivation in wheat-rice double cropping system in Honam plain area. A mid-late maturing rice variety 'Chinnong' was raised in pot seedling tray and conventional tray for 30 days, and then transplanted on June 25 in 2012 and 2013. Four different planting densities (15.2, 18.9, 21.6, and 25.3 hills per m 2 ) in pot seedlings were applied as treatment. Conventional tray seedling was implicated as control at a single planting density of 27.8 hills per m 2 . In this experiment, the number of effective tillers was increased as planting density increasing, but stem diameter was decreased. Pot seedling showed higher stem diameter and effective tillers than the control. Heading dates of pot seedling plots were not significantly different between the planting densities but 2 days faster than the control. Culm length, number of panicles, panicle length, and ripening grain ratio were higher in pot seedling compared to the control, but 1000-grain weight showed no significant difference. Milled rice yields in pot seedlings ranged from 5.19 to 5.43 t ha -1 , and the highest yield was observed in 21.6 hills per m 2 . Head rice ratios in pot seedlings and the controls were not significantly different. Above results on planting density of rice pot seedling cultivation would be applicable to wheat-rice double cropping and also to late transplanting cultivation of rice single cropping.

Design and test of tray-seedling sorting transplanter

In order to improve the automatic sorting and transplanting of tray-seedling and reduce labors strength, a new sorting transplanter was designed. According to the feature of normal seedling tray and manual grading method, the mechanical sorting procedure was defined. The key parts of sorting transplanter are as follows: an efficient transfer mechanism with aerodynamic buffer, a seedling identifying and measuring unit based on linear-structured vision, the extendible multi-grasper with wireless technology and the system controller. The experiments were conducted and showed that the transplanting success rate was 90.0% on the tray of 6×12 holes under the speed of 700 cycles per hour. The vision unit’s failed identifying rate for the superior pepper seedlings on five different trays was less than 10%, and the measurement error of seedling height was about 5 mm. Keywords: transplanter, tray seedling sorting, grasper, machine vision, wireless technology DOI: 10.3965/j.ijabe.20150802.1459

Suppressive effects of palisade grass (Brachiaria brizantha) on Pratylenchus coffeae

The suppressive effects of palisade grass (Brachiaria brizantha) cv. MG5 on Pratylenchus coffeae were tested in pot and seedling tray experiments and under field conditions. In pot tests, four isolates of P. coffeae were tested by inoculating 500 mixed life stages of each isolate on 5- or 7-week-old palisade grass plants. The nematode number in palisade grass was significantly lower than in susceptible cucumber in all isolates and below 20% of the inoculated level 69-86 days after inoculation. In seedling tray tests, the number of eggs and adults + juveniles in palisade grass roots was examined 5-25 days after inoculation (dai) of 200 mixed life stages of an isolate of P. coffeae to a 3-week-old seedling. The number of adults + juveniles in palisade grass roots was not statistically different from sorghum and black oat 5 and 10 dai, while the number of eggs and adults + juveniles was significantly lower than these two plants 20 and 25 dai. In field plot tests, palisade grass was cultivated for approximately 4 months in 2011 and 2012. The P. coffeae density after palisade grass cultivation was significantly lower than that after bare fallow in 2011, whereas the nematode density was not significantly different between these two treatments in 2012. Rates of lesions on sweet potatoes cultivated after growing palisade grass were significantly lower than those after growing sorghum or guinea grass, but not significantly different from that after fallow. These results indicated that the cultivation of palisade grass cv. MG5 has a nematode suppressive effect that is comparable to fallow treatments.

