Alleviation of drought stress in rice through nutrient and crop management strategies | |
| Author | Das, Debesh |
| Call Number | AIT Diss no.AS-22-01 |
| Subject(s) | Plants--Effect of stress on Plants--Drought tolerance Water in agriculture Rice |
| Note | A Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Agricultural Systems and Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Climate change and agricultural malpractices are exacerbating drought in many parts of the world causing a substantial agricultural production loss. Rice (Oryza sativa L.) is a semi-hydrophyte and highly sensitive to water-deficit stress. Maintaining a high water productivity along with an improved tolerance against drought are crucial for sustainable rice production under reducing fresh water availability. Traditional rice production systems and existing technologies are not sufficient to meet the ever increasing global food demand. Innovative agronomic management practices (nutrient management and crop establishment method) and efficient irrigation strategies should be incorporated with existing cultivation practices for sustainable rice production to maximize yield and water productivity. An adoption of water-saving irrigation, such as alternate wetting and drying (AWD), coupled with a balanced nutrient management is required for improving drought tolerance in rice and enhancing grain yield and water productivity. Therefore, an interactive effect among nutrient management practice, mycorrhizal fungi inoculation, and crop establishment method under AWD irrigation was evaluated through a series of polyhouse experiments for lowland rice.In the first polyhouse experiment, factorial combination of seven priming treatments (non-primed control, hydropriming, Trichoderma, silicon dioxide, salicylic acid, potassium nitrate, and abscisic acid) and three soil water potential levels maintained through AWD irrigation (0, –15, and –30 kPa) was evaluated to explore potential benefits of seed priming in mitigating water-deficit stress. Grain yield was not significantly different between 0 and –15 kPa regardless of priming treatments. However, it was reduced at –30 kPa under all treatments, except for Trichoderma. Seed priming with Trichoderma resulted in 52%, 68%, and 77% higher grain yield and 52%, 70%, and 66% higher water productivity at 0, –15, and –30 kPa, respectively, than the control. Rice can be safely grown with AWD irrigation level up to –15 kPa. However, seed priming with Trichoderma is recommended where frequent irrigation is difficult to practice and soil water potential drops below –15 kPa. Seed priming with potassium nitrate is also a promising option when soil water potential drops below –15 kPa.The second factorial experiment consisting of four monosilicic acid (MSA) doses (0, 75, 150, and 300 kg ha–1 ), two levels of arbuscular mycorrhizal fungi (AMF) inoculation (inoculation of AMF [+AMF] and without inoculation of AMF [–AMF]), and three soil moisture regimes (100%, 75%, and 50% field capacity [FC]) was conducted to evaluate the effect of silicon (Si) and AMF inoculation on growth, yield, and water productivity of rice under water-deficit stress. The soil moisture regimes of 75% and 50% FC indicate a 25% and 50% depletion of the maximum amount of water held in the soil, respectively, whereas 100% FC refers to the maximum amount of water held in the soil after gravitational water drainage stops. An overall reduction in growth and yield of rice was observed with decreasing soil moisture regime; however, an application of 300 kg MSA ha–1 increased shoot dry matter by 28% compared with 0 kg MSA ha–1 under limited soil moisture availability of 75% and 50% FC. Similarly, grain yield was increased by 37% and 39% at 300 kg MSA ha–1 compared with the control in the –AMF and +AMF plants, respectively, under moderate soil moisture level of 75% FC. The corresponding increase at 50% FC was 52% and 55%, respectively. The results demonstrated a synergistic effect of exogenous application of MSA at 300 kg ha–1 (60 kg ha–1 soluble Si) and AMF inoculation on rice under water-deficit stress.The third polyhouse experiment consisting of three factors, namely six fertilizer doses including different combinations of potassium (K) and Si along with nitrogen (N) and phosphorus (P) and the control (NP100 [control], NP100 + K100, NP100 + Si100, NP100 + K75 + Si25, NP100 + K50 + Si50, and NP100 + K25 + Si75), three soil water potential levels (0, –15, and –30 kPa), and two cultivation methods (wet direct seeding and transplanting), was conducted to assess the response of rice in terms of growth, physiological traits, yield, and water productivity. Supplementing N and P with only K (NP100 + K100) assisted in alleviating the harmful effect of water-deficit stress, and resulted in 11%, 8%, 47%, 40%, 40%, and 42% higher leaf greenness, leaf relative water content, net photosynthetic rate, free proline content (wet direct-seeded plants), grain yield (wet direct-seeded plants), and water productivity, respectively, than NP100 at – 30 kPa, while transpiration rate was reduced by 22% for the same treatment combinations. Silicon supplementation either with NP100 alone or in combination with different proportions of K also promoted rice growth, physiological traits, and grain yield; however, the response of rice was largely similar among different K and Si combinations, except for NP100 + K25 + Si75. Inclusion of K and Si with N and P in a fertilizer management program where the share of K is at least 50% could be a promising approach to minimize the harmful impact of water-deficit stress in rice cultivated through either wet direct seeding or transplanting method. The fourth polyhouse experiment consisted of four fertilizer treatments where the P percentage varied along with the recommended dose of N with or without AMF inoculation (P100 as the control, P100 + AMF, P75 + AMF, and P50 + AMF), three soil water potential levels [0, –15, and –30 kPa], and two cultivation methods (wet direct seeding and transplanting). Data were collected on selective growth parameters, physiological traits, mycorrhizal inoculation, yield components, grain yield, and irrigation water productivity of rice. The results revealed that P100 + AMF inoculated plants had 14%, 11%, 74%, and 54% higher leaf relative water content, leaf greenness, net photosynthetic rate, and grain yield for wet direct-seeded plants at reduced soil water potential (–30 kPa) compared with non-inoculated plants (P100). Proline accumulation gradually enhanced with reducing soil water potential, which was maximized at –30 kPa by 77% for P50 + AMF (for transplanted plants) that slackened leaf osmotic potential and in turn helped in better osmotic adjustment than non inoculated plants. AMF inoculation improved physiological response for most of the evaluated traits of rice and enhanced grain yield with P availability (even with a 25% reduction in its recommended dose) in the rhizosphere under drought stress. It can be concluded that AMF inoculation coupled with judicious P management is a promising approach for improving physiological and biochemical traits, grain yield, and irrigation water productivity of rice under AWD irrigation. |
| Year | 2022 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural Systems and Engineering (ASE) |
| Chairperson(s) | Datta, Avishek; |
| Examination Committee(s) | Salin, Krishna R.;Tsusaka, Takuji W.; |
| Scholarship Donor(s) | Bangabandhu Science and Technology Fellowship Trust, Ministry of Science and Technology, Bangladesh; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2022 |