ORGANIC SOIL AMENDMENTS: IMPLICATIONS ON FRESH TOMATO (SOLANUM LYCOPESICUM) YIELD, WEED DENSITY AND BIOMASS
J. Chipomho1*, L. Mtali-Chafadza1, B. P. Masuka1, M. Murwira1 I. Chabata2, C. Chipomho3 and B. Msindo3.
1Marondera University of Agricultural Sciences and Technology. P.O. Box 35, Marondera, Zimbabwe.
2 University of Zimbabwe, Department of Crop Science, P. O. Box MP 176 Mt Pleasant Harare Zimbabwe.
3 Kushinga Phikelela National Farmer Training College, P. Bag 3705, Marondera, Zimbabwe.
*Corresponding Author email: jusychipomho@gmail.com
ABSTRACT
Low soil fertility and weed pressure are among the major challenges affecting field and horticultural crops. Field experiments were conducted at Marondera University of Agricultural Sciences and Technology in Zimbabwe during 2015-16 and 2016-17 to evaluate the effect of organic manure sources on tomato yield, weed density and biomass. Manure from cattle, goats and indigenous chickens were tested with and or without mineral (NPK) fertilizer. A total of eight treatments arranged in randomised complete block design replicated thrice were used. Results showed an increase in tomato yields by 36.94%, and 37.07% in treatments combining mineral fertilizer with cattle or goat manure compared to sole mineral fertilizer. Concomitantly applied organic soil amendments (OSAs) did not only benefit the tomato crop but resulted in higher weed density from sole and mineral fertilizer combined treatments of goat and cattle manure. Likewise above ground dry weed biomass showed an increase by 65.36 – 95.41% higher in sole and mineral fertilizer combined treatments of goat and cattle manure compared to sole mineral fertilizer treatments. Lower weed biomass was recorded from sole and mineral fertilizer combined treatment of chicken manure which was not significantly different from the standard mineral fertilizer application. A positive correlation (r= 0.79, P≤0.02) was recorded between weed biomass and fresh tomato yield meaning that applied OSAs did not only cause yield incremental benefits to tomato crop but weeds benefited as well. This implies that weed management should be vigilant in fields with improved fertility levels due to potential weeds being introduced from animal manure and increased weed growth that may result in weed crop competition. Results further suggested that chicken manure have potential of reducing weed biomass without affecting tomato yields in low nutrient soils when used in combinations with mineral fertilizers. It is therefore be concluded that OSAs has great potential in rehabilitating depleted soils and should be well cured before they are applied to field or horticultural crops in order to reduce weed prevalence.
Key words: Depleted soils, mineral fertilizers, organic soil amendments, small-scale farmers.
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