개량상자를 위한 못자리 유형과 상토에 따른 적정 물관리 방법 연구

개량상자를 위한 못자리 유형과 상토에 따른 적정 물관리 방법 연구

Systemic application of chlorantraniliprole to cabbage transplants for control of foliar-feeding lepidopteran pests

The diamide insecticide chlorantraniliprole is registered for control of lepidopteran pests in cabbage (Brassica oleracea L.). Taking advantage of its root-uptake systemic properties, chlorantraniliprole is labeled for use with a variety of soil application methods in different countries, depending on pests and local practices. We investigated the efficacy of different cabbage transplant application methods using a leaf consumption bioassay. In the laboratory, we compared different transplant water volumes, characterized the effect of transplant plug size when the insecticide is applied by drenching or soaking the seedling tray, and determined the effect of different soil types. At three field sites, we compared the efficacy of chlorantraniliprole applied in transplant water or as a tray drench or tray soak treatment. In the laboratory, transplant water volume did not affect the level or duration of Trichoplusia ni (Hübner) mortality caused by chlorantraniliprole. When seedling trays were drenched with insecticide solution, transplant plug size did not affect mortality, but when trays were soaked with an equivalent volume of solution, mortality was higher with small plugs. Transplanting plugs treated by transplant water, drench or soak into different soil types did not affect mortality caused by chlorantraniliprole. In the field, transplant water application was the most effective method at all three locations. Tray soak was the most variable application method. Different application methods can be used to take advantage of the systemic characteristics of chlorantraniliprole. Among the methods tested, transplant water and tray drench resulted in more consistent mortality under variable field conditions.

EFECTO DE UN BIORREGULADOR A BASE DE AUXINAS SOBRE EL CRECIMIENTO DE PLANTINES DE TOMATE

Production of tomato seedlings in trays has increased in recent years because protecting the root system in a ball reduces transplant shock, resulting in a higher plant survival rate and thus avoiding the need to replant. Greater root development favors establishment in the field because it promotes water and nutrient uptake. Since root production can be promoted by auxin action, the aim of this study was to evaluate the effect of an auxin-based bioregulator on the growth of tomato seedlings in trays. The trial was conducted in a commercial nursery in San Juan, Argentina. The AC 55 tomato cultivar was used. Trays with 126 cells, 36 cm3 per cell, were used. The bioregulator was a commercial formulation containing 0.12 % indole butyric acid and 0.004 % forchlorfenuron. Four concentrations of the product (1, 3, 5 and 7 ml·liter-1) and a control were tested in a completely randomized design with 5 treatments and 4 replicates. Samples were taken at 26, 33, 40 and 47 days after sowing. The variables measured were root dry weight (RDW), aerial dry weight (ADW), stem length (SL), number of leaves larger than 1 cm (NL) and third leaf length (LL). Higher doses increased RDW by 36-39 % compared to the control. The regression between root dry weight and applied dose indicates there could be a response to higher doses. No effect on growth in the aerial part of the plant was observed.

Large-scale screening of rice accessions to evaluate resistance to bakanae disease

Bakanae disease is an important fungal disease in the world. No rice (Oryza sativa L.) varieties have been found to be completely resistant to this disease. To facilitate accurate, uniform and simultaneous screening of many rice accessions, we developed an inoculation method for microconidia of Fusarium fujikuroi using a tissue embedding cassette and seedling tray. Standards for evaluating the inoculated rice seedlings as healthy or unhealthy were also established. The method was fast and reproducible for accurately evaluating resistance to bakanae disease in rice.

Development of System Rice Intensification (SRI) Paddy Transplanter

The System of Rice Intensification (SRI) practices have been developed in order to increase the production and quality of rice. Based on SRI practices the rice seedlings are transplanted at the young ages, 15 days old with just 2 leaves and carefully planting of just one seedling per hill and space the hills optimally widely in a square pattern of 25×25 cm for better usage of water, sunlight, minerals, space, nutrient, weeding and pest management within shallow depth (1-2 cm) in the moist soil condition. The existing method of mechanical transplanting of paddy which planted between 5 and 8 seedlings per stand is claimed to be inefficient to produce higher yield. From the survey that was carried out, most farmers are looking forward to single-planting translators as it is impossible to do it manually. Modifications have to be carried out on the planting claw (kuku kambing) so that it will only catch one seedling at a time, redesign the seedling tray to allow the SRI transplanter to catch one seedling at a time and determine the best soil condition suitable for the SRI practices. No doubt that the new develop transplanter for SRI will be the future machines for the farmers in Malaysia. Evidence have shown that the SRI practices in paddy cultivation has resulted in the increase in yield as well as superior quality paddy because of its shorter crop cycle, less need for seeds and fertilizer, less chaffy grain because of higher percentage grain filling, little or no lodging from wind or rain and higher head rice recovery rate, so more milled rice from a given amount of paddy and reduced labour demand while boosting productivity. The most important factors that influence the performance are soil moisture content, system of raising seedlings in nursery, degree of land labelling and finally the size of planting claw.

