Projects
Baselining greenhouse gas emissions from Australian rice crops
The project will inform growers on rice growing practices that can help to reduce greenhouse gas emissions from their rice crops and provide the industry with baseline datasets that may be used to develop country-specific rice greenhouse gas emission factors for national greenhouse gas inventory reporting.
Usually, rice is grown by flooding fields with water which blocks oxygen getting to the soil and allows bacteria to grow that breakdown and consume soil organic matter under anaerobic conditions. In doing so the bacteria let off a potent greenhouse gas called methane, most of which is released to the atmosphere from rice fields though the rice plants themselves. The plants have small air spaces in their roots and stems which are connected. Methane moves into the roots from the soil and travels up to the stems a bit like a straw, where it escapes from the plant into the air through tiny micropores on stem and leaf surfaces. Newer, drill sown rice growing practices, which use less water and are quite common in Australia, involve the farmer delaying the time at which the field is completely filled up with water for several weeks after planting. The seed is drilled directly into soil and then established by periodically flushing the field with irrigation water several times for several weeks until a few leaves have grown.
Since flushing is where the field is filled up with water and then drained within 12-24 hours, it allows the soil to remain in contact with the air and retain oxygen which prevents the special methane producing bacteria from being able to survive, no methane is produced and so none is available for release to the atmosphere from the rice field. Only after several weeks after planting and the first flush irrigation is applied, is the field completely filled with water.
The number of days that methane can be produced is reduced by 50 days or sometimes even more, over a 150 day growing season and therefore, the total amount of methane emitted from the rice crop is also dramatically reduced. Since a second potent greenhouse gas, nitrous oxide, can be emitted during the non-flooded period, emissions of this gas will also be measured using older and new state of the art measurement techniques to check whether this may need to be managed to minimize total greenhouse gas emissions from rice crops grown under alternative water saving irrigation practices.
These new growing practices are urgently needed to provide resilience for the rice industry facing future water scarcity in response to climate change.
Usually, rice is grown by flooding fields with water which blocks oxygen getting to the soil and allows bacteria to grow that breakdown and consume soil organic matter under anaerobic conditions. In doing so the bacteria let off a potent greenhouse gas called methane, most of which is released to the atmosphere from rice fields though the rice plants themselves. The plants have small air spaces in their roots and stems which are connected. Methane moves into the roots from the soil and travels up to the stems a bit like a straw, where it escapes from the plant into the air through tiny micropores on stem and leaf surfaces. Newer, drill sown rice growing practices, which use less water and are quite common in Australia, involve the farmer delaying the time at which the field is completely filled up with water for several weeks after planting. The seed is drilled directly into soil and then established by periodically flushing the field with irrigation water several times for several weeks until a few leaves have grown.
Since flushing is where the field is filled up with water and then drained within 12-24 hours, it allows the soil to remain in contact with the air and retain oxygen which prevents the special methane producing bacteria from being able to survive, no methane is produced and so none is available for release to the atmosphere from the rice field. Only after several weeks after planting and the first flush irrigation is applied, is the field completely filled with water.
The number of days that methane can be produced is reduced by 50 days or sometimes even more, over a 150 day growing season and therefore, the total amount of methane emitted from the rice crop is also dramatically reduced. Since a second potent greenhouse gas, nitrous oxide, can be emitted during the non-flooded period, emissions of this gas will also be measured using older and new state of the art measurement techniques to check whether this may need to be managed to minimize total greenhouse gas emissions from rice crops grown under alternative water saving irrigation practices.
These new growing practices are urgently needed to provide resilience for the rice industry facing future water scarcity in response to climate change.