**2.5 Effect of rice husk biochar on relative water content (RWC), water uptake capacity (WUC), and water saturation deficit (WSD) in maize under drought stress**

Relative water content of maize plant was reduced significantly at drought stress conditions because of low water content of soil. Application of rice husk biochar at different doses helped to increase water-holding capacity of soil under drought conditions and thereby increased relative water content of maize plant (**Table 3**). Under control condition (80% of FC), 60% of field capacity, and 40% of field capacity, highest RWC of maize were 83.37, 79.86, and 78.32%, respectively, when biochar was applied at 20 t/ha, and lowest RWC of maize were 66.93, 63.75, and 62.25%, respectively, when no biochar was applied.

Water saturation deficit of maize plant was increased significantly at drought stress conditions, and it is varied with different doses of biochar under drought conditions (**Table 3**).Under control condition (80% of FC), 60% of field capacity, and 40% of field capacity, lowest WSD of maize were 16.6, 20.1, and 21.1%, respectively, when biochar was applied at 20 t/ha, and highest WSD of maize were 33.0, 36.2, and 37.7%, respectively, when no biochar was applied.

Water uptake capacity of maize plant was increased significantly under drought stress because soil contained low moisture to be uptaken by plant. WUC depended

**Figure 2.** *Effect of rice husk biochar on days to maturity of maize under drought conditions. Bar indicates LSD at 5% level of significance.*


1.5 g/hr., respectively, when biochar was applied at 20 t/ha, and lowest exudation rates of maize were 1.1, 1.0, and 0.7 g/hr., respectively, when no biochar was applied. Similar result was observed by [32]. [33] found biochar application increased water retention capacity of soil. [34] reported application of biochar increased water-holding capacity of field-grown wheat and exudation rate.

*Amelioration of Drought Tolerance in Maize Using Rice Husk Biochar*

**2.7 Effect of rice husk biochar on chlorophyll contents of maize under drought**

Chlorophyll content of maize leaf was reduced significantly at drought stress conditions. Chlorophyll a content varied significantly with different doses of

Under control condition highest chlorophyll a (1.4 mg/g) was found when biochar was applied at 20 t/ha, and it was lowest (1.2 mg/g) when no biochar was applied. Under 60% of field capacity, highest chlorophyll a (1.4 mg/g) was found when biochar was applied at 20 t/ha, and it was lowest (1.1 mg/g) when no biochar was applied. Under 40% of field capacity, highest chlorophyll a was observed when plant was treated with biochar at 20 t/ha (1.3 mg/g), and it was lowest (1.1 mg/g) when no biochar was applied. Chlorophyll b increased with the application of biochar under drought stress conditions, although it was insignificant (**Table 4**). Under control condition highest chlorophyll b (1.1 mg/g) was found when biochar was applied at 20 t/ha, and it was lowest (0.9 mg/g) when no biochar was applied. Under 60% of field capacity, highest total chlorophyll b (1.0 mg/g) was found when biochar was applied at 20 t/ha, and it was lowest (0.9 mg/g) when no biochar was applied. Under 40% of field capacity, highest chlorophyll b was observed when plant was treated with biochar at 20 t/ha (1.0 mg/g), and it was lowest (0.9 mg/g) when no biochar was applied. Under control condition highest total chlorophyll (2.0 mg/g) was found when biochar was applied at 20 t/ha, and it was lowest (1.5 mg/g) when no biochar was applied. Under 60% of field capacity, highest total chlorophyll (1.7 mg/g) was found when biochar was applied at 20 t/ha, and it was lowest (1.4 mg/g) when no biochar was applied. Under 40% of field capacity, highest total chlorophyll was observed when plant was treated with biochar at 20 t/ ha (1.6 mg/g), and it was lowest (1.3 mg/g) when no biochar was applied. [39] marked reduction in chlorophylls in wheat cultivars subjected to water stress. [35] reported that biochar increased chlorophyll content in milk thistle under drought

**stress**

conditions.

**Table 4.**

**65**

**Biochar doses (t/ha)**

**Chlorophyll a (mg/g fresh weight)**

> **40% of FC**

**Control 60% of FC**

*Figure having similar letter did not vary significantly.*

**Chlorophyll b (mg/g fresh weight)**

> **40% of FC**

**Control 60% of FC**

 1.2c–e 1.1de 1.1e 0.9a 0.9a 0.9a 1.5ab 1.4ab 1.3b 1.2c 1.2de 1.2c–e 1.0a 0.9a 0.9a 1.5ab 1.5ab 1.4ab 1.2c 1.2cd 1.2c–e 1.0a 1.0a 0.9a 1.9ab 1.5ab 1.5ab 1.4a 1.4ab 1.3bc 1.1a 1.0a 1.0a 2.0a 1.7ab 1.6ab

CV (%) 6.1 3.3 2.3

*Effect of rice husk biochar on chlorophyll content in maize under drought conditions.*

**Total chlorophyll (mg/g fresh weight)**

> **40% of FC**

**Control 60% of FC**

biochar under drought conditions (**Table 4**).

*DOI: http://dx.doi.org/10.5772/intechopen.88824*

#### **Table 3.**

*Effect of rice husk biochar on RWC, WSD, and WUC of maize under drought conditions.*

on water-holding capacity of soil, and it was varied with different doses of biochar under drought condition (**Table 3**). Under control condition (80% of FC), 60% of field capacity, and 40% of field capacity, lowest WUC of maize were 1.5, 1.5, and 1.6, respectively, when biochar was applied at 20 t/ha, and highest WUC of maize were 1.9, 1.9, and 2.0, respectively, when no biochar was applied. [29] reported biochar increased water-holding capacity. [30] found that biochar increased RWC and water use efficiency of drought-stressed tomato plants. [31] also reported that biochar increased tissue water status of maize in sandy soil.

## **2.6 Effect of rice husk biochar on exudation rate of maize under drought stress**

Exudation rate of maize plant was reduced significantly at drought conditions. Exudation rate depends on available water in soil to be uptaken by the plant. Exudation rate of maize varied due to different doses of biochar under drought conditions (**Figure 3**). Under control condition (80% of FC), 60% of field capacity, and 40% of field capacity, highest exudation rates of maize were 2.3, 1.5, and

#### **Figure 3.**

*Effect of rice husk biochar on exudation rate of maize under drought conditions. Bar indicates LSD at 5% level of significance.*

*Amelioration of Drought Tolerance in Maize Using Rice Husk Biochar DOI: http://dx.doi.org/10.5772/intechopen.88824*

1.5 g/hr., respectively, when biochar was applied at 20 t/ha, and lowest exudation rates of maize were 1.1, 1.0, and 0.7 g/hr., respectively, when no biochar was applied. Similar result was observed by [32]. [33] found biochar application increased water retention capacity of soil. [34] reported application of biochar increased water-holding capacity of field-grown wheat and exudation rate.
