CROP PRODUCTION AND NITROGEN LEACHING RESULTING FROM BIOWASTE AND ONION COMPOST AMENDED SAND

Compost application to agricultural land needs to ensure sustainable development.
Hence it is important to determine the fertilizer value and soil conditioning ability of composts,
and further to assess the risk of adverse environmental effects, such as excessive nitrate leaching.
A lysimeter study was undertaken on poor quality sand to determine the effects of biowaste and
onion compost application on forage maize production and nitrate leaching, under high drainage
rate conditions. The two composts were applied at rates of 100, 250, 400 and 600 kg total N ha-1.
Rates of mineral fertilizer N were used as reference treatments. Under the conditions of the
study, mineral fertilizer had a poor effect on crop production, while resulted in excessive N
leaching losses. The onion compost application (C: N ratio = 10) at rates > 250 kg total N ha-1
significantly increased crop yield compared to the control treatment, and the mineral fertilizer
treatments. The biowaste compost (C: N ratio = 21) did not enhance crop yield. Both composts
did not increase nitrogen leaching losses compared to the control treatment, and they were
advantageous over mineral fertilizers from a water quality perspective.