Israel provided incentives for farmers to switch to drip irrigation, in which pipes with tiny holes provide small, precisely adjusted flows of water. Ideally, drip irrigation provides water at just the rate at which it can be absorbed by plant roots. Invented by the Israeli engineer Simcha Blass, it can use half or less of the water used in ordinary irrigation to nourish the same number of plants. At the same time, drip irrigation is one of those ideas that sounds simple but is hard to accomplish in practice. To exude water in regular amounts from the holes, the water pressure must be exactly the same down the entire length of the pipe, an engineering challenge; if the pipe is underground, which maximizes contact with roots, the holes must not be susceptible to clogging by dirt or being infiltrated by water-seeking roots. The first Israeli drip-irrigation firm was established in 1966; by the 1990s, the method was being used in about half of Israel's farms.