The Ultimate Guide to Soil Moisture

You need to get the right amount of water to crops at the right time. Water and nutrients are used most efficiently when your crops have access to the amount of water the crop needs and the soil can hold.

This article describes how to use the data provided by soil moisture probes to more effectively manage your farm. Observing and understanding the consequences of soil moisture fluctuations in your crops’ root zone will enhance your efforts to maximize yield and reduce wasted resources.This article will cover:

ConnectedCrops provides the latest advances in sensor technology, cellular connectivity, and mobile interfaces. You will have a whole new level of real-time visibility to what’s happening in your fields.

• higher yields
• better product quality
• improved plant vigour
• reduction in disease
• more effective use of water (water efficiency)
• reduced irrigation costs

Growers report that using soil moisture measurements has led to a 10% increase in yield. University case studies have demonstrated yield increased by more than 20% for some crops, as well as faster growing cycles by using soil moisture measurements effectively.

Volumetric Water Content (“VWC”) is a numerical measure of soil moisture. . It is expressed as a percentage or ratio of the amount of water held by the soil. For example, one cubic meter of soil with 30% VWC contains 0.3 cubic meter, or 300 liters, of water. You should expect VWC readings between 5% and 35% depending on your soil type.

Your ideal soil moisture level is between field capacity and wilting point.  Once you get more experience tracking soil moisture readings you will be able to narrow this down based on your soil type, crop type, growth stage etc.  To start with, here are some key definitions you should be familiar with:

Field Capacity: As much water as the soil can hold, 2 or 3 days after a heavy rainfall, when the soil is fully saturated. At this point, there is very little downward movement of soil water due to gravity and very little suction due to capillary action.

Permanent Wilting Point: The amount of water remaining in the soil when the plant wilts in a humid atmosphere. The water remaining in the soil is held tightly by soil particles, and plant roots cannot easily extract water.

Saturation: refers to a soil’s water content when practically all pore spaces are filled with water. When the soil is fully saturated, the water will run off quickly via available channels until levels reach field capacity.

Available Soil Water: The amount of water in the soil between field capacity and the permanent wilting point. Generally, overhead irrigation should start before soil reaches 50% of available soil water. Drip irrigation should start before soil reaches 80% of available soil water

The amount of water available to the plants depends on the texture of the soil, for example sandy soils retain much less water than loam soils. Loam soils are usually highly valued for their consistent crop production. Note that the greatest amount of crop available water is in the loam-to-silt loam texture.

The field capacity and permanent wilting points are shown in the table below for various soil textures. You don’t need to remember these levels, the ConnectedCrops mobile app automatically configures Field Capacity and Permanent Wilting Point based on the soil type that you specified when you configured your sensor.