Reloading mechanized tree planting devices faster using a seedling tray carousel

On Nordic clearcuts, today’s tree planting machines produce high-quality but costly regenerations. Much of this high cost is attributable to the planting machines’ low productivity. One promising way of raising productivity is to lessen the time spent manually reloading seedlings onto the carousels of crane-mounted planting devices. Using MagMat, a carousel test-rig designed by engineering students, we studied how much faster tray-wise seedling reloading is on the Bracke Planter compared to reloading with today’s seedling-wise-loaded carousel. The MagMat test-rig held eight Hiko cultivation trays from which seedlings were deplugged individually and dropped into the planting tube. The time study confirmed that seedling reloading was on average twice as fast with MagMat compared to today’s seedling carousel, thereby increasing assumed planting machine productivity by 8–9% depending on the planting device used. MagMat’s cost-efficiency was analysed to be particularly reliant on its added investment cost, mechanical availability and how quickly trays can be switched automatically. Nevertheless, MagMat’s field performance illustrated the overall potential of tray-wise loading compared to piecewise seedling loading for increasing the productivity of crane-mounted planting devices. Also, deplugging proved to be a reliable method of extracting seedlings from the rigid, copper-painted Hiko cultivation trays even when performed at the excavator’s boom-tip during mounding work. We conclude that, rather than piecewise seedling loading, tray-wise loading combined with deplugging seedlings from suitable cultivation trays is a reliable and much more time-efficient method to feed seedlings on probably any type of tree planting machine.

Protected cultivation as an option of livelihood in mountain region of central Himalaya, India

Protected farming is an alternative new technique for seasonal and off-seasonal vegetable cultivation, particularly in high-altitude region, and can be successfully employed for niche areas of agriculture. Experimentation on vegetable crops under protected conditions was carried out to see the feasibility of their farming at different altitudes in the central Himalayan region. For evaluating the suitable conditions required for the cultivation of vegetables, three treatments, viz., polyhouse, shade net, and plastic-mulch, were selected in comparison to open condition at both the altitudes. Capacity building through organizing training program was adopted for demonstration and dissemination of this technology to rural farmers of the region. The yield of selected vegetables was found to be significantly (P < 0.05) high under protected cultivation, and the productivity of vegetables has been observed to increase from 15.85% to 932.20% as compared to that in open field condition at both the altitudes. As a result of capacity building, a number of households (78) at high and low altitudes (41) adopted seasonal and off-seasonal vegetable cultivation through protected cultivation technology at various levels. This is the first study of its kind, and in the present case, we demonstrated that protected cultivation is an alternative and efficient technology for seasonal and off-seasonal vegetable cultivation, particularly at high-altitude region. The production of vegetable seedling is gradually changing from open field nurseries to protected raised bed or seedling tray production after obtaining technical know-how. It is hoped that the improved capacities of local farmers would help in spreading this technology through adoption of protected cultivation in the central Himalaya and other high-altitude region of other countries having similar environmental and socio-economic conditions.

