ORGANIC LETTUCE GROWTH AND NUTRIENT ACCUMULATION IN RESPONSE TO LIME AND HORSE MANURE COMPOST
A field experiment with organic lettuce (Lactuca sativa) was arranged as a randomized block factorial design with increasing rates of composted horse manure (0, 20 and 40 t ha-1) combined with lime (0 and 8 t ha-1) to assess compost mineralization, lettuce growth and nutrient accumulation in lettuce shoots. Commercial yield was significantly increased from 25.6 t ha-1 for the unfertilized control treatment to 35.8 t ha-1 attained with 40 t ha-1 of manure compost and 8 t ha-1 of lime. Mean yield increase with lime for the overall compost treatments was 15% whereas with 20 and 40 t ha-1 compost was 18 and 26%, respectively. Nitrogen content and N accumulation in lettuce significantly increased with the application of 40 t ha-1 compost but differences between 20 and 40 t ha-1 were not clear. Lettuce uptake of P, K, Ca, Mg and Fe was not significantly different between experimental treatments except for occasional differences found for K. Apparent organic N use efficiency was highest for 20 t ha-1 of compost when lime was applied (18.3%) and increased also with lime application for treatments with 40 t ha-1 of compost. This study shows the potential of horse manure compost combined with lime to increase organic lettuce yield and N uptake in low-fertility soils and for organic horticulture.
Brito, L.M., Pinto, R., Mourão, I., Rodrigues, R. and Coutinho, J. (2012). ORGANIC LETTUCE GROWTH AND NUTRIENT ACCUMULATION IN RESPONSE TO LIME AND HORSE MANURE COMPOST. Acta Hortic. 933, 157-163
Lactuca sativa, nitrogen mineralization, organic amendment, liming