ABSTRACT
Food and water security and sustainable development have been a major concern around the world. However, the results of worldwide studies of land and water use, along with their ecological impacts, lead to three constraints that will narrow the range of possible alternatives to increase food production sufficiently to meet global demand (Sposito 2013): (1) land conversion for crop cultivation is nearing its planetary limit, (2) use of blue water (i.e., liquid water in rivers, lakes, wetlands, and aquifers) by farmlands is also nearing its planetary limit, and (3) most of the water consumed by farmlands is green water (i.e., soil water held in the unsaturated zone and available to plants). Among these three constraints, the first one is related to limited land availability, the second one is linked to limited agricultural water availability, and the third one reveals an important facet of cropland water use. Feeding an additional 3.3 billion people by 2050 and at the same time eradicating malnutrition would require an additional 5600 km3 per year in consumptive water use (Falkenmark and Rockström 2004). However, where this water will come from is hardly clear. It is becoming
15.1 Introduction .......................................................................................................................... 373 15.2 Soil-Specific Farming: Nonirrigation Field Measures ......................................................... 378
15.2.1 Rainwater Harvesting ............................................................................................... 378 15.2.2 Soil Cover and Surface Treatment ............................................................................ 378 15.2.3 Soil Tillage ................................................................................................................ 379
15.3 Soil-Specific Irrigation Measures .........................................................................................380 15.3.1 Advantages and Function of Precision Irrigation ..................................................... 381 15.3.2 Components of Soil-Specific Irrigation .................................................................... 381
15.3.2.1 Field Scouting and Management Zones ..................................................... 383 15.3.2.2 Soil Sampling or Monitoring ..................................................................... 383 15.3.2.3 Variable Rate Technology ..........................................................................384 15.3.2.4 Irrigation Controller ...................................................................................384
