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How to waterHow to waterWater conservation Plants and waterOne key to success in the vegetable garden is to keep the soil moisture at a suitable level at all times. Under dry conditions plants will conserve water by closing the stomata (tiny pores that are usually found on the underside of leaves). When this happens the carbon dioxide in the air that is needed for photosynthesis and growth cannot enter the airspace within leaves, and the plants will just stand there and do nothing even if the weather is warm and sunny. If you garden in a region with a long growing season this may not be a major problem, but in Sweden the season is short and we cannot afford these lost days. Optimum moisture levels and tolerance to drought vary. Some vegetables recover well after a dry spell. This is often the case with root crops e.g. carrot and scorzonera, which just continue from where they stopped. For other vegetables drought may alter the course of development drastically, which often leads to fantastic decreases in productivity. Spinach will stop producing leaves and go for seed production. Blooms and emerging fruits of cucurbits wrinkle like raisins and fall of as the plants concentrate all their efforts on one or a few fruits. Too much water can also limit plant growth. In waterlogged soils air is prevented from circulating in the soil pores. Roots need air and oxygen for nutrient uptake. Even the absorption of water by roots may be reduced in very wet soils. The worst problem is the damage to roots that even a short period of water logging may cause when roots are suffocated.It can be quite difficult to detect moisture problems by looking at the plants. The stomata close and the course of development may change long before any obvious signs of wilting can be observed. When the soil is to wet plants may also look rather healthy long after the damage is done. Don't wait for visible signs of damage to appear. A much better method is to check soil moisture directly by digging a small pit. The upper three cm usually dries when the weather is sunny, but ten cm down the soil should be moist and cool. Top How to waterWhen you water your vegetables (and other plants) it's important to wet the whole root depth of the soil. If you water a little and often you will wet only the surface and encourage the formation of shallow root systems, which will make the plants more susceptible to drought. It will also be wasteful since much of the water will just evaporate into the air. If you are uncertain about how much to water - dig a pit after a few hours to study the result. I would usually give some 20 to 30 litres per sqm when I water my clay soil, but the amount to give depend on soil type. Sandy soil can hold less water than clay soils. If you have a sandy soil you should water less every time but more often. Otherwise there will be a risk of nutrient leaching as excess water will just percolate downwards in the soil and take valuable nutrients with it.You can test your equipment to see how much it gives per time period. Use it to fill a container of known volume and record the time. My equipment gives 20 litres per minute and I would normally water every sqm from 60 to 90 seconds. Under the vegetables section I give more detailed recommendations for individual vegetables. Here I only provide some rough guidelines.
Water conservationIf you have limited access to irrigation water - use mulch to reduce evaporation from the soil surface. Less evaporation from the soil surface means more water available to your plants. Also use an irrigation method that minimises evaporation. In this respect the worst you can do is to spray the water on your plants and soil at mid day. If you water in the evening much less of the water will be lost. Water trenches between rows and drip irrigation are even better because the foliage of plants is not wetted. You should also consider growing relatively drought tolerant plants.Top
vegetables@frideen.com Last major update 2004-12-10 Copyright© Anders Frideen |