Alfalfa nodulation and growth on soil from a raw septage land application site

Abstract

Sewage disposal is a serious problem for many communities. Land application is the most economical disposal method, but concerns exist about the effects of sewage on public health, water quality, and agricultural crops. This study was done to determine if long‐term, raw septage application to alfalfa cropland affected alfalfa nodulation and growth. Seedlings grown for 6 weeks in the greenhouse were 96.2% nodulated in the control and 100% in all other treatments on the soil receiving septage, indicating that a large native population of rhizobia existed in that soil even though its pH was 5.7. Only 3.8 and 1.4% of the plants grown on the soil not receiving septage were nodulated in the uninoculated control and in the inoculated treatment plus 55 kg N^‐1 ha respectively. Simple inoculation and inoculation plus lime pelleting of seed increased nodulation to 68.5 and 62.4%, respectively, on the nonseptage‐soil (pH 5.4). Plant shoot and root weights were consistently higher on the soil with septage, compared to the other soil. Seed inoculation on the septage‐treated soil improved plant shoot and root weights over the uninoculated control. Nitrogen fertilizer increased root weights over the inoculated treatment on the septage‐soil. None of the treatments improved shoot or root growth on the nonseptage‐soil. Septage soil application improved nodulation and growth of alfalfa, possibly by providing nutrients, increasing humus, raising the soil pH, adsorbing herbicide residues, and providing a substrate for a native rhizobia population.

Key words:

• Domestic sewage
• Lime‐pelleted seed
• Medicago sativa
• Pollution
• Rhizobium meliloti