Studies On Nutrient Physiology And Optimum Fertilization Management Of Tomato Long Term Cultivation In Eco-organic Soilless System

Tomato is one of the staple vegetables in protected cultivation in China, The main factors whichaffect the yield of greenhouse tomato production are greenhouse environment, crop fertilization andirrigation management. Although in recent years much attention has been paid in growing media,fertilization and irrigation for short term tomato cultivation in Eco-organic type soilless culture (EOTSC)system in which crop is directly fed with solid fertilizer instead of nutrient solution, information onnutrient physiology of long term tomato cultivation in EOTSC system in greenhouse is scantyThe present study was undertaken to examine dynamic change of EC and pH value in growingmedia, mechanism of root activity adjustment, absorption pattern of nutrient elements, optimumfertilization rate and its verification in field with tomato crop for long term cultivation in EOTSC systemin greenhouse. The main results are as follows:1. In EOTSC system which uses solid fertilizers rather than nutrient solution to feed plantsand just irrigates fresh water during the whole period of crop growth, top dressing fertilizerincreased the buffer capacity of pH and EC change in growing media. The range of pH and ECchange in substrates could be within the acceptable levels for meeting crop growth requirement as longas additional solid fertilizer was applied at suitable interval. Over irrigation would build up pH value(in hard water region) and decrease EC value in substrates. Further research activities would beexpected to carded out for adjustment techniques of optimum pH and EC level in growing media.2. In winter low temperature season, tomato root activity and leaf net photosynthesis rate could beenhanced by application of plant growth regulators, such as 2,4-D; yunda-120; uniconazole (UNI);salicylic acid (SA); NAA and compound sodium nitrophenolate (CSN) in substrates. Tomato planttreated with yunda-120, CSN+NAA increased root activities by 0.623mg TTC/h.g and 0.558 mgTTC/h-g respectively which were very significant higher than that of control, enhanced leaf netphotosynthesis rate and plant stem growth, consequently increased tomato yield by 13.42% and 8.78%respectively as compared with control.3. With the amount of top dressing fertilizer (TDF) increasing, the content of N, P₂O₅ and K₂O inroot, stem and leaf of tomato plant increased. But whatever TDF amount was high or low, the content ofN, P₂O₅ and K₂O in root, stem and leaf of tomato plant decreased gradually in winter low temperatureseason as compared with those in fall or spring season, it was due to low temperature in substrates whichdecreased tomato root activity and further resulted in root absorption ability of N, P₂O₅ and K₂Odeclining,.4. On the condition of moderate fertilization, the percentage of N, P₂O₅ and K₂O distribution infruit was obviously higher than those of high fertilization and low fertilization treatment. It indicated thatmoderate fertilization increased the transportation of N, P₂O₅ and K₂O to fruit, and enhanced fruitgrowth and fruit yield. While high fertilization increased the transportation of N, P₂O₅ and K₂O to leavesand resulted in higher percentage of N, P₂O₅ and K₂O distribution in leaves.5. In moderate fertilization treatment, the content of N and K₂O in growing media maintained stable, and P₂O₅ content in growing media had a increasing trend; there was declining tendency in lowfertilization treatment and increasing tendency in high fertilization treatment in terms of the content of N,P₂O₅ and K₂O in growing media. It indicated that moderate fertilization could keep ability of supplyingnutrient elements to meet plant growth need and avoid the accumulation of nutrient elements in growingmedia, while high fertilization would build up salinity in growing media.6. By establishing related equation models between nutrient N, P, K fertilization rate (mixture oforganic and inorganic fertilizers) and yield of long term tomato cultivation at different growth stage inEOTSC system, the optimum fertilization rates at different growth stage of long term tomato productionwere recommended. The N, P₂O₅ and K₂O nutrient had significant effect on tomato early, middle andlate yield. The optimum fertilization rate of N, P₂O₅ and K₂O were 0.72 (g/plant/time, the same as thefollowing), 0.32 and 1.04 respectively during early growing stage of tomato; The demand for N and Kincreased during middle growth period, the optimum fertilization rate of N, P₂O₅ and K₂O were 0.85,0.22 and 1.40 respectively; And then demand for N and K slightly decreased during late growth period,the optimum fertilization rate of N, P₂O₅ and K₂O were 0.78, 0.25 and 1.27 respectively.In the verification trial on the basis of recommended fertilization rates, the early, middle, late andtotal yield of tomato fruits per plot by supplying recommended fertilization rates reached 15.8kg, 26.8kg,18.5kg and 60.5kg respectively; the yield was in line with the yield derived from the equation models.The yields in the treatment of supplying recommended fertilization rate were the highest, either early,middle, late yield or total yield, in all the treatments, and had significant differences as compared withthe control (conventional fertilization). It indicated that the recommended fertilization rates derived fromthe equation models could be applied in long term tomato cultivation.