Raised Bed Soil Care Tips: Water & the High Desert

If you’ve spent any time in a high-altitude desert like New Mexico, you know that you need to drink water more frequently than you would in a more humid environment to stay hydrated.  So does your soil! This isn’t to say you need to flood your garden beds every day (this can drown your plants!), but the key to maintaining optimal conditions for plant health is maintaining a consistent moisture level in the soil, which can be difficult in raised beds.  In New Mexico we face dual threats of water loss: sandy soils lead to quick water runoff, and high heat combined with our altitude creates a huge amount of evaporative loss. 

Here are some tips to maintaining a well-hydrated garden with thriving plants in New Mexico:

• Know when to water: there is no perfect schedule anyone can give you to achieve the perfect garden as each garden is its own tiny ecosystem with multiple issues affecting water retention.  Until you figure out the best schedule for your garden a simple trick is to stick your finger into the soil up to the second knuckle. It should be damp all the way down. If it’s dry or only slightly damp, it’s time to water.  You’ll quickly develop a schedule and start to notice other signs that will alert you to the soil conditions.
• Choose the right watering system. After you establish a watering pattern, you can set up a timer on your irrigation system to establish a consistent schedule. Drip irrigation is far and away the most efficient method to water your garden, but unless your drips are saturating the soil, you may be running into problems with consistent moisture throughout the grow area. Combine your drip irrigation with regular intervals of early morning or late evening deep manual watering, every 2-6 days depending on the weather.  As your plant’s roots spread out, they may run into dry spots away from the drip emitters, which can cause the roots to turn back in and stunt growth.  The dryer soil gets, the more it will repel moisture (sounds weird, but it’s called hydrophobia and is one of the reasons we have so much erosion and flash flooding in the desert).  Soaker hoses, as an alternative to drips, can help distribute water evenly across a row or bed in areas that are fully exposed to the sun.
• Should you water in the morning or evening? What about mid-day? It is best to water in the early morning or late evening for moisture retention but do your best to stay consistent- plants and soil are like cats- they don’t adapt well to sudden change. But sometimes life happens and you can’t stay on schedule. So, in the desert, water when you can.  Online garden advice will say watering in the morning will help prevent fungal diseases that can damage your plants, but most garden advice comes from people working in areas with a relative humidity above 30%.  In the desert, fungal disease is uncommon, and your plants will be happy to have water whenever they can get it. If you check your plants mid-day and they look a little sad, they’ll likely survive until the next scheduled watering, but a little pick-me-up won’t hurt.

• Add shade, practice polyculture & companion plant. Polyculture is what you are probably already doing in your beds- growing all sorts of different vegetables you like to eat, instead of just one type of vegetable per row or bed (monoculture). Not only will a diverse crop system help fight off pests, but it’s also a great way to create shaded areas for more delicate plants while your full sun plants thrive. For example, plant some more delicate plants beneath an A-frame trellis with climbing squash vine. You can also put up a simple shade structure and cover the very top with shade cloth- your plants will get sun most of the day but avoid the harshest midday rays.  Shaded soil will prevent evaporative loss, and shaded plants won’t lose as much water through transpiration (water loss through leaves).

• Mulch! MULCH! Oh yeah, and mulch. Evaporation leads to 7% loss of New Mexico’s water annually- and in the case of your garden it is the likeliest culprit for daily dry soil.  A layer 4 inches thick (or more!) of mulch will protect the soil for direct sun and prevent massive evaporative loss. 
  
  Raised beds will also lose water from drainage, so it can be helpful to lay down a mix of cardboard and organic material (like wood chunks or leaves or organic mulch) before you fill your beds with soil. Adding an absorptive layer will help reduce water runoff and can redistribute moisture evenly through the lower soil layers. For vegetable and flower gardens we always recommend our Forest Floor Mulch which has a touch of compost added to it to keep feeding your soil while protecting it from the sun.

Watering correctly is the biggest challenge New Mexico gardeners face, especially if you’ve grown comfortable with indoor potting soils.  Gaining an understanding of how plants react to mismanaged watering will help you catch issues before they become problems. A soil moisture meter can also come in handy, but don’t obsess over recommendations for the perfect soil moisture number, your plants will tell you when they are happy.

The first indicator your plants need water is drooping leaves combined with dry soil. Probably no damage done, but a little refresh will help. Yellow spots and stunted growth are the first dangerous indication of under-watering. 

These symptoms can be signs of other problems, but if they appear in early season before you’re watering schedule is stable, or during the hottest months, it’s likely a little extra water will get you back on track.  Sometimes young plants stunted from underwatering won’t recover, but often they’ll slowly grow out of it.  Crisp, dry leaves can be indicator of under-watering, but this also happens because of sunburn and older leaves low on the plant that naturally die off.

Over-watering can be harder to diagnose. At a glance, over-watered plants look a lot like thirsty plants: droopy leaves.  If you notice your plants are drooping no matter how much you water them, check the soil moisture at 6-8 inches.  A sure sign of overwatering is the leaf tips will appear soggy and limp or will roll up or under the leaf. If you notice your leaf tips look different from the rest of the leaf, too much water is the likely culprit.   

 A healthy, thriving soil will retain moisture better than a tired, depleted soil.  Amending your soil with compost and organic amendments will keep your soil thriving all season.  For midseason refresher bags of compost, worm castings, and organic amendments Soilutions has you covered to keep your soil healthy and productive all season long.