Soils which are exposed to iterative wetting and drying in a tropical region, such as Singapore, are prone to develop hydrophobic coatings on the soil particles which results in hardness and water repellence. This condition limits the rate and capacity of water absorption, which leads to poor infiltration and water retention in soil. In these circumstances, water has tendency to either evaporate or run off instead of infiltrating into the soil, resulting in poor irrigation efficacy and water wastage. This problem can be further compounded by sloping terrain such as on mounds and on hillsides, where water is more likely to run off. These terrain will dry out quickly and requires additional irrigation, while the runoff collects in lower areas, creating wet spots that contribute to promoting soil compaction and encourage disease. Such phenomenon is detrimental to plant growth. A new formulation composed of surfactants and super-absorbent polymer dispersions, RetenSol, is createdto promote both soil wetting and moisture retention.The technology has been tested for a range of plant species and shown to improve the long-term water availability, serving as a mini water reservoir. During irrigation, the innovative formulation is able touptake large amount of water, and the locked water moleculeswould not easily evaporate and serve as a reservior that will release water during drought stress.
In this technology, each aqueous formulation is prepared with two main distinctive features viz. soil conditioner and water retention unlike the commercially available products. These formulations are tested on both soils in outdoor environment, as well as on plants in green houses with notable performances. Tests were also carried out on drought resistant and non-drought resistant species. The novelty of the technology used are listed below: Great variation in soil texture and components limited the performance of commercial soil conditioners available for local environment. Initial screening of surfactants has been carried out to develop the suitable soil conditioner for the Singapore tropical soil. To overcome the uneven distribution of existing hydrophobic components in natural soil and to handle extreme water repellence, a stronger hydrophobic coating (wax based emulsion) is used other than common octadecyltrichlorosilane (OTS). To save the labor demand to physically mix the common solid water retention granular agents, a new cost-effective aqueous-based water super-absorbent polymer particle dispersion suitable for spray is developed. To combine both soil conditioner and water retention features, and to overcome the high viscosity and low permeation speed of only commercially available liquid water retention product (ESPECK-L), a formulation of surfactants and water super-absorbent polymer particle dispersion are tuned in such a way that the final product has both functions with maximum solution stability. Both soil condition and plant growth evaluation experiments of the developed formulation are performed to meet the field application.
Newly developed formulations are evaluated based on the experiments carried out in different soils types and with and without plants. Tests were also carried with a wide spectrum of plant species. Along with the test formulations, two commercially available products (Label: Amgrow, ESPECK-L) are considered as the controls. Following are the major advantages and improvements of the new formulations compared to the commercial ones: Tissue culture experiments revealed that the newly developed soil conditioner showed lower toxicity than Amgrow towards model plant Arabidopsis thaliana, comparable wetting performance, working period length, while at the same time the cost is lower than the commercially available product. The water super-absorbent polymer particle dispersion can be tuned with various sizes and water absorption ratio, can achieving both comparable and better soil moisture level than ESPECK-L. The final formulation including both retention and soil conditioning functionalities is first reported, and this formulation will also reduce labour cost as the formulation is applied via normal watering process and it will lower watering frequency. Plants treated with new formulations exhibited improved growth and significantly increased biomass compared to commercial controls due to more moisture availability in rhizosphere.
Ease of use Improves water permeability through the soil Increase water uptake in the soil Extend water retention in the soil Enhance growth of horticulture species Environmentally safe and non-toxic