Transplanting Path Planning and Motion Functions Research of the High-Speed Tray Seedling Transplanting Robot

High-speed tray seedling transplanting robot was developed which used two-DOF parallel mechanism as transplanting mechanism, and pneumatic manipulator as the end-effector, so it can achieve high speed of transplanting. According to transplanting seedlings from high-density plug to the low-density plug, a type of transplanting path was put forward which consists of rise, translation and decline, in this paper, it was called three-stage trajectory. Analysis the movement characteristic of each stage, make sure the stability of transplanting, then the sine motion law, quintic polynomial motion law and septic polynomial motion law were put forward as the Transplanting movement function according the analysis of movement characteristic. Compared the transplanting efficiency and stability of the three motion law through their velocity, acceleration and saltus, finally, quintic polynomial motion law was preferred as transplanting robot motion law. Transplanting experiment was taken on the developed prototype, the transplanting frequency was more than 60 per minute and the qualified rate can reach 92.71%.

이앙직전 벼 육묘상자 살포용 완효성 비료의 처리 효과

벼 재배시 본답의 기비와 분얼비를 대체하여 묘판에 1회 시비하는 용출제어형 입상배합(Bulk Blending) 피복비료를 시용 후 벼 생육과 수량, 품질, 경제성 등 완효성비료의 처리효과를 검토한 결과는 다음과 같다. 1. 개발된 육묘상비료의 T-N용출량은 온도가 높을수록 빨라졌고 온도에 관계 없이 분얼비 시용 시점인 14일경부터 높아져 21일경 최고에 달했다. 2. 이앙 후 60일에서 질소흡수이용율은 표준시비 28.6%에 비하여 개발된 육묘상 비료가 높았으며 200 g시비구에서 73.1%, 300 g시비구에서 66.1%로 나타났다. 3. 생육단계별(최고분얼기, 유슈형성기 등) 초장, 경수, SPAD값 생육상황은 개발된 육묘상비료 300 g/상자 시비에서 표준과 대등하였다. 4. 성숙기에도 간장, 수장, 단위면적당 수수는 개발된 육묘상비료 300 g/상자 이상 시비구에서 표준과 같거나 많았다. 5. 10a당 백미수량은 개발된 육묘상비료 시용량이 많을수록 증가하였다. 시비량별로 보면 표준시비 528 kg 대비 개발된 육묘상 비료 300 g/상자 이상 시비구에서 525~552 kg으로 대등하거나 많았다. 6. 백미 품질은 개발된 육묘상비료 시용량이 많을 수록 단백질함량은 증가하였으며 완전미율, 아밀로스함량, 백도, 투명도는 비료량이 적을수록 증가하는 경향이었다. 7. 따라서 표준시비량 이상의 수량과 품질 및 경제적인 측면을 고려한 개발된 육묘상 비료의 적정 시비량은 300 g/상자(실비. 9 kg/10 a)이었다. 8. 시비량은 육묘상비료가 표준시비에 비해 49.3% 절감되었고, 시비노동력도 49.2% 절감되었다. The newly developed fertilizer is the slow-releasing fertilizer which can be used as a basal fertilizer without no additional fertilization at tillering stage. It has 30-4-6% of <TEX>$N-P_2O_5-K_2O$</TEX> and was coated with mixture of LDPE (Low density polyethylene), EVA (Ethylene vinyl acetate), BDP (Bio degraded polymer), TALC and nonionic surfactant for the controlled release up to 50 days after application. Coating materials were designed to be decomposed naturally. This fertilizer can be applied directly to the seedling tray mechanically just before transplanting, resulting in significant labor saving effect. The developed slow-release fertilizer, which can replace both basal fertilization and top dressing at tillering stage by single application directly to seedling tray, showed the highest release at 14~21 days after transplanting. Considering the plant growth at different growth stages and yield, the optimal application rate of developed slow-release fertilizer was 300 g per rice nursery tray and the yield of rice at this application rate was 5.25 MT/ha. Rice quality in terms of head rice grain ratio, amylose content, whiteness, and taste value decreased as fertilization rate increased from 200 g to 500 g per nursery tray. Fertilization rate based on quantity of fertilizer ingredients (N, P, K) was reduced by 49.3% compared to the standard application rate and there was 49.2% reduction in labor input for fertilization.

