Asian Journal of Soil Science and Plant Nutrition

Aims: Recently freshwater lake sapropels have attracted increasing attention due to their use in agriculture and environmental engineering. To study the effect of unprocessed sapropel on soil properties and tomato (Licopersicon esculentum Mill.) yield   we conducted a microplot open field experiment in the south of West Siberia (Russia, Asian part).

Study Design: Experimental sites were located NL 54.96-55.01, EL 82.38-83.30 on agricultural loamy soils. Sapropel was added at the rate of 450 kg C_org ha^-1 and 40.5 kg N ha^-1 once at the start of the experiment after transplanting tomato seedlings into the open field. Both control (no sapropel) and sapropel-amended soil received mineral fertilizers at the rate of 30 kg N, 60 kg P and 75 kg K per hectare. Experiment was performed in factorial design, and the order of experimental units in each sites was randomized.

Place and Duration of Study: Laboratory of Agrochemistry, Institute of Soil Science and Agrochemistry, Novosibirsk, Russia, between June and September 2013.

Methodology: Major soil chemical and microbiological properties were determined at the end of the experiment. Mature tomato fruits were collected during the growing period, and their nutritional qualities determined. The data were analyzed by ANOVA and PCA.

Results: Sapropel was not found to influence tomato fruit yield that overall averaged 2.2 kg/plant, or 88,000 kg ha^-1, but was shown to increase lycopene content in fruits by 80% (from 19 up to 34 mg/kg), thus improving fruit quality. Sapropel had no effect on soil chemical properties, but increased soil microbial biomass nitrogen and its contribution into soil organic matter. Thus soil microbiological properties, pertaining to organic matter mineralization and nitrogen immobilization, were shown to be more responsive to sapropel addition than soil chemical properties.

Conclusion: To justify use of freshwater lake sapropel as a fertilizer agronomically, economically and ecologically one should take into consideration many factors, ranging from soil to interсultivar properties variation and temporal aspects such as after-effect.