Influence of Dairy Cattle Slurry Solid Fraction Compost Combined with Mineral Nitrogen Fertilizer on the Growth of Greenhouse Lettuce

Winter lettuce response to the application of composts from the solid fraction of dairy cattle slurry was assessed in combination with mineral nitrogen (N) fertilizer throughout a randomized block experiment under greenhouse conditions. Lettuce yield did not increase with mineral N fertilizer, possibly because the lettuce was preceded by a heavily fertilized tomato crop, and the amount of mineral N (114 kg ha^-1) in the soil at the beginning of the experience was greater than the amount of N (64-89 kg ha^-1) accumulated in the lettuce shoots of all of the treatments. In contrast, lettuce yield and N uptake increased with compost application, suggesting other benefits in addition to N availability resulting from its use as a soil amendment. Therefore, dairy cattle slurry solid fraction mature compost can be recommended for vegetable production, and mineral N recommendation is suggested to pursue previous soil mineral N analysis.