Effects of biochar and fertilizer sources on nitrogen uptake by chilli pepper plants under Mediterranean climate

This study determined N uptake by serrano chilli pepper for two years and evaluated the effects of biochar amendment or organic N (org-N) fertilizer on N use under a Mediterranean climate. A field experiment was conducted using microplots from 2016 to 2017 in California, USA. Treatments included biochar amendment rates 0 (control), 10, 30 and 50 tons (t) ha^?1] biochar, all with 100% inorganic N fertilizer (165 kg N ha^?1), and org-N fertilizer applications at 50%, 75% and 100% of the total available N supply. Pepper yield, vegetative biomass, N uptake, ammonia (NH₃) volatilization and changes in soil organic carbon (SOC), and nitrate were determined. Pepper yield was highest in the 50% org-N and lowest in the 50 t ha^?1 biochar treatment during the first year. There were no differences in fruit yield among the organic treatments during the second year, and all were higher than that from the control. The 100% org-N treatment had less NH₃ volatilization than all other treatments during the first year. The two-year results showed that chilli pepper plants sequestered 4.6?6.1 kg N to produce one ton fresh pepper fruits. During the first year, the 50% org-N treatment resulted in the highest N productivity or yield with lowest projected N fertilizer application requirements as compared to other treatments although there were no differences among all treatments in the second year. Thus, a combination of inorganic and org-N fertilizers can be an effective strategy to improve soil N productivity in long-term management.