Phytophthora nicotianae transmission and growth of potted kalanchoe in two recirculating subirrigation systems

Recirculating subirrigation systems are frequently exposed to the risk of plant pathogens transmission, which may deteriorate the growth and quality of the plants. The transmission of Phytophthora nicotianae was examined using Kalanchoe blossfeldiana cv. New Alter in two recirculating subirrigation systems, a nutrient-flow wick culture (NFW) system and an ebb and flow (EBB) system. When the nutrient solution was infested, the pathogen was recovered from roots in both subirrigation systems. However, foliar blights and browning of roots appeared 4 and 7 weeks, respectively, after inoculation in the EBB system. Only a little discoloration appeared in the NFW system. The fresh and dry weights were lower in the EBB system than in the NFW system. When growing medium was inoculated, the pathogen was unable to be isolated from the plants in the NFW system. However, disease symptoms appeared in the EBB system 4 weeks after inoculation, and the pathogen was observed in the basal leaves and roots. Similar to the infested nutrient solution, the plant growth in the EBB system was inhibited. These results suggested that when the nutrient solution was infested, pathogen transmission could occur in plants in both systems, although differences existed with regard to disease symptoms and the time it took for symptoms to appear. However, we observed that when growing medium was inoculated the pathogen was not transmitted to adjacent plants in the NFW system using wick.     

The influence of irrigation system and nutrient solution concentration on potted geranium production under various conditions of radiation and temperature

Zonal geranium (Pelargonium × hortorum ‘Real Mintaka’) were grown in closed soilless systems to evaluate the effects of irrigation system (drip and subirrigation) and nutrient solution concentration (half and full) under various conditions of radiation and temperature (winter and summer) in terms of substrate electrical conductivity (EC_s), growth, quality, crop evapotranspiration (ET_c) and growth index water use efficiency (WUE_GI) and nutrient uptake. At he end of the cultural cycle the highest EC_s in the upper and lower layers were recorded in the spring season on plants grown in subirrigation using a full nutrient solution concentration. The highest shoot biomass, leaf area, plant growth index, and quality index were recorded in the winter season on plants grown in both drip-irrigation and subirrigation using half and full nutrient solution concentration, whereas the lowest value was observed in the spring season on plants grown with subirrigation using the full nutrient solution concentration. The highest maximum air temperature recorded during the first 20 days after transplanting in the spring growing season was presumably responsible for the reduction in shoot biomass production, growth and quality index, and in time of geranium flowering compared to the plants grown in the winter season. The ET_c was 44% higher in spring than in winter season treatment, while the effect of the irrigation system was less pronounced with an increase in 11% in the subirrigation treatment compared with the drip-irrigation system. WUE_GI was not stable and showed a seasonal variability. Solar radiaton (R_s), air temperature (T_a) and vapour pressure deficit (VPD) were greatly higher in the spring season, which influenced WUE_GI negatively. The WUE_GI improved especially when R_s, T_a and VPD were below 12 MJ m², 20 °C and 0.6 kPa, respectively. The highest N, and Mg uptake were recorded in the winter season, especially on plants grown with subirrigation at 2 dS m⁻¹. The highest P, K, and Ca uptake values were measured during winter season using subirrigation system, and on plants grown under full strength nutrient solution. The variation of the nitrate concentration and EC in the nutrient solution during the spring growing cycle was less pronounced in the subirrigation than with a drip-irrigation system which represents an important aspect for the simplification of the closed loop management of the nutrient solution.     

杜鹃无土栽培基质配方的研究

 采用发达国家已经大量应用的潮水式(Ebb&Flow)底面灌施营养液栽培系统，以盆栽杜鹃品种‘Mission Bell’作为试材，筛选出适合杜鹃盆花无土栽培 基质配方。混有草炭的M1(体积比：草炭土3+蛭石3+珍珠岩3)、M2(草炭土3+蛭石3+砻糠3)和M4(草炭土2+蛭石2+珍珠岩2+著糠2+腐叶土2)基质配方栽培的植株表现较好，尤以M1处理，即‘草炭土3+蛭石3+珍珠岩3’的等量配方为最优，而椰壳并不适合盆栽杜鹃的植株生长。土壤的理化分析和植物体分析结果表明，营养液灌溉处理后基质的pH值基本相同，但EC值的增幅很大，是由封闭系统内营养液中盐分累积所致；盆内基质中的矿质营养元素和阳离子交换量也明显增加；植物体的营养元素含量水平普遍较高，非常符合杜鹃类植物的生长条件与特殊需求。