| Aims: Rice cultivation by drip irrigation with plastic film mulch(DIPM)is a new water-saving rice cultivation method first proposed by Xinjiang Tianye Ltd.. DIPM showed great water-saving and yield potential in practice. While DIPM rice suffer from chlorosis at seedling stages in calcareous soil, especially when soil temperature is low. The symptom of chlorosis is new-born leaf become yellow with stuned growth, if low temperature last for a long time, plant will die. Chlorosis syptom can recovery if temperature rise. Chlorosis restrict DIPM from extension in practice. This thesis aims to study on the mechanism of rice iron deficiency chlorsis and prevent it from occurring by four methods: Fe fertilizer application to rice sddelings, soil acidification, delayed sowing data and plant growth regulation agent application..Methods: The research conducted at Xinjiang Tianye Agricultural Research Institute in 2013 to 2014. Lowland rice genotype T-43(Oryza sativa L.) was used in this study. Iron fertilizer application experiment aimed to study the effects of two iron source and two application methods on chlorosis repairment. The experiment(in the year 2013) had 5 treatments: controls(CK), drip irrigated Fe SO4(DF), Fe SO4(PF) by foliar spraying, drip irrigated EDTA-Fe(DE), and EDTA-Fe(PE) by foliar spraying. The dosage of all of the 4 treatments was 0.9kg/hm2. Leaf chlorisis index, SPAD value, root vigor, biomass and yield were measured to test the effect of exterial Fe application on rice chlorosis. Soil acidification and delayed sowing data experiment is a two-factor split-plot experiment. Soil temperature is the main factor. Rice was sowed when soil temperature at 12℃(T1), 15℃(T2),and 18℃(T3). The secondary factor was soil acidifiers: ASmonium sulfate with nitrification inhibitor(AS), phosphoric acid(PP), citric acid(CA), and contrast(CK). The acidifier splittly applied by three times at 5, 11, 17 days after seeding. P dosage is 25% total P2O5 dose. The dosage of ASmonium sulfate is equal to mol number of PP. Citric acid ASount equal to 8% of N fertilizer dosage. Soil p H, soil available iron, leaf available iron, leaf chlorisis index, SPAD, root vigor, biomass were measured to study the effects soil temperature and soil acidification on rice iron chlorisis. Three growth regulators, naphthylacetic acid(NAA), compound sodium nitrophenolate(CSN), diethyl ASinoethyl hexanoate(DA-6) was adopted to test how they effects on rice chlorosis, application methods was seed soaking and soil application. The concentration was NAA 0.01 ppm, CSN 5ppm, DA-6 0.5ppm in seed soaking, in soil application the concentration of growth regulator was 10 times based on soaking treatment. Leaf available iron content, leaf chlorisis index, SPAD value, root vigor were measured to study the effects that plant growth regulator on rice chlorisis.Results: 1) EDTA-Fe fertigation and foliar spraying significantly reduced leaf chlorisis index, while application of Fe SO4 did not release rice young leaf chlorosis index. Iron fertilizer application did not significantly increased leaf SPAD value compared with CK. 2) Application of EDTA-Fe significant increases dry matter in seeding stage, but no significant effect on root vigor, the s ASe as application Fe SO4. Iron fertilization application has no significant effect on yield and yield components. 3) AS, PP, CA treatments decreased the soil p H by 0.31, 0.10, 0.04 units respectively after three split application, and increased soil DTPA-extractable iron by 75.2%, 45.3%, 34.9% compared with CK, respectively. Soil p H and available iron content in PP treatment showed sharp change in a single application cycle, while in CA treatment, soil p H and available Fe content changed weakly. Soil p H were gradual decline and soil available iron gradual increased for AS treatment, that showed acidfying effect of AS tend to accumulative and last for a longer time, the acidification effect of PP is strong but last for a short time, and the acidification of CA is weak. 4) Delayed sowing data treatment reduced rice leaf chlorisis index and increased rice leaf available iron and SPAD value significantly, it showed that have a similar result in soil acidulant treatments. AS treatment significantly reduced rice young leaf chlorosis index in seeding stage. Three acidification treatments significant increased rice leaf active iron content, the content of them was in the order AS>PP>CA and increased iron content by 14.4%、11.3% and 9.2% compared with CK. The three acidification treatments significant increased rice shoot dry matter in seeding stage. the weight of them was in the order of AS>PP>CA and increased weight by 14.4%,11.3%,9.2% compared with CK. Delay sowing data is benefit for dry matter accumulation. 5) Rice root vigor showed significant differece between the three acidulant treatments and AS treatment showed the hightest root vigor. Three acidulant treatments significant increased on the rice root volume. There were no interactions between sowing date and acidulant treatments. The results showed that rice root length, root suface area and root volume increased with a rise in soil temperature. 6) CSN application in soil increased rice root vigor, root length, root sufarea and root volume significantly and increased rice leaf active iron content SPAD value.Conclusions: 1)Two reasons result in rice chlorosis under DIPM in seedling stage:(1) Low available iron content of calcareous soil, especially when air temperature is low.(2). Low soil temperature limited root development and reduced root vigor, hence uptake of nutrient iron from soil was restricted. 2) Iron fertilizer application was not an ideal method for guarding against iron deficiency chlorosis. 3) Application of acidifier helps overcome rice chlorisis under DIPM, nitrification inhibitor plus ASmonium sulfate was the best approach. 4) Appropriatly delay sowing date was helpful for preventing seedling chlorosis but it was not admirable in area where the available accumulative temperature is low. 5) CSN application in soil was an effective method to prievent rice seedling chlorosis... |
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