| Density and nitrogen, which are the important controllable factors of tomato cultivation,have great effects on enhancing yield, improving fruit quality, regulating plant type and optimizing the canopy structure. Excessive pursuit for high nitrogen, high density and high multiple culture in greenhouse has caused some problems such as succession cropping obstacle, serious diseases and pests and decrease of yield. The research adopted the way of selecting the proper density and nitrogen amount at first, and then testing the result of first study and for the further exploration. Effects of density and nitrogen on tomato cultivated in greenhouse substrate bags were investigated, aiming to build high yield methods of enhancing density and decreasing nitrogen for tomato, to improve land use efficiency, to reduce dependence on nitrogen fertilizer and to provide the technical basis for efficient production of facilities cultivated tomato.With tomato cultivar “hui-yu” as material, it adopted bag cultivation and two factors of density and nitrogen amount of single plant, which including five density levels(the regular density D1: 4 plants/m2, D2: 6 plants/m2, D3: 8 plants/m2, D4: 11 plants/m2 and D5:17plants/m2, respectively) and four nitrogen fertilization amounts of per plant(N1, N2, N3, N4:12174mg/plant, 11581mg/plant, 10989mg/plant and 10396mg/plant, respectively), and the effects of different combinations of cultivation density and nitrogen fertilization amount of per plant were investigated on growth, photosynthetic characteristics, canopy structure,enzyme activity of nitrogen metabolism and yield. The results are as follows:1.Density and nitrogen fertilizer amount had significant effect on growth of tomato plant.When the density was at certain level, the plant height, stem diameter, leaf area and SPAD value all decreased with decline of nitrogen fertilization, however, the decrease was transferred into no significant at mature stage. Meanwhile, when the nitrogen fertilization amount was at a certain level, the increasing of density decreased all parameters talked above.The plant height, stem diameter, leaf area and SPAD value of D3N2 decreased by 13.15%,12.55%, 32.95%, 8.2% averagely compared with that of D1N1 at different growth stages,respectively.2.Density and nitrogen fertilization amount had different effects between dry matter ofsingle plant and that of unit area. When density was at certain extent, the change regulation was the same, that was, when the density was D1 and D2, the dry matter of both types all decreased with decline of nitrogen fertilization amount, and when it was under the D3 level,the dry matter of both types all showed a tendency as fallows: N2>N3>N1>N4. When the nitrogen fertilization amount was at certain level, it showed different changes. With increase of density, at fruit sitting stage and fruit expanding stage, dry matter of single plant dropped down, however, at mature stage, it declined when the nitrogen was at N1 and N4 levels and increased at N2 and N3 levels; it showed a gradually increasing tendency for dry matter of unit area.3.The change trends of leaf net photosynthesis rate(Pn) and stomatal conductance were similar under different treatments of density and nitrogen fertilization, however, that of leaf net photosynthesis rate and intercellular CO2 were opposite. When the density was at certain level, Pn decreased with decline of nitrogen amount under D1 and D2 condition. The Pn of D3N2 was the highest and had no significant difference with DIN1. When nitrogen fertilization amount was at certain extent, Pn decreased with increase of density at N1, N3 and N4 levels. The Pn of D3N2 was the highest while that of D2N2 was the opposite. It showed no significant changes regulation for transpiration rate under different treatments, and the highest transpiration rate was obtained at fruit expanding stage.4.Density and nitrogen fertilizer had notably effects on activity of leaf nitrogen metabolic enzymes. When the density was at D3 level, N2 had the highest activity of NR and GS, and which had no significant difference with that of D1N1.5.Density and nitrogen fertilization had dramatically difference on canopy structure.When density was at certain level, decline of nitrogen decreased leaf area index(LAI). When the nitrogen amount was at certain extent, LAI increased with increase of density. The LAI of D3N1 and D3N2 were getting the optimum about 15 day(about 3~4 for LAI) after the first measurement and were notably higher than that of other treatments. With development of tomato plants, the leaf area index of D3N1 was still increase, and keep a level of above 4. The LAI of D3N2 the optimum LAI for about 40 days and then all decreased rapidly at latter growth stage. D1N4 had no optimum LAI at all growth stages.When the density was at a certain level, light transmission increased within the distance of 120 cm between the ground and lower-layer leaf with decrease of nitrogen, however, the extinction coefficient of different canopy of leaf position increased. When the nitrogen amount was at certain extent, light transmission decreased and extinction coefficient increased with the increase of density within all canopy leaf position. Especially, below 40 cm leaf-layer,lighting conditions were poor.The biggest difference of transmittance among various canopyleaf position of D3N2 with the uniform illumination was 32.6%; however, the extinction coefficient of D3N2, D3N3 and D2N3 decreased with increase of height of canopy structure leaf, and the different values were 0.453, 0.409, 0.318.6.Density and nitrogen fertilization amount had remarkable effects on fruit quality. When density was at a certain level, nitrates, soluble protein, soluble sugar and Vc content of tomato fruit decreased with decreasing of nitrogen fertilizer. Meanwhile, when nitrogen fertilization was at certain extent, nitrates, soluble protein and Vc of tomato fruit increased with increasing of density, however, the nitrate content was reduced. Subordinate function values analysis showed the total value of the subordinate function of D3N1 and D3N2 were 5.093 and 4.782,respectively, and was significantly higher than that of other treatments and had a good comprehensive quality fruit.7.Density and nitrogen fertilization amount had significant effects on yield of tomato.When the density was at certain level, decline of nitrogen decreased the yield under density condition of D1 and D2, however, when the density was at D3 level, the yield showed a tendency of N2>N3>N4>N1. When the nitrogen amount was at certain level, with the increase of density, the yield of all treatments showed a tendency of D3>D2>D1 under N1 condition, while when the nitrogen was N2, N3 and N4 level, yield increased. Under the nitrogen treatment of N2, the yield of D4(11plants/m2) and D5(17plants/m2) decreased significantly, which decreased by 52.45% and 64.97% compared with regular cultivation,respectively.8. To comprehensively considered the development, canopy structure, fruit quality and yield of tomato, the cultivation density of 8 plants/m2 and nitrogen fertilization of 11581mg/plant was the optimal value of enhancing density and decreasing nitrogen fertilization amount for facility tomato cultivated in bag, under which condition can obtain the highest yield of 113.71 t/hm2. |
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