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

Authors: DUAN, YINGHUA - Chinese Academy Of Agricultural Sciences; Gao, Suduan; HANSON, BRAD - University Of California, Davis

Submitted to: Soil Use and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2021
Publication Date: 2/1/2022
Citation: Duan, Y., Gao, S., Hanson, B.D. 2022. Effects of biochar and fertilizer sources on nitrogen uptake by chilli pepper plants under Mediterranean climate. Soil Use and Management. 38(1):714-728. https://doi.org/10.1111/sum.12759.
DOI: https://doi.org/10.1111/sum.12759

Interpretive Summary: Chili pepper is an important cash crop for farmers in many countries, but little information is available on the crop N requirement that can guide effective nitrogen (N) management and minimize negative environmental impact. This study determined N uptake by serrano chili pepper plants (Capsicum annuum) for two consecutive years and evaluated the effects of soil amendment with biochar or incorporation of organic-N fertilizer under a Mediterranean climate. The results suggest that pepper fruit yield were the highest from combination of inorganic and organic N fertilizers at 50:50 during the first year although no differences in the second year. Biochar was not conclusive to improve yield, but significantly increased soil organic carbon, a key indicator of soil productivity. The research concludes that serrano chili pepper plants require 4.6 - 6.1 kg N for production of one tonne of fresh pepper fruits that can guide N fertilizer applications and effective N management should focus on improving N productivity in soil for sustainable crop production.

Technical Abstract: There is little information on nitrogen (N) uptake data on chili peppers (Genus Capsicum) that can assist in development of effective N management strategies. This study determined N uptake by serrano chili pepper plants (Capsicum annuum) for two years and evaluated the effects of soil amendment with biochar or incorporation of organic-N (org-N) fertilizer under a Mediterranean climate. A field experiment was conducted using microplots from 2016 - 2017 in the San Joaquin Valley, California, USA. Treatments included biochar amendment rates [0 (control), 10, 30, and 50 tonne (t) ha-1] of a coconut shell biochar (CoolTerra®) with 100% inorganic (synthetic) fertilizer, and incorporation of org-N fertilizer (True Organic® 4-4-2) at 50%, 75%, and 100% of total available N supply (165 kg N ha-1). Pepper yield, vegetative biomass, N uptake, ammonia (NH3) volatilization, and changes in soil organic carbon (SOC), nitrate, and total N content (STN) were determined. Pepper yield were the highest from the 50% org-N or lowest from the 50 t ha-1 biochar treatment during the first year but showed no differences among the organic treatments during the second year except lower value from the control. The 100% org-N showed reduction in NH3 volatilization first year but not second year. Nitrate downward movement from all treatments were observed in the second year suggesting effect of irrigation and/or time on leaching. This research concludes that serrano chili pepper requires 4.6 - 6.1 kg N for production of one t of fresh pepper fruits. The highest N productivity (lowest N sequestered by whole plant per unit fruit yield production) corresponded to the highest yield from the 50% org-N treatment first year. Incorporation of biochar at 10 t ha-1 maintained SOC after two years of application, and combination of inorganic and org-N fertilizers offers the advantage to improve soil N productivity under the Mediterranean climate.