The more organic matter in the soil the better it retains moisture. Each 1% of organic matter in the soil will retain 168,000 litres per hectare. That’s of course hard to visualise. What it means is 4 cubic meters for a standard 10 pole allotment or 14 kilos per square meter. So 5% organic matter in the soil will hold 70 kilos of water per square meter. Substantially more than the body weight of a model like Kate Moss.