Can biochar and chitin as organic soil amendments be alternatives to manures for rocket (Eruca sativa Mill.) growth?

Organic amendments are sustainable, and relatively cheap materials derived from plants and animals that are supplemented into the soil for the restoration of the soil's physical and chemical properties, and provide the plants' nutrients before seeding, increasing its productivity. The addition of organic amendments to agricultural soil is recommended to improve soil functions and plant growth. The objective of this study was to evaluate the impact of different organic soil amendments (biochar chitin, horse, sheep manure) on the growth of rocket plants (Eruca sativa Mill.) and answer if biochar and chitin can be alternatives to manures. This study was conducted in pots, under various combinations of organic amendments, using a typic xerofluvent agricultural soil, in the spring of 2016. To experiment, four organic amendments (biochar, chitin from shrimp shells, horse and sheep manure) were employed to amend the soil, in a completely randomized design, analyzing the impact of 4% and 8% biochar, 2% and 3% chitin, as well as 2% and 5% horse or sheep manure on the growth of rocket (Eruca sativa Mill.). According to the findings, the best growth rate of the rocket was found in the sheep manure amendment at 2% rate, followed by the 5% rate, in the horse manure amendments at 2% and 5% rates, in the biochar amendment at 4% rate, and in chitin at 3% and 2% rates consecutively. Positive effects of organic amendments on plant growth were more evident under the amendments related to sheep manure at a 2% rate.