Grey cloud cover and a light morning drizzle has taken the edge off the drying conditions in mid-summer Northland. Or so it appears. Once soil has become dry, it hardens and the soil pores which normally let water in shrink down and resist water penetration. The amount of time and water it takes to rehydrate soil depends on many factors, including soil type and depth, cultivation practises, slope, organic matter content and other considerations.
My method of delivering water to the soil is ‘home-made’, basic and a fair bit of work to manage. But it is matched to the garden soil conditions and is able to keep the gardens sufficiently watered in a drought if I start watering early enough. The usual flow of gravity fed spring water has become a trickle, so I prime my water pumps, give thanks to the little river running around the gardens, and start drawing water up the four-meter high river bank. I use an electric pump to power two portable sprinklers and also a petrol-powered pump.
I use the sprinklers on the smaller ‘kitchen garden’ and on seedlings. Water penetrates my garden soil well, due to the years I’ve spent building a good soil structure through effective cultivation and composting. This is in contrast to hard, compacted soil where water more readily runs off into the garden paths. At this time of year, and in drought conditions, I water each of these gardens thoroughly once every two weeks for established plants and twice per week for seedlings. This relatively infrequent watering works because I have cultivated deeply, the clay portion in my soil holds more water than soils with a lesser clay content, and the organic matter I have added through mulching and composting holds at least four times its volume in water.
I have increased cultivation depth with helpers over the years by using garden forks to lift and break up compacted garden soils before rotary hoeing. This also prevents a compacted layer of soil forming beneath the action of the rotating blades of the rotary hoe, allowing water and plant roots to penetrate deeper into the soil. And watering deeply encourages deeper rooting because plant roots sense where the water is and grow in that direction, thus coming into contact with additional nutrients deeper down.
On the 80 square meter field gardens, I use a larger petrol powered pump which delivers water from a home-made ‘soaker hose’ (a four-meter length of alkathene pipe with many holes drilled in it and blocked at the end). Even for big home gardens, 300 litres of water delivered to the garden each minute is a lot of water and needs to be controlled. Northland is now officially in drought and I am tempted to rev up the pump engine to stay ahead of the evaporation rate. It’s fun to watch the crickets and slugs get washed out of cracks in some of the less well conditioned gardens and into the beak of the thrush that knows my routine and follows me around. But too much water can be damaging, even on a gentle slope. I have seen gardens where little ‘rivulets’ of surface water flow has caused the silt to separate from the other soil particles and be deposited into little alluvial fan shapes which are sort of pleasing to look at, but not ideal for garden soil.
And don’t forget about your work force in the soil, the soil life (worms, beneficial bacteria, fungi, etc.). Like us, they all need oxygen to live and don’t like being submerged or flooded. Like us, they thrive in a stable environment, with food, sufficient water and shelter (the spaces between the soil particles). This is what we, as Kiwi Gardeners strive to provide, drought or no drought.