140
A study conducted on a rice–wheat cropping system in India over 4 years showed
greater yields of wheat where rice and wheat straw were incorporated compared to
where it was removed or burned (Gupta et al. 2007). In contrast, straw management
did not affect rice yields. A meta-analysis conducted in China showed that retention
of rice straw increased rice yields by 5.2%, but that the yield benefit increased with
duration of straw incorporation, i.e., time after repeated application (Huang et al.
2013). In a study in India, wheat grain yield was 13% greater when rice straw was
incorporated in the soil compared to when it was removed. A recent study in India
showed that cereal yields, i.e., rice, wheat, and maize, are greater where straw is
incorporated than where it is removed under a diversified cropping system and different combinations of tillage and crop establishment methods (Nandan et al. 2018).
While the rice yield increased from 3.0% to 8.2%, the yield benefits were greater for
maize and wheat, likely due to a combination of moisture conservation under upland
conditions and nutrient contribution from the incorporated straw.
8.6 Paddy Soil Degradation Associated with Straw Removal
While straw incorporation is labor-intensive and requires machinery for effective
mixing with the soil, especially where rice yields are high, straw burning has negative impacts on soil fertility and soil organic C (Prasad et al. 1999; Surekha et al.
2003). The heat and duration of fire; soil moisture, both at the time of burning and
during tillage; the time elapsed and climatic condition between burning and tillage;
and the chemical, physical, and biological properties of the soil will all influence the
change in soil properties resulting from burning rice straw. The impact of straw
burning on soil fertility accumulates over time. Ponnamperuma (1984) highlighted
the need to consider experimenting with duration when drawing conclusions about
the sustainability of straw burning. However, research indicates that the advantages
of burning are offset by the disadvantages, including nutrient loss, depletion of soil
organic C, and reduction in the presence of beneficial soil biota (Mandal et al. 2004).
Nonetheless, the ash from burning rice straw is rich in K and, thus, the practice of
straw burning resulted in recycling of K, but with a loss of N and P.
Potassium recycling is influenced by straw management since more than 80% of
the K taken up by rice is in straw (Dobermann and Fairhurst 2000). Consequently,
K deficiencies are common in soils where rice straw is removed. In a study conducted under rainfed conditions in Thailand, Whitbread et al. (2003) calculated
negative K and S balances when rice straw was removed. Similarly, straw management influences Si, which has been shown to be beneficial in rice growth. Si dynamics in the soil is affected by straw management (Seyfferth et al. 2013; Wickramasinghe
and Rowell 2006). For example, soil-available Si was low in Vietnam where crop
residues are removed from the fields while in the Philippines there is high availabilP. Chivenge et al.
A study conducted on a rice–wheat cropping system in India over 4 years showed
greater yields of wheat where rice and wheat straw were incorporated compared to
where it was removed or burned (Gupta et al. 2007). In contrast, straw management
did not affect rice yields. A meta-analysis conducted in China showed that retention
of rice straw increased rice yields by 5.2%, but that the yield benefit increased with
duration of straw incorporation, i.e., time after repeated application (Huang et al.
2013). In a study in India, wheat grain yield was 13% greater when rice straw was
incorporated in the soil compared to when it was removed. A recent study in India
showed that cereal yields, i.e., rice, wheat, and maize, are greater where straw is
incorporated than where it is removed under a diversified cropping system and different combinations of tillage and crop establishment methods (Nandan et al. 2018).
While the rice yield increased from 3.0% to 8.2%, the yield benefits were greater for
maize and wheat, likely due to a combination of moisture conservation under upland
conditions and nutrient contribution from the incorporated straw.
8.6 Paddy Soil Degradation Associated with Straw Removal
While straw incorporation is labor-intensive and requires machinery for effective
mixing with the soil, especially where rice yields are high, straw burning has negative impacts on soil fertility and soil organic C (Prasad et al. 1999; Surekha et al.
2003). The heat and duration of fire; soil moisture, both at the time of burning and
during tillage; the time elapsed and climatic condition between burning and tillage;
and the chemical, physical, and biological properties of the soil will all influence the
change in soil properties resulting from burning rice straw. The impact of straw
burning on soil fertility accumulates over time. Ponnamperuma (1984) highlighted
the need to consider experimenting with duration when drawing conclusions about
the sustainability of straw burning. However, research indicates that the advantages
of burning are offset by the disadvantages, including nutrient loss, depletion of soil
organic C, and reduction in the presence of beneficial soil biota (Mandal et al. 2004).
Nonetheless, the ash from burning rice straw is rich in K and, thus, the practice of
straw burning resulted in recycling of K, but with a loss of N and P.
Potassium recycling is influenced by straw management since more than 80% of
the K taken up by rice is in straw (Dobermann and Fairhurst 2000). Consequently,
K deficiencies are common in soils where rice straw is removed. In a study conducted under rainfed conditions in Thailand, Whitbread et al. (2003) calculated
negative K and S balances when rice straw was removed. Similarly, straw management influences Si, which has been shown to be beneficial in rice growth. Si dynamics in the soil is affected by straw management (Seyfferth et al. 2013; Wickramasinghe
and Rowell 2006). For example, soil-available Si was low in Vietnam where crop
residues are removed from the fields while in the Philippines there is high availabilP. Chivenge et al.