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Title of Thesis

Sikader Ali
Institute/University/Department Details
University of the Punjab, Lahore
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
AZOLLA, BIOFERTILIZER, RICE-WHEAT CROPPING SYSTEM, Nitrogen fixation, Azolla pinnata, floodwater, Lepidoptera

Azolla is a free-floating water fern, having a symbiotic nitrogen fixing blue-green alga in its leaves. In rice-Azolla culture this symbiotic association can fix nitrogen comparable to legumes. Greenhouse and field studies were conducted to investigate its use as biofertilizer in rice-wheat cropping system being the dominant cropping system in Pakistan

Before its use in the rice-wheat cropping system, research work was carried out on its natural distribution, selection of heat tolerant strain, cultivation in greenhouse and field conditions, pest control, nitrogen fixation and decomposition, under local conditions

During the survey of rice growing area of the Punjab, Azolla pinnata var. imbricate was found growing in stagnant or slow moving waters during the colder months of the year. Since Azolla is grown during summer and naturally occurring Azolla is sensitive to heat, therefore, through acclimatization processes, a heat tolerant strain was selected for use in greenhouse and field studies

The analysis of floodwater having good growth of Azolla showed that a combination of floodwater properties, like suitable pH, total salt concentration and optimum concentration of essential macro and micronutrients is required for better Azolla growth

The cultivation of Azolla in defined culture media, re-synthesized according to floodwater analysis, showed that its growth was better in one of these culture media when adjusted to pH 8, being the common pH of floodwaters of rice area. The addition of humic acid into culture media increased the Azolla growth and nitrogenase activity as measured by acetylene reduction assay. In addition to defined culture media, simple and economical undefined culture media were also tested. The addition of farmyard manure 10 g/L). Fe (2 ppm) and superphosphate (10 ppm P) to soil-water culture medium was useful for sustaining the Azolla growth for a longer period. Using nutrient missing technique phosphorus was found to be the major limiting nutrient In experimental soils. The application of 10 kg P2O2/ha was sufficient to alleviate this constraint

Amongst the pests, water snails and larvae of Lepidoptera were found to interfere its cultivation. Among the different pesticides tested, Furadan (carbofuran) was found to be the least toxic for Azolla growth and was used for pest control

The effect of combined nitrogen in the culture medium showed that its lower concentration (14 ppm NH4-N) was useful for its growth while the higher concentrations (28 and 42 ppm) decreased its growth and nitrogenase activity. The 15N dilution technique was used to estimate nitrogen fixation under field conditions. It was found that average value for nitrogen derived from air for different strains/species was 78 %, indicating sufficient nitrogenase activity in the presence of nitrogen under the field conditions

The decomposition of Azolla was investigated by using unlabelled and 14C-labelled Azolla by measuring CO2 evolution. It was found that decomposition rate reached to peak value by 10th day after its incorporation and incubation at 30oC. About three-fourth of the Azolla-C was evolved as CO2 within 2-3 weeks. The decomposition rate was faster in moist soil having 30% saturation percentage (SP) of water than at 100% SP

The mineralization of Azolla-N in soil reached to peak by the end of first week of its incubation and remained almost constant thereafter. The rate of mineralization was faster at 30% than at 100% SP and higher amounts of NO3-N was formed at 30% SP whereas higher concentration of NH4-N was observed at 100% SP

The decomposition of Azolla in soil led to formation of humic substances. As estimated by C and N content. about double amount of humic acid and fulvic acid were formed in Azolla incorporated soil than control

The inoculation of Azolla resulted into higher leaf area index and higher rice straw and grain yield of a tall variety i.e. Basmati-370 as compared to control and inoculation of blue-green algae. The use of Azolla alongwith farmyard manure (FYM) produced equal or more grain yield than urea application at 50 kg N/ha in this rice variety

The inoculation of Azolla also increased the yield of a dwarf rice variety i.e. lR-6. Similarly. Azolla cover as well as Azolla grown as intercrop and incorporated during rice growth period resulted in more grain yield. The application of Azolla was found equivalent to 25-45 kg N/ha of urea. The use of Azolla alongwith low amount of urea (30 kg N/ha) was better than urea alone. The use of Azolla alongwith urea increased fenilizer-N use efficiency and also reduced N losses from rice ecosystem. due to lowering of floodwater pH. The use of Azolla as monocrop indicated that its incorporation first time at 10 and second time at 40 days after transplanting (DA T) during rice growth period was better than its incorporation at 40 and 80 DA T during rice growth. A higher increase in rice yield and more 15N from

Azolla was recovered in rice with early incorporation than late incorporation. The Azolla showed a better response for grain yield than urea, whereas chemical-N fertilizer was more useful for increasing straw yield. The application of 15N labelled Azolla and urea indicated that a higher amount of 15N was retained in soil for Azolla than urea as observed after the harvest of rice. To investigate the residual effect of Azolla on the subsequent crop, wheat was grown without any fertilizer application. The residual effect of Azolla alone and alongwith urea was superior to application of urea only. As compared to control, the increase in wheat grain yield was upto 41 % for Azolla treatments. The residual effect was higher when Azolla was incorporated at later stage of rice growth than its incorporation at early stage. Higher amount of 15N was retained in soil after wheat crop for Azolla than urea application, indicating its positive role in increasing the N pool of the soil

The greenhouse and field experiments indicated that Azolla can be cultivated as intercrop alongwith rice using the same time and space. Since Azolla derived 78 % of its nitrogen from air under field conditions. therefore. its use alongwith chemical fertilizer is feasible. The results showed that Azolla can effectively be used as a biofertilizer in rice wheat cropping system under local conditions and a saving of a large amount of chemical N fertilizer and capital is possible

Download Full Thesis
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S. No. Chapter Title of the Chapters Page Size (KB)
1 0
90.42 KB
2 1 Introduction 1
67.8 KB
3 2 Review Of Literature 10
720.2 KB
  2.1 The Azolla Plant 10
  2.2 Ecophysiology 20
  2.3 Use Of Azolla In Rice 27
  2.4 Nitrogen Fixation 42
  2.5 Other Uses 54
  2.6 Constraints, Economics And Potential For Future 56
4 3 Materials And Methods 63
532.36 KB
  3.1 Azolla Survey In Rice Area 63
  3.2 Temperature Studies Of Azolla 67
  3.3 Azolla Cultivation 70
  3.4 Pest Management 78
  3.5 Nitrogen Fixation In Azolla 80
  3.6 Use Of Azolla In Rice 84
  3.7 Residual Effect Of Azolla On Wheat 100
5 4 Results 104
746.13 KB
  4.1 Azolla Survey In Rice Area 104
  4.2 Temperature Studies Of Azolla 109
  4.3 Azolla Cultivation 114
  4.4 Pest Management 124
  4.5 Nitrogen Fixation In Azolla 125
  4.6 Carbon And Nitrogen Mineralization 128
  4.7 Use Of Azolla In Rice 136
  4.8 Residual Effect Of Azolla On Wheat 160
6 5 Discussion 173
496.15 KB
  5.1 Azolla Survey In Rice Area 173
  5.2 Temperature Studies Of Azolla 180
  5.3 Azolla Cultivation 183
  5.4 Pest Management 190
  5.5 Nitrogen Fixation In Azolla 192
  5.6 Carbon And Nitrogen Mineralization 196
  5.7 Use Of Azolla In Rice 201
  5.8 Residual Effect Of Azolla On Wheat 221
  5.9 Possible Fertilizer Saving 213
7 6 References 215
181.65 KB