Pelletized sewage sludge as a fertilizer for containerized plants: Plant growth and nitrogen leaching losses

Abstract

To evaluate the effectiveness of sewage sludge pellet fertilizers (SPFs) for growing containerized greenhouse crops and their potential for nitrogen (N) leaching, three experiments were conducted where SPFs were compared to conventional water‐soluble fertilizer (WSF) and controlled‐release fertilizer (CRF). In different experiments ‘First Lady’ marigold (Tagetes erecta L.) and ‘Selenia’ New Guinea Impatiens (Impatiens sp. hybrids) (NGI) were grown in 0.5‐liter pots of soilless growth medium and plants were fertilized with 20N‐ 4.3P‐16.6K WSF, 14N‐6.2P‐11.6K CPF, or two types of SPF, 3N‐1.0P‐0.1K or 5N‐1.3P‐0.1K. CRF and SPFs were incorporated in the growth medium at planting. In each experiment, treatments received the same amount of N and volume of irrigation water. Leachate was analyzed for ammonium‐nitrogen (NH₄‐N) and nitrate‐nitrogen (NO₃‐N) at regular intervals and shoot dry weight was measured at the end of each experiment. SPFs alone as the sole source of N resulted in less N leaching compared to WSF or CRF alone but did not provide adequate N for marigold as shoot dry weight was reduced compared to WSF and CRF and foliar N deficiency symptoms developed. However, SPFs alone caused no such effects on NGI and shoot dry weight was equal to WSF and CRF with less N leaching. Growth of marigold increased and N deficiency symptoms were prevented by combining SPFs with a dilute solution of WSF, but the same treatment did not affect NGI. Combining SPFs and WSF in this manner for marigold resulted in less N leaching than SPFs alone, however with NGI more N leaching occurred, but not to the level of WSF and CRF. Results suggest that SPFs can provide adequate N for slow‐growing plants with low N uptake rates like NGI, but for fast‐growing plants with high N uptake rates, SPFs must be combined with more soluble fertilizers.

Notes

Paper No. 3143 of the Massachusetts Agricultural Experiment Station.