Potato farms in the country use different levels of mechanization. Each farm also has access to different qualities of irrigation water and types of soil. Given these varying factors in productivity, previous studies identified the most vital factors as the soil quality, irrigation water quality, and variety of potato.
The irrigation water quality has the greatest effect. The presence of chemicals such as sodium can greatly influence the soil and the growth of the potato, thereby affecting the crop yield and the size of the tubers.
Using irrigation water with the right characteristics will improve the effectiveness of preparing the field for planting potatoes. Researchers from the King Saud University (KSU) took it upon themselves to come up with the SWQI. (Related: Cultivated for more than 10,000 years, sweet potatoes have out-lived many civilizations they helped nourish.)
The researchers chose the Spunta variant of potato. They then studied the effect of different irrigation water qualities and soil textures on the following traits: Crop yield, the efficiency of water usage, the tuber modulus of elasticity (also known as the tensile properties of the potato tuber), and the tuber shape index.
The irrigation water qualities that they examined were sodium adsorption ratio (SAR), electric conductivity (EC), and their pH level. Meanwhile, the soil qualities that they evaluated were the SAR, EC, pH level, the percentage of organic matter present, and the soil texture index.
They determined potato yield by harvesting tubers from selected plants, measuring them, and calculating the number that would have been produced per hectare. This value was then used to compute the water use efficiency of the irrigation system.
They also performed field evaluations of the center pivot sprinkler irrigation system, the most commonly used means of irrigation in Saudi Arabia. Last but not the least, they determined the shape of the tuber based on the length, width, and thickness of individual specimens, as well as elasticity.
Based on the soil and water quality index that they compiled, the researchers determined that the yield and properties of Spunta potatoes in center pivot irrigation systems ranged from a low of 21.72 percent to a high of 79.63 percent. The relationship between the SWQI and the crop yield appeared to be quadratic.
Furthermore, raising the SWQI led to crops with lower yields. This might be due to increasing amounts of salt as the water increases. Higher amounts of salt reduce the number of tubers per plant.
As the SWQI went up, the shape index also went down. Potatoes tended to be long or very long. An increase in SWQI also led to linear increases in the tensile properties of tubers, as well as a corresponding rise in the efficiency of water use.
Last but not least, they also determined that potato plants of the Spunta variety can tolerate saline water-related stress in the loamy sand soil that is prevalent throughout Saudi Arabia.
The KSU researchers believe their soil and water quality index can serve as a powerful tool to predict the effects of different kinds of input on the crops, especially if it can be applied on the regional scale.
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