Common bean is an important crop with potential to curb malnutrition in poor Sub-Saharan African populations. Yields of common bean (Phaseolus vulgaris L.) are, however poor, limited by low soil phosphorus (P), nitrogen (N) and poor biological N2-fixation. On-farm experiments were carried out to study the effect of N, P and rhizobia inoculation on common bean yield and yield components during the 2014/2015 and 2015/2016 cropping seasons in Eastern Zimbabwe. Experiments were conducted on five farmersβ fields located in two
agroecologies; three fields were considered to be degraded with soil organic carbon (SOC)<4 g kgβ1 and available P < 6 mg kgβ1, while the two nonβdegraded sites had SOC > 7 g kgβ1 and available P > 15 mg kgβ1. Two common bean varieties (Gloria and NUA45) were tested in a split-plot arranged in randomized complete block design. The main plot factor was the combination of N (0 and 40 kg haβ1) and P (0 and 20 kg haβ1), and the sub-plot factors were variety (Gloria and NUA 45) and inoculation with Rhizobium tropici strain CIAT899 (+/β inoculum). At planting, both N and P were applied at 20 kg haβ1, with an additional 20 kg haβ1 N top dressing applied at flowering. Analysis of variance indicated common bean did not
respond to rhizobia inoculation (P > 0.05) whilst P significantly increased the number of nodules and active nodules per plant (P < 0.001), and grain yield. Application of 40 kg haβ1 N significantly increased the number of pods per plant, number of seeds per pod, and grain yields. A significant NP interaction was only observed on grain yield for non-degraded soils. Co-application of N and P in non-degraded sites increased grain yields from 0.27 to 1.48 Mg haβ1 during the first season and from 0.37 to 2.09 Mg haβ1during the second season. On degraded sites, NP application resulted in uninspiring grain yield gains of 0.09 to 0.19 Mg haβ1 during the first season, and from 0.16 to 0.28 Mg haβ1 in the second season. In general, effects of N or P were not significantly different, suggesting that farmers could invest in either of these nutrients for increased common bean grain yields. Strategically, P investments would be more logical as residual P effects to rotational cereals improve overall cropping system performance. The response of common bean to inoculation in Zimbabwe still needs to be widely investigated for these and other varieties.
Description
Reference
Agriculture, Ecosystems and Environment, 266, 167β173
Link
Year
2018