Soil Amendments Enhanced Summer Squash Yield, Fruit Composition, Quality, and Soil Enzymes Activity

Summer squash, Cucurbita pepo was field grown under fourteen soil treatments: sewage sludge (SS);horse manure (HM);chicken manure (CM);vermicompost;inorganic fertilizer (Inorg);commercial organic fertilizer (Org);and no-mulch (NM) control treatment. Soil treatments were also mixed with biochar to make a total of 14 treatments to assess the impact on 1) squash fruit yield and quality, 2) fruit vitamin C, total phenols, and soluble sugars content, and 3) soil microbial activity expressed as urease and invertase secretions. Results revealed that SS treatments increased squash yield and fruit number by 114% and 116%, respectively compared to NM control treatment. Fruits of plants grown in Inorg mixed with biochar (InorgBio) increased fruits’ vitamin C, total phenols, and soluble sugars by 73%, 52%, and 7%, respectively compared to Inorg with no-biochar treatment. However, biochar was not consistent in increasing soil urease and invertase activities. The use of animal manure is an affordable way to reduce dependence on mineral fertilizers. Results revealed that the addition of biochar to Org fertilizer increased squash fruit weight and numbers of fruits compared to Org not treated with biochar. No single amendment increased all fruit composition and soil urease and invertase activities.

UV/Vis Characterization and Fate of Organic Amendment Fractions in a Dune Soil in Dakar, Senegal

The application of organic amendments on soils poor in organic matter(OM) can improve long-term soil fertility, but may also enhance the mineralization of native soil organic matter. Three organic amendments, compost, sewage sludge and horse manure, used by urban market gardeners in Dakar, Senegal were analyzed for their OM maturity. Their fate was evaluated in a 45-d agronomic trial in a sandy Arenosol with lettuce. In each case, water-extractable organic matter(WEOM) and humic-like substances(HLS)were isolated from raw amendments and amended soils, and characterized using ultraviolet-visible(UV/Vis) spectroscopy. Results highlighted the general more aromatic character of HLS and WEOM fractions extracted from compost compared to the other two amendments. When applied to soils, however, these differences were not clearly observed. The aromaticity and humification degree of the labile fraction(WEOM) increased with depth in the first 30 cm for all amendments. This indicated the high lixiviation rates that fresh OM underwent in the studied sandy soil. Finally, a statistical analysis of the results was able to discriminate between surface and deeper horizons and between amended- and non-amended soil samples. Spectroscopic indices showed indeed strong increase/decrease with depth linked with the mineralization/humification processes that the fresh OM from amendments underwent during the 45 d of the agronomic trial. This study highlights the potential of spectroscopic techniques to study agricultural amendment organic matter fractions and their fate in soils.