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

Chlorophyll content of maize leaf was reduced significantly at drought stress conditions. Chlorophyll a content varied significantly with different doses of biochar under drought conditions (**Table 4**).

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 conditions.


#### **Table 4.**

*Effect of rice husk biochar on chlorophyll content in 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

**Water saturation deficit (%)**

> **40% of FC**

**Control 60% of FC**

 66.9bc 63.7bc 62.2c 33.1a–c 36.2ab 37.7 a 1.9ab 1.9a 2.0a 71.2bc 70.2a–c 66.4bc 28.8a–c 29.7a–c 33.5a–c 1.8a–d 1.8a–c 1.9a 76.8bc 75.7a–c 72.8a–c 23.1a–c 24.3a–c 27.1a–c 1.7a–d 1.7a–d 1.8a–d 83.3a 79.8ab 78.3bc 16.6c 20.1bc 21.1a–c 1.5d 1.5cd 1.6b–d

CV (%) 14.1 36.8 10.7

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

**Water uptake capacity**

**40% of FC**

**Control 60% of FC**

**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.

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

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

biochar increased tissue water status of maize in sandy soil.

**Relative water content (%)**

> **40% of FC**

**Control 60% of FC**

*Figure having similar letter did not vary significantly.*

**Biochar doses (t/ha)**

*Maize - Production and Use*

**Table 3.**

**Figure 3.**

**64**

*of significance.*
