Nitrates,water and salt: maintaining the fertility of agriculture

Abstract

The fertility of the soil depends on an ample supply of nitrogen compounds and on a variety of other nutrients and trace elements. The supply of nitrates by natural means has posed a limit to productivity since the inception of agriculture, and the avoidance of soil salination has been a necessity in many environments. Since the invention of an industrial process for fixing atmospheric nitrogen (the Haber process), there has been an ample supply of nitrates in the form of chemical fertilisers, capable of sustaining agriculture worldwide, and enabling it to feed the burgeoning human population. The growth in agricultural supply has been attributable, in the second half of the twentieth century, to the combined agency of hybrid crop species, chemical fertilisers and irrigation. Now, at the beginning of the twenty-first century, the problem of soil salination is limiting this growth and threatening to reverse it.