Biochar with Alternate Wetting and Drying Irrigation: A Potential Technique for Paddy Soil Management

Abstract

Over half of the world’s population depends on rice for its calorie supply, although it consumes the highest amount of water compared to other major crops. To minimize this excess water usage, alternate wetting and drying (AWD) irrigation practice is considered as an efficient technique in which soil intermittently dried during the growing period of rice by maintaining yield compared to a flooded system. Continuous AWD may result in poor soil health caused by carbon loss, nutrient depletion, cracking, and affecting soil physical properties. Due to being a potential organic amendment, biochar has a great scope to overcome these problems by improving soil’s physicochemical properties. Biochar is a carbon enriched highly porous material and characterized by several functional groups on its large surface area and full of nutrients. However, biochar’s implication for sustaining soil physicochemical and water retention properties in the AWD irrigation systems has not been widely discussed. This paper reviews the adverse impacts of AWD irrigation on soil structure and C, N depletion; the potential of biochar to mitigate this problem and recovering soil productivity; its influence on improving soil physical properties and moisture retention; and the scope of future study. This review opined that biochar efficiently retains nutrients and supplies as a slow-release fertilizer, which may restrict preferential nutrient loss through soil cracks under AWD. It also improves soil’s physical properties, slows cracking during drying cycles, and enhances water retention by storing moisture within its internal pores. However, long-term field studies are scarce; additionally, economic evaluation is required to confirm the extent of biochar impact.

A Review on Current Status of Biochar Uses in Agriculture

“…As an example, the potassium found within biochar is available for plant uptake [23]. Biochar can also have a variety of effects on soil pH, the degree to which is often dependent on the feedstock and production conditions [33]. There are several species of microbes (acidobacteria, nematodes and fungi such as mycorrhizae) found within soils [4].…”

“…For example, the potassium that is present in biochar from its original feedstock is generally found in forms available for plant uptake [23]. As can be seen in Figure 3, whether pH increases or decreases after biochar amendment depends on the characteristics of the biochar [33]. Generally, biochars formed from agricultural residues tend to be more alkaline and therefore help increase the pH of soils [23].…”

“…The effects of biochar on crop yields is also a fundamental benefit that overall aids in protecting the environmental system [42]. As seen in Figure 4, biochar can not only reduce CO 2 emissions but also reduce nitrous oxide [33,72]. If food producers can increase crop yields within current crop land area and without expanding agricultural lands, this helps protect current forested land [42].…”

Rice Growth Performance, Nutrient Use Efficiency and Changes in Soil Properties Influenced by Biochar under Alternate Wetting and Drying Irrigation

“…Application of wood biochar and bamboo biochar significantly increase the pH of acidic soil [37]. The ability of biochar to improve soil acidity was also reported in many studies [38,39]. Biochar shows a different mechanism to control soil pH due to its unique surface chemistry and various functional organic groups and compounds [40].…”

Combined Use of Biochar with 15Nitrogen Labelled Urea Increases Rice Yield, N Use Efficiency and Fertilizer N Recovery under Water-Saving Irrigation

“…However, biochar can also influence soil moisture retention by changing several soil physical parameters such as bulk density, porosity, aggregate stability, cracking, etc. [66]. According to Chen et al [67], the addition of rice straw and rice husk biochar improved the moisture content of sandy loam and silty loam soil up to 18.61% and 19.66%, respectively.…”