The Research and Application of Seeding Machine's Dislocation Type Seeding Device

Because of the rate of rotary seeding sowing machine is low,Turn the cylindrical roller into plane structure, The dislocation type seeding device is designed, The problem about the position relative to the Seedling tray and seeding machine is solved by useiing optoelectronic technology，Experimental results show that the new seeding device’s Seeding accuracy could reach 98%, the working efficiency of the machine is greatly improved.

Improving survival of inter-generic grafts of nematode-susceptible watermelon cultivars and nematode-resistant Cucumis species

Inter-generic grafting of highly nematode susceptible watermelon (Citrullus lanatus) cultivars onto nematode-resistant wild watermelon (Cucumis africanus) and wild cucumber (Cucumis myricoarpus) had on average 36% graft survival ratios, which was attributed to unequal stem diameters at the graft union. Cucumis species had smaller stem diameters at the graft union, whereas Citrullus had bigger ones. The objective of the study was to improve inter-generic graft compatibility of Citrullus and Cucumis through optimizing the sizes of stem diameters during grafting. Cucumis species were raised in a 160-hole seedling tray and primed seeds of Citrullus were raised in a 200-hole seedling tray seven days after emergence of Cucumis in order to reduce the stem diameters. At grafting, stem diameter ratios in various treatments were equal to one, whereas at 66 days after grafting the ratios were grater than one, with the exception of those of intact plants. Survival of grafts from grafting to 66 days after grafting was 100%, translating into relative improvement of 186%. Improved survival of grafts would invariably promote the potential uses of inter-generic grafting among wild and cultivated watermelon in management of soil-borne pathogens.

Acidovorax citrulli Seed Inoculum Load Affects Seedling Transmission and Spread of Bacterial Fruit Blotch of Watermelon Under Greenhouse Conditions.

Infested seed are typically the primary source of inoculum for bacterial fruit blotch (BFB) of cucurbits. An inoculum threshold of 1 infested seed per 10,000 seeds is widely used in seed health testing for Acidovorax citrulli. However, the influence of seed inoculum load on BFB seedling transmission has not been elucidated. In this study, watermelon seedlots (128 seeds/lot) containing one seed inoculated with A. citrulli at levels ranging from 1 × 101 to 1 × 107 CFU were used to investigate the effect of seed inoculum load on seedling transmission and spatiotemporal spread of BFB under greenhouse conditions. The relationship between A. citrulli seed inoculum load and frequency of BFB seedling transmission followed a sigmoidal pattern (R2 = 0.986, P = 0.0047). In all, 100 and 96.6% of seedlots containing one seed with 1 × 107 and 1 × 105 CFU of A. citrulli, respectively, transmitted the pathogen to seedlings; in contrast, the proportion of seedlots that yielded BFB-infected seedlings was lower for lots with one seed infested with 1 × 103 (46.6%) and 1 × 101 (16.7%) CFU of A. citrulli. The relationship between A. citrulli seed inoculum load and frequency of pathogen detection in seedlots using immunomagnetic separation combined with a real-time polymerase chain reaction assay also followed a sigmoidal pattern (R2 = 0.997, P = 0.0034). Whereas 100% of samples from seedlots (10,000 seeds/lot) with one seed containing ≥1 × 105 CFU tested positive for A. citrulli, 75% of samples from lots with one seed containing 1 × 103 CFU tested positive for the pathogen, and only 16.7% of samples with one seed containing 10 CFU tested positive. Because disease transmission was observed for lots with just one seed containing 10 A. citrulli CFU, zero tolerance for seedborne A. citrulli is recommended for effective BFB management. The seedling transmission experiments also revealed that temporal spread of BFB in 128-cell seedling trays increased linearly with A. citrulli inoculum load (r2 = 0.976, P = 0.0037). Additionally, the frequency of spatial spread of BFB from an inoculated seedling in the center of a planting tray to adjacent healthy seedlings over one-, two-, or three-cell distances was greater for lots with one seed infested with at least 1 × 105 CFU than for lots with one seed infested at lower inoculum loads (1 × 101 and 1 × 103 CFU/seed).

