Dry Bean Response to Nitrogen Fertilizer
April 18, 2005
1. Determine the optimum level of nitrogen fertilizer for dry bean yield and quality.
2. Compare dry bean performance with N fertilizer to that with inoculant.
3. Evaluate the effect of split N application.
4. Study the response to N management strategies in contrasting plant types.
5. Disseminate the results to appropriate user groups.
Benefits to North Dakota and Minnesota dry bean growers
The results of this project will assist growers, crop consultants, extension personnel and researchers in determining the most effective and economically viable strategy for managing N in dry bean to achieve high yields and quality.
Description of research
Field trials were conducted at the NDSU Carrington and North Central (Minot) Research Extension Centers to evaluate nitrogen (N) management of dry bean. Seven levels of N were evaluated without inoculation with Rhizobium, as well as a comparison with and without inoculation at the lower N levels and an evaluation of the response to split applications of N (pre-plant and side-dressed prior to flowering). Soil test data (0-24") indicated 15 lbs NO3--N in Carrington and 51 lbs in Minot. Urea (Carrington) or ammonium nitrate (Minot) was broadcast to the desired levels of total N and incorporated in the 10" x 22-25" plots prior to planting on 14 June in Carrington and 28 May in Minot. Plots consisted of four 30" rows and were arranged in a randomized complete block design with 4 replicates. Cultivar "Maverick" (pinto) was evaluated at both sites. At Carrington, cultivar "Vista" (navy) was also included and a split-plot arrangement was used with cultivar as the main plot factor and N treatment as the subplot factor. Weeds were controlled with herbicide, cultivation, and hand rouging. Significant insect and disease pressure was not observed at either site. Slight hail damage occurred on 6 June and 25 August in Minot and a light frost on 20 August at both sites.
Outcomes and findings
The 2004 growing season was exceptionally cool. Maverick reached physiological maturity at both sites, while Vista was killed by frost before achieving maximum yield. However, no significant cultivar x N treatment interactions were observed in Carrington and the navy bean data is included as recorded.
In Carrington, the yield of Maverick was superior to that of Vista (Table 1). The failure of Vista to reach physiological maturity before frost was undoubtedly a key factor in this difference. Across cultivars, yield peaked at 100 lbs total N / acre and all treatments with less than 75 lbs total N / acre yielded significantly less than the 100-lb treatment. Across cultivars and inoculation treatments, incremental yield increases were observed as total N increased from 15 to 50 to 75 lbs / acre (Table 2). Inoculation resulted in slight yield decreases at all 3 N levels tested. Side-dressing N treatments showed no advantage over applying 100 lbs pre-plant.
In Minot, no statistically significant (P < 0.05) yield differences were observed (Table 3). However, 75 lbs total N / acre or higher tended to increase yield over the lowest N treatments. Yield was numerically highest with 200 lbs PPI and the split application. Inoculation resulted in a slight yield increase at each N level tested.
The 2004 results of this trial are inconclusive. The current recommendation of 100 lbs total N / acre for a 2000-lb yield goal seems appropriate. However, yields at both sites may have been reduced by environmental stresses (cool weather, frost, hail), which may have prevented better expression of treatments. The consistent slight response to inoculation at Minot is interesting, since this field did not have a previous history of dry bean production, whereas the Carrington site did. The lack of cultivar x N treatment interaction at Carrington is encouraging, in that it suggests that the results of this research may apply to a broader range of cultivars and market classes.