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 es culentum Mill.), safflower (Carthamus tinctorius L.), corn (Zea mays L.), a nd wheat (Triticum aestivum L,) followed by double-dropped bean (Phaseolus vulgaris L,) in the conventional system and oat (Avena sativa L.)-purple ve tch (Vicia benghalensis L.) in the low-input and organic systems. A convent ional 2-yr rotation (tomato-wheat) is also studied. In 1997 and 1998, we ev aluated the transition to alternative systems on soil bulk density, water h olding capacity, infiltration and storage, water use efficiency, and 'Briga de' tomato yield and quality. No differences in laboratory determinations o f soil bulk density and water holding capacity were found; however, in situ water holding capacity was highest in the organic system, lowest in the co nventional 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 obse rved in 1997, The alternative systems required more water per irrigation fo r uniform application, resulting in higher soil water content in the organi c systems throughout 1998, Evapotranspiration was higher in the conventiona l systems in both years relative to other systems. Tomato yields did not di ffer among systems in either year. Fruit quality was highest in the convent ional 4-yr system.