Assessing nitrogen supply potential and influence on growth of lettuce and 'Amaranthus' of different aged composts

This study assessed the potential of different composts at different maturity stages to supply N and their effect on the vegetative growth of lettuce and 'Amaranthus'. Five composts aged 1, 3, 6, 9, and 12 months, were mixed with soil @ 5%, 10% and 15% then seeded with lettuce and 'Amaranthus'. Results showed that 1, 3 and 6 month aged composts had a negative effect on plant height of lettuce and 'Amaranthus' as 1–15.78% and 4.78 to 29.45% decrease in plant height over control was recorded respectively. On the other hand 9 and 12 month aged composts had a significant positive effect on plant height of lettuce and 'Amaranthus' where 43.48% and 34.8% increase over control was recorded with the application of 15% of 12 month aged compost respectively. A similar effect was observed on fresh biomass of both lettuce and 'Amaranthus' where a 386% and 59.43% increase over control was recorded with the application of 15% of 12 month aged compost respectively. One and three month aged composts revealed a negative effect on N absorption by lettuce whereas 1, 3, 6 and 9 month aged composts had a negative effect on N absorption by 'Amaranthus'. 30.39% and 21.48% increases over control in N absorption by lettuce and 'Amaranthus' respectively were recorded with the application of 15% of 12 month aged compost.