Salt Damage to Peppers Can Be Managed through Irrigation

Q. We are small farmers owning 2 acres of land in
India, We have just seen your opinion on RO water for horticulture crops. We are
growing roses and colour capsicum under poly greenhouse cultivation. Our ground
water electrical conductivity level (salinity) is too bad that it comes to 1.8. So our
plants came to death condition. We heard about reverse osmosis system and fixed
it to our farm. By this system leaves shrinkage and nutrient deficiency had
risen. So we are pleasing to suggest your idea about it. We are looking for your
grateful suggestion.

A. Pepper plants are very tolerant of this level of salinity. It only becomes a problem if we let the soil becomes excessively dry or if the drainage of the soil is very poor and the water drains slowly. Improve the drainage of the soil and irrigate so that the soil never dries to less than 60% of its water content. With a little bit of experience, you can determine this just using your hands and feeling the moisture content by squeezing it and using your fingers.

The kind of salts that you have in the soil will dictate if you were to use soil additives such as gypsum or not to help flush the salts from the soil. Sending a soil sample to a soils laboratory to determine which salts are present would be very helpful.

Generally speaking we start to see yield reduction in
pepper at about 1.5 dS/m (mmhos/cm). You are close to that threshold at 1.8. I
think you would only need to dilute your irrigation water maybe 20% with RO
water to get below this threshold.

New Mexico’s advice on salt damage to peppers

Another option is to water with your
irrigation water and then flush salts using an irrigation cycle using water
with lower salts. Use these in an irrigation cycle of salts/low salts/salts/low
salts/etc.

Monitor your drainage water for salt content. Monitoring
your drainage water and recording it regularly will help you with managing
salts (flushing, etc.)

Two types of salt damage occurs to plants; one is due to
total salts (EC) and the other is due to the type of salts (specific ion
effect). Particularly damaging are sodium, chloride and boron. If these salts
are involved then this might mean a very different problem than just salts in
general.

What to do?

• If it is possible, determine which salts are present and
  not just the level of salinity (1.8). 
• When irrigating never let the soil or
  substrate dry out too much. 
• With high salts you should be irrigating frequently
  with a smaller volume of water. This prevents the salts from becoming too
  concentrated. 
• If you can over irrigate and flush salts from your soils make
  sure you over irrigate by about 20% to keep salts moving through your soil
  profile and maintain a steady state of salts and prevent the buildup of salts.

Depending on the type of salts in your irrigation water
you will see different nutrient deficiencies.

Note: This question was from farmers in India. Potable water, water in the Las Vegas Valley coming from the tap, is close to this level of salinity or salts. This is because a large percentage of this water comes from the Colorado River unless you are on well water. Salt levels of our native soils here in the Las Vegas Valley are 25 times this level. Water management is very important to control salinity.