Does Soil Nutrient Management with Nitrogen Fertilizer Increase Protein Content in Leguminous Plants

Abstract

Dry edible beans (Phaseolus vulgaris) are leguminous plants and are an excellent source of dietary proteins. Great Northern (GN) beans are a market class of dry edible beans and a major agricultural commodity in Nebraska. Soil nutrient management with nitrogen (N) fertilizer can enhance bean production by increasing N uptake, potentially improving protein quantity, and resulting in a potential economic benefit to bean farmers. Thus, this experiment aims to evaluate and optimize the effects of N treatment on yield, total protein, and soluble protein in GN beans. Seven treatments were tested, consisting of two controls and 5 treatments of urea at different rates. This field trial used a randomized complete block design (RCBD) structure, with four replications per treatment. GN beans were planted in May 2021, fertilized in June, and harvested in September 2021. Yield was calculated, total protein content was measured via the Dumas method, and soluble protein content was analyzed by Lowry’s protein estimation method. Bean yield linearly increased with fertilizer N rate. Bean yield ranged from 3260 lbs/ac at 0 lbs N/ac to 3710 lbs/ac at 125 lbs N/ac. Results also showed that both total and soluble protein content in GN beans linearly increased with applied N rate. The urea treatment at a rate of 100 and 125 lbs /ac increased the total protein content by 1.0 and 2.9%, respectively. Soluble protein content increased by 1.2 and 1.8% when urea was applied at rates of 100 and 125 lbs/ac, respectively. As the demand for plant-based protein continues to grow, it brings a large market for legume proteins that can be optimized with N management. The use of N management to enhance the bean quality by increasing total and soluble protein will add more economic value to the GN beans and benefit the bean growers.