Determining Salinity Threshold Level for Castor Bean Emergence and Stand Establishment

ABSTRACTCastor bean (Ricinus communis L.) is grown on marginal lands that can be prone to having medium to high salt concentrations. This study was done to identify a salinity threshold level for castor bean emergence and stand establishment. Seedlings were first cultured in organic matter–soil mixed media at different salinity levels (0.5, 3.6, 7.1, 10.4, and 13.6 dS m−1) and then transplanted into pots filled with soils at similar salinity levels (0.4, 3.6, 7.1, 10.4, and 13.6 dS m−1). Emergence, survival, seedling growth, nutrient accumulation, and leaf photosynthetic parameters were determined. The salinity threshold level was identified at 7.1 dS m−1 At this salinity level or lower, the emergence rate and survival rate reached 75% or higher; and seedling growth, nutrient accumulation, and leaf photosynthetic parameters were not severely affected. As the salinity level increased to 10.4 and 13.6 dS m−1, emergence rate dropped to below 70%, and survival rate below 50%. Photosynthetic rate and stomatal conductance were reduced by up to 66% and chlorophyll reading by up to 24%. Nutrient uptake and accumulation were also significantly reduced at these two salinity levels. Our results indicate that castor bean could be cultured in plastic seedling trays filled with organic matter–soil mixed seedling media and then transplanted into conventional soils provided that the salinity levels in seedling media and conventional soils are ≤7.1 dS m−1

Posições das mudas de alface nas bandejas de poliestireno e efeitos na normalidade e homogeneidade dos erros na produção de plantas

A qualidade de um experimento pode ser descrita por intermédio de estatísticas, sendo o erro experimental um dos parâmetros de avaliação dessa qualidade. O objetivo do trabalho foi verificar a interferência de diferentes posições de mudas de alface em bandeja de poliestireno sobre a normalidade e homogeneidade dos erros em experimentos realizados em estufa plástica e em campo. Foram conduzidos seis experimentos no Departamento de Fitotecnia da Universidade Federal de Santa Maria, sendo três no verão (2006-2007) e três no outono-inverno (2007) com a cultura da alface, cultivar Vera. Os tratamentos foram 12 diferentes posições das mudas na bandeja de produção. As variáveis analisadas na produção de mudas e após o transplante aos ambientes foram a fitomassa fresca e seca da parte aérea e raiz e fitomassa fresca e seca da parte aérea, respectivamente. Foram testadas as normalidade e homogeneidade dos erros sendo comparadas às médias de cada tratamento. Há atendimento da homogeneidade e normalidade dos erros para as fitomassas fresca da parte aérea e de raiz de alface nos experimentos com diferentes posições de mudas na bandeja de produção, nos diferentes ambientes e estações sazonais de cultivo. Para a fitomassa seca da parte aérea não há atendimento da homogeneidade e/ou normalidade dos erros nos experimentos no verão, com produção de mudas e de plantas na estufa plástica. Para a fitomassa seca de raiz não há atendimento da normalidade dos erros no experimento no outono-inverno com produção de mudas.

Diversity and Antimicrobial and Plant-Growth-Promoting Activities of Endophytic Fungi in Dendrobium loddigesii Rolfe

Endophytic fungi are ubiquitously distributed in orchids and have a great impact on the host plant. The diversity of endophytic fungi in the medicinal orchid Dendrobium loddigesii Rolfe was investigated and their bioactivities in microbe and plant growth were explored here. Endophytic fungi were identified by using morphological and molecular biological methods. Antimicrobial activity was determined by a standard disk assay. Activity in promoting plant growth was confirmed by root inoculation of endophytic fungi in seedling tray and pot experiments. Overall, 48 isolates were isolated from D. loddigesii and identified to belong to 18 genera, with Fusarium and Acremonium being the most dominant populations. A total of 17 isolates belonging to 9 genera were screened for their antimicrobial activity, and Fusarium spp., 8 of the 17 isolates, was also the dominant population. In the seedling tray experiment, two isolates, one of Fusarium named DL26 and the other of Pyrenochaeta named DL351, were shown to enhance plant growth in alder bark–humus medium, and the latter displayed weak activity against Bacillus subtilis (As 1.308) and Aspergillus fumigatus (As 3.2910). In the pot experiment, after inoculation of DL26 and DL351, five out of seven media were fit for plant-endophyte symbionts. Medium #1 of red brick fragments and sphagna was optimal in accelerating plant growth. In conclusion, a great diversity of endophytic fungi in D. loddigesii was first confirmed in a considerable proportion of antimicrobial isolates. Furthermore, two endophytes exhibited the ability to enhance plant growth although their activities were influenced by the growth media.

