Introduction

This chapter tells why it is important to study soil–plant–water relations. Water is the most important substance necessary for food production. People depend upon plants for food, so the challenge of feeding a growing population is discussed. The human population growth curve, a logarithmic one, is presented. Rules of logarithms are then given. A calculation is done to show that the human population is limited by the productivity of the land. The calculation shows that it requires two square yards (16,700 cm(2)) to feed one person. The sigmoid plant growth curve is presented followed by a mathematical analysis of Blackman's compound interest law for plant growth. Finally, data from corn and soybean are analyzed to show that their growth rate is exponential. A biography of Napier, the inventor of logarithms, is given in the appendix.