141
ity due to crop residue retention (Settele et al. 2018). Removal of rice straw from the
field has been practiced widely in South Asia and has been associated with K and Si
deficiencies influencing rice productivity (Wickramasinghe and Rowell 2006).
Removal of rice straw from the field can cause numerous direct and indirect adverse
impacts on the ecosystem including depletion of soil organic C. Important direct
impacts of removal are low input of C biomass, reduction in nutrients/elemental
cycling and decrease in food/energy source for soil biota along with the attendant
decline in soil quality (Vijayaprabhaka et al. 2017).
8.7 Constraints, Trends, and Recommendations
Increasingly, rice straw is incorporated in fields where rice is grown. This is more so
with the increasing use of combine harvesters that leave all the crop residues in the
field compared to the traditional manual harvesting where only a portion of the
straw was retained in the field. There are benefits associated with the incorporation
of rice straw in the soil, including greater yields, nutrient cycling, soil organic matter build-up, and a general benefit on ecosystem services. However, there is a need
to consider timing of application and water management to maximize the benefits
of straw in the soil and reduce the negative effects such as production of GHG emissions or release of phenolic compounds that affect nutrient availability. This brings
into question the practicality of straw incorporation on intensive systems, e.g., triple
rice cropping where there is little time between crops to allow for aerobic decomposition. This suggests that solutions for straw management need to be tailored to suit
farmer conditions. In situations where triple rice cropping is mechanized, there is a
need to consider cost-effective alternatives to straw management with documentation of the experiences to enable extension workers to give informed recommendations to farmers.
In cases where combine harvesters are used, leaving large quantities of rice residue in the field, the practice of zero tillage with the use of seed drills is affected by
residues clogging the machinery. Alternative equipment should be considered.
There is also a need for studies to determine proportions of straw that can be left on
the field with minimum effects on land preparation and establishment of the next
crop. Options for collection of straw from the field, especially where combine harvesters are used, have been discussed elsewhere in this book, but decisions on
whether to collect or leave straw in the field need to take into consideration the
trade-offs of the different options. Nonetheless, there are benefits, in general, of
returning rice straw to the field for sustainable cycling of nutrients and improving
crop yields.
8 Rice Straw Incorporation Influences Nutrient Cycling and Soil Organic Matter
ity due to crop residue retention (Settele et al. 2018). Removal of rice straw from the
field has been practiced widely in South Asia and has been associated with K and Si
deficiencies influencing rice productivity (Wickramasinghe and Rowell 2006).
Removal of rice straw from the field can cause numerous direct and indirect adverse
impacts on the ecosystem including depletion of soil organic C. Important direct
impacts of removal are low input of C biomass, reduction in nutrients/elemental
cycling and decrease in food/energy source for soil biota along with the attendant
decline in soil quality (Vijayaprabhaka et al. 2017).
8.7 Constraints, Trends, and Recommendations
Increasingly, rice straw is incorporated in fields where rice is grown. This is more so
with the increasing use of combine harvesters that leave all the crop residues in the
field compared to the traditional manual harvesting where only a portion of the
straw was retained in the field. There are benefits associated with the incorporation
of rice straw in the soil, including greater yields, nutrient cycling, soil organic matter build-up, and a general benefit on ecosystem services. However, there is a need
to consider timing of application and water management to maximize the benefits
of straw in the soil and reduce the negative effects such as production of GHG emissions or release of phenolic compounds that affect nutrient availability. This brings
into question the practicality of straw incorporation on intensive systems, e.g., triple
rice cropping where there is little time between crops to allow for aerobic decomposition. This suggests that solutions for straw management need to be tailored to suit
farmer conditions. In situations where triple rice cropping is mechanized, there is a
need to consider cost-effective alternatives to straw management with documentation of the experiences to enable extension workers to give informed recommendations to farmers.
In cases where combine harvesters are used, leaving large quantities of rice residue in the field, the practice of zero tillage with the use of seed drills is affected by
residues clogging the machinery. Alternative equipment should be considered.
There is also a need for studies to determine proportions of straw that can be left on
the field with minimum effects on land preparation and establishment of the next
crop. Options for collection of straw from the field, especially where combine harvesters are used, have been discussed elsewhere in this book, but decisions on
whether to collect or leave straw in the field need to take into consideration the
trade-offs of the different options. Nonetheless, there are benefits, in general, of
returning rice straw to the field for sustainable cycling of nutrients and improving
crop yields.
8 Rice Straw Incorporation Influences Nutrient Cycling and Soil Organic Matter