Effects of accessions and fertilizer levels on agronomic characteristics, forage biomass yield and nutritive value of lablab (lablab purpureus L) under irrigation in dry lands of Ethiopia

The objective of the experiment was to evaluate effects of fertilizer level on lablab accessions (Lablab purpureus, (L.) Sweet) agronomic performance, forage yield and chemical composition under irrigation condition. The field study conducted in factorial arrangement of randomized complete block design (RCBD) using two factors (three lablab accessions and four fertilizer levels) with three replications. The three lablab accessions were accession 147, 11640 and Tulu combined with four fertilizer levels of NPS (0, 50, 100 and 150 kg/ha). All levels of nitrogen, phosphorus and sulfur (NPS) were applied at time of planting for all lablab accessions. The agronomic characteristics and forage yield data were collected at 50% flowering stage, weighed (for yield estimation), dried and then ground subsamples taken for analysis of crude protein, ash, dry matter, fiber contents, in vitro dry matter digestibility and total digestible nutrients. The collected data were subjected to general linear model for statistical analysis system (SAS) version 9.0. The result indicated that there was significant interaction (P < 0.05) effect in the fertilizer level and accession only in the length and number of leaves per plant, but not for all chemical compositions of lablab. The three accessions showed significant difference (P < 0.001) in the majority of agronomic characteristics. Also fertilizer level showed significant effect (P < 0.001) on the majority of agronomic characteristics. The lablab accessions grown in higher level of NPS fertilizer (150 and 100 kg/ha) had better agronomic performance and dry matter yield than those grown in lower fertilizer levels. Overall, significantly (P < 0.001) maximum dry matter yield (19.6 t/ha) was recorded from Tulu varieties while the lowest dry matter yield (11.21 t/ha) was from lablab accession 147. Regarding fertilizer