Grass–Legume Forage Systems Effect on Phosphorus Removal from a Grassland Historically Irrigated with Reclaimed Wastewater

Everald Mclennon, Juan K. Q. Solomon and Jason Davison
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Everald Mclennon: Department of Natural Resources & Environmental Science, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557, USA
Juan K. Q. Solomon: Department of Agriculture, Veterinary & Rangeland Sciences, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557, USA
Jason Davison: Extension, College of Agriculture, Biotechnology & Natural Resources, University of Nevada Cooperative Extension, 111 Sheckler Road, Fallon, NV 89406, USA

Sustainability, 2020, vol. 12, issue 6, 1-18

Abstract: The utilization of reclaimed wastewater is a suitable and sustainable approach to agriculture production in water-scarce regions. However, even though the wastewater is treated to reduce nutrient concentration such as phosphorus, the 10,600 to 14,006 m 3 of water applied ha −1 year −1 on grass and alfalfa hay crops in Nevada can lead to soil phosphorus buildup over an extended period. This study evaluated the effectiveness of forage systems (FS) of monoculture grass, monoculture legume, and their mixtures on herbage accumulation, tissue phosphorus concentration, and quantity of phosphorus removed from a grassland under wastewater irrigation. The study was carried out at the Main Station Field laboratory in Reno, Nevada, USA. A total of 23 FS using tall fescue ( Schedonorus arundinaceus (Schreb.) Dumort), alfalfa ( Medicago sativa L.), red clover ( Trifolium pratense L.) and white clover ( Trifolium repens L .) in monocultures or grass–legume mixtures (25:75, 50:50, and 75:25) based on seeding rate were used. The response variables were herbage accumulation (HA), tissue phosphorus concentration, and phosphorus removal. Forage systems means were considered different P ≤ 0.05. Herbage accumulation, tissue phosphorus concentration, and phosphorus removal differed among FS and year. Herbage accumulation was similar for the grass monocultures (10.5 Mg ha −1 ; SE = 1.1) and the majority of the grass–legume mixtures (9.0 Mg ha −1 ; SE = 1.1) but both systems had greater HA than legumes monoculture (4.3 Mg ha −1 ; SE = 1.1). The legume monocultures of alfalfa and white clover had the greatest phosphorus concentrations (10.9 g kg −1 dry matter; SE = 0.44) among all FS. Total phosphorus removed was least among legume monocultures (34.0 kg P ha −1 ; SE = 6.2) in this study and generally similar for grass monocultures (67.4 kg P ha −1 ; SE = 6.2) and grass–legume mixtures of 75:25 (61.7 kg P ha −1 ; SE = 6.2). Based on the response variables, agronomic, and environmental considerations a grass–legume mixture that includes 75:25 or even a 50:50 seeding rate ratio will be suitable options for phosphorus removal from phosphorus enriched grasslands in semiarid ecosystems that utilized wastewater for irrigation.

Keywords: alfalfa; amelioration; environmental protection; herbage accumulation; phosphorus removal; phytoremediation; red clover; tall fescue; tissue phosphorus concentration; white clover (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2020
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