Soil physical properties and tomato yield and quality in alternative cropping systems

The Sustainable Agriculture Farming Systems (SAFS) Project has studied the transition to low-input and organic alternatives in California's Sacramento Valley. This project compares a 4-5 yr rotation of tomato (Lycopersicon esculentum Mill.), safflower (Carthamus tinctorius L.), corn (Zea mays L.), and wheat (Triticum aestivum L,) followed by double-dropped bean (Phaseolus vulgaris L,) in the conventional system and oat (Avena sativa L.)-purple vetch (Vicia benghalensis L.) in the low-input and organic systems. A conventional 2-yr rotation (tomato-wheat) is also studied. In 1997 and 1998, we evaluated the transition to alternative systems on soil bulk density, water holding capacity, infiltration and storage, water use efficiency, and 'Brigade' tomato yield and quality. No differences in laboratory determinations of soil bulk density and water holding capacity were found; however, in situ water holding capacity was highest in the organic system, lowest in the conventional 4-yr rotation and intermediate in the low-input and conventional 2-yr rotations. In 1998, infiltration during 3-h irrigations was 0.028 m(3) m(-1) for the conventional, and 0.062 m(3) m(-1) and 0.065 m(3) m(-1) for the low-input and organic systems, respectively. Similar results were observed in 1997, The alternative systems required more water per irrigation for uniform application, resulting in higher soil water content in the organic systems throughout 1998, Evapotranspiration was higher in the conventional systems in both years relative to other systems. Tomato yields did not differ among systems in either year. Fruit quality was highest in the conventional 4-yr system.