Impact of Hydrogels on Early Growth of Maize in Sandy Regosols: Progress towards Improving Growth Performance by Enhancing Water and Nutrients Retention Capacity of the Soil

Super Absorbent Polymers or hydrogels are known for enhancing the water-holding properties of soils. This experiment was conducted to evaluate the influence of four different locally-produced hydrogels and one commercially available hydrogel on the early growth of maize in sandy Regosols. Maize variety, Pacific 984 was tested with six treatments in Randomized Complete Block Design. T1 - Reference hydrogel (Sodium polyacrylate-based), T2 - Acrylic acid and acrylamide-based hydrogel where urea has incorporated chemically (g/g), T3 - without urea incorporating to the hydrogel used in T2, T4 - similar to T2, but urea incorporated only up to 6.17% (g/g), T5 - agriculture grade commercial hydrogel (Potassium polyacrylate-based) and T6 - control (without hydrogel) were used for the study. Soil properties and plant growth parameters were quantified. A significant difference was observed in soil pH, total N and available P among treatments after one month of application. Treatment 2 showed the highest total N (0.19%) while T4 showed the highest P (18.94 ppm). The highest growth performances were given by locally produced hydrogels over commercial hydrogel and control treatments. Treatment 2 recorded the highest leaf area (1153.3 cm 2 /plant), plant height (128.90 cm) and total dry mass production (49.36 g/plant) while T4 has recorded the highest stem girth (4.87 cm). It was observed that locally produced hydrogels including the hydrogel without incorporating urea, have given superior performance over commercial hydrogels. Therefore, it can be concluded that locally produced hydrogel-formulations can enhance the growth of maize effectively than imported commercial hydrogels.

*indikaherath@wyb.ac.lk https://orcid.org/ 0000- 0002-7630-9894 This article is published under the terms of the Creative Commons Attribution 4.0 International License which permits unrestricted use, distribution and reproduction in any medium provided the original author and source are credited.
(g/g), T3 -without urea incorporating to the hydrogel used in T2, T4 -similar to T2, but urea incorporated only up to 6.17% (g/g), T5 -agriculture grade commercial hydrogel (Potassium polyacrylate-based) and T6 -control (without hydrogel) were used for the study. Soil properties and plant growth parameters were quantified. A significant difference was observed in soil pH, total N and available P among treatments after one month of application. Treatment 2 showed the highest total N (0.19%) while T4 showed the highest P (18.94 ppm). The highest growth performances were given by locally produced hydrogels over commercial hydrogel and control treatments. Treatment 2 recorded the highest leaf area (1153.3 cm 2 /plant), plant height (128.90 cm) and total dry mass production (49.36 g/plant) while T4 has recorded the highest stem girth (4.87 cm). It was observed that locally produced hydrogels including the hydrogel without incorporating urea, have given superior performance over commercial hydrogels. Therefore, it can be concluded that locally produced hydrogel-formulations can enhance the growth of maize effectively than imported commercial hydrogels.

INTRODUCTION
The consequences of climate change on agricultural production are getting aggravated. Food production is in crisis due to prolonged drought conditions in the world with recent climate change (Falkenmark, 2013

Analysis of Soil Properties
Soil pH and Electrical Conductivity were measured by using a glass electrode/pH meter and conductivity meter and cell, respectively. Walkley and Black method (Nelson and Sommers,1982) was applied to determine Soil Organic Carbon as cited in Dharmakeerthi et al. (2007). Total Nitrogen in soil was determined by using the Kjeldahl method (Bremner and Mulvaney, 1982) while the Olsen method (Olsen et al.,1954) was used to quantify the available Phosphorus in the soil as cited in Dharmakeerthi et al. (2007).

Analysis of Soil Properties
The soil pH level for maize should usually be close to neutral or slightly acidic for better plant growth. This sandy soil had a pH level of 7.11 before the application of treatments (Table 3).
It could be observed that the soil pH was ranged from 7.23 to 7.53 among treatments and showed a significant difference after one month of treatment application. The lowest pH was recorded by T1(7.23) while the highest pH was given by control (7.53). All treatments showed an increment in soil pH compared to the initial status.
However, soil pH level was still in the favourable range for maize cultivation (Table 4).   (Wiatrak et al., 2009). According to the initial analysis, this sandy soil showed 134.3 µs/cm of EC (Table 3). However, the Electrical Conductivity of soil has been reduced after one month of application. This may be due to the absorption of nutrients from the soil by plants.
Electrical conductivity was varied between 68.63 (µs/cm) to 75.93 (µs/cm) and the highest EC was given by T4 while the lowest was given by T1 (Table   4). There was no significant difference in EC among treatments when tested after the application of hydrogels.
Nitrogen plays a vital role in plant nutrition. The soil used for the experiment had a very low level of total N (  (Figure 1 and Table 5).
When considering stem girth, a significant difference could be observed at 9 th week. T4 and T2 showed a higher girth while T6 showed the least girth value than all other treatments (Table   5).   (Table 5).
When leaf area increases, it tends to intercept more light and it enhances the photosynthetic potential (Weraduwage et al., 2015). According to the results, Treatment 2 ( Figure 2) and Treatment 4 showed leaf area than other treatments. However, Treatment 5 and control accounted for the lowest leaf areas (Table 5).
When considering the plant dry matter, the highest mean value of the total dry mass production (49.36 g) was observed in T2. The dry matter content in T2 and T4 was significantly higher than in others. T6 showed the lowest mean value (