Transplanting young seedlings in irrigated rice fields: Early and high tiller production enhanced grain yield

Transplanting rice seedlings 20 days old or older has been commonly reported to generate an increase in grain yield as a result of higher tiller production. A series of experiments was conducted at the IRRI farm during the dry and wet seasons to quantify, in a range of plant types, the impact of even younger seedlings and contrasting nursery management on grain yield and to identify plant traits supporting high performance under a given establishment technique. Seedling age at transplanting, ranging from 7 to 21 days, and contrasting nursery types (seedling tray, dapog, mat nursery, and traditional wet-bed seeding) were evaluated for an elite line, a new plant type and hybrid rice. To avoid any confounding effect, sowing date in the nursery, seed rate and crop management in the main field were all the same. In the two seasons, and for all genotypes and nursery types, transplanting older seedlings induced a delay in the onset of linear dry matter accumulation and tiller emergence, while the rate of dry matter accumulation and tiller emergence was unchanged. This delay reduced nitrogen content in the seedlings. Plants recovered quickly, however, after transplanting. The delay also reduced maximum tiller number, and extended crop duration with delayed maximum tillering, flowering and maturity. Grain yield was consistently higher for younger seedlings, with, in some cases, a difference as large as 1 t ha −1 between 7- and 21-day transplanting. This result was valid for the four genotypes evaluated, with a higher impact during the dry season. In contrast, no significant difference was observed for the influence of nursery type on the timing of tiller emergence and on grain yield. Some differences in seedling vigor (plant dry weight, specific leaf area, N content), higher in the case of dapog and wet bed, and in maximum tillering, higher in the case of the seedling tray, however, were observed. But these differences did not have a significant impact on the late increase in crop dry matter and on panicle number at maturity. No significant interaction between seedling age and nursery management for all genotypes and for all the parameters measured was found. Promoting early tiller emergence as a response to transplanting young seedlings increased grain yield in all cases despite the associated decrease in tillering efficiency. Extended growth inside the nursery, rather than transplanting shock per se, appeared to be the main reason for delayed tiller emergence in late transplanting.

(424) Vigor Testson Lettuce Seeds and Their Correlation with Emergence

The main objective of this study was to evaluate some of the available seed vigor tests to predict lettuce (Lactuca sativa L.) seedling emergence. Eight lettuce seed lots were evaluated by the following laboratory vigor tests: germination (GT); accelerated aging (AA); saturated salt accelerated aging (SSAA); conductivity (EC); and seed vigor imaging system (SVIS). Also evaluated were the percentage (EP) and speed (ES) of the seed lots' emergence under three conditions: seedling trays (ST) filled with a mixture of peat (80%) and perlite (20%); boxes with a clay loam soil (BS); and boxes with a mixture of clay loam soil (66%) and sand [34% (BSS)]. Correlation coefficients among the laboratory and emergence test results were calculated and significant differences were found. The correlation coefficients between EC results and each emergence parameter were nonsignificant, while AA results were only significantly correlated with the emergence percentage for BSS. GT values and emergence results were significantly correlated in all cases. SSAA results were equally or more positively correlated than GT results with the EP and, for the three sowing conditions, they were more correlated with the ES than GT values. Vigor index results from the SVIS were significantly correlated with both emergence parameters, and its correlation with emergence on ST (EP and ES) was greater than GT values. The results of this study showed that SSAA and SVIS were the best laboratory tests for lettuce seed vigor evaluation, especially for seed lots to be used for plug seedling production.