5.1.16
THE USE OF SOIL SOLARIZATION TO CONTROL WEEDS AND PLANT DISEASES, AND INTEGRATION OF CHICKEN LITTER AMENDMENT, FOR TOMATO PRODUCTION IN TANZANIA

VA KHAN2, D MUSHOBOZY1 and C STEVENS2

1Department of Crop Science, Sokoine University of Agriculture, Morogoro Tanzania; 2George Washington Carver Agricultural Experiment Station, Tuskegee University, Tuskegee, AL 36088, USA

Background and objectives
Soil solarization is a plasticulture technology that involves the use of a hydrothermic process where clear plastic mulch is used to trap solar energy to sterilize the soil to control soilborne pests such as weeds, nematodes and soilborne pathogens, and to maintain a sustainable system that is involved in producing fertilizer [2]. Recently, soil solarization has been reported to control foliage diseases [2]. The main objective of this study was to determine its efficacy to control weeds and soilborne pathogens, and to determine the effect of chicken litter amendment applied in combination with soil solarization to improve the yield of tomatoes.

Methods and materials
All experiments were conducted in field plots at Sokoine University of Agriculture, Morogoro, Tanzania. Two experiments were conducted from 1995-96 on Oxisol red main clay loam soil using single-layer 48 m-thick clear plastic sheets (Polyon Barkai Kibbutz Barkai, Israel). The following rates of composted chicken litter (CCL) were incorporated in the soil before solarization and in the control: 1, 3, 5 and 8 MT/ha. In the second trial (1996), the plastic film was re-used from the previous trial in 1995. Avissar et al. [1] showed that re-using clear plastic film ensured better results, and this approach is suitable for farmers under the prevailing economic conditions in Tanzania.

Results and conclusions
This study was initiated in 1995 as a transfer of technology research project to investigate the possible use of soil solarization under Tanzanian climatic conditions. The average maximum temperature of the air and solarized soil at 5 and 10 cm depths and 5 cm depth of non-solarized soil were 29, 43, 36 and 29C, respectively. In the first solarization trial (1996), 98% control occurred of 16 species of weeds, with purple nutsedge (Cyperus rotundus) being the most dominant weed. Root knot gall damage was not as severe on tomato plant roots grown in solarized soil compared to non-solarized soil. The effect of applied CCL in combination with soil solarization was evaluated on tomato yield. The best solarized treatment was 3 M/ha CCL with soil solarization, where the total yield resulted in 19.3 MT/ha of tomatoes compared to 9.5 MT/ha in the non-solarized soil without CCL. Results from the second solarization trial (1997) showed that soil solarization was not effective in controlling Didymella stem canker on tomatoes. However, there was a 50% reduction of the foliage disease caused by the fungus. Soil solarization in this location appeared to work very well and could possibly replace the current slash and burn method.

References
1. Avissar R, Naot 0, Maher Y, Katan J, 1986. Soil Sci. J. 50, 205.
2. Katan J, DeVay JE, 1991. In Katan, DeVay, eds, Soil Solarization. Boca Raton, FL, pp. 23-36.