Plant-Water Relationships

Urban growth, intensive agricultural production and environmental concerns exert increased demand for available water. Therefore there is an increasing awareness of the need to manage irrigation correctly in order to optimize the quality and yield of the produce, minimize input costs and avoid adverse environmental impacts.

Getting the most from an irrigation system requires accurate scheduling of water application and a sound understanding of a plant’s soil-water relationship. 

 

Water is essential for the growth processes of a plant for a number of reasons. Water transports minerals and nutrients that are absorbed by a plant’s root system. Water is also the principle medium for chemical processes that support plant metabolism. Evaporation between intercellular spaces provides a cooling mechanism that allows plants to maintain favorable temperatures necessary for metabolic processes. In addition water also provides physical support for plants. (Tugor Pressure). Well-watered plants maintain their shape due to this internal pressure in plant cells. Loss of this pressure due to insufficient water supply can be noticed as plant wilting.

Figure 1 .... 

The major consequence of insufficient water is yield reduction. When too little water is available in the root zone, the plant will reduce the amount of water lost through transpiration by partial or total stomatal closure. This results in decreased photosynthesis since CO2 required for this process enters the plant through the stomata. Decreased photosynthesis reduces biomass production and results in decreased yields.

Soil-Water relationships

Soil is not essential for plant growth and indeed plants can be grown hydrophonically (in a liquid culture). However, plants are usually grown in soil and soil properties directly affect the availability of water and nutrients to the plants. Soil is composed of solid particles, water and air. It is important to understand the interactions between soil and water, and soil water tension. The percentage of these components varies with soil texture and structure.

graph_soil_water.gif

Soil water affects plant growth directly through its controlling effect on plant water status and its effect on aeration, temperature and nutrient transport. Soil water is usually measured in terms of water content as percentage by volume or mass and indicates the amount of water stored in the soil at any given time. Water content is the relative amount of water in the soil and does not indicate the available water to the plant. Therefore soil water content and soil water potential should both be considered when dealing with plant growth and irrigation.  

Water available to plants lays between field capacity (FC) and the permanent wilting point (PWP). The soil is at field capacity when all the gravitational water has been drained and a vertical movement of water due to gravity is negligible. The permanent wilting point is defined as the point where there is no more water available to the plant. It is therefore necessary to irrigate before the plants are stressed to a point of wilting.

Because the Floppy system is so versatile it is possible to irrigate more frequently and at regular intervals in order to prevent plants experiencing stress conditions.  The system is easy to manage and by applying appropriate scheduling using the Floppy yields can increase with up to 40 %.

The system was independently tested by the SA Institute for Agricultural Engineering, confirming dramatic water and energy savings compared to conventional irrigation systems. This is partly due to the fact that the sprinkler makes uniform droplets with no mist formation resulting in a 30% water saving. The medium sized droplets do not compact the soil.

The Floppy Sprinkler has a fitted flow controller that ensures super accurate irrigation even on slopes that effects the infiltration of water into the soil. 

Another advantage of the Floppy system is that it enables the farmer to regulate plant temperatures through crop cooling.

At the end of the day it  boil downs to when it comes to making good irrigation and planting decisions one must first have an understanding of the soil-water and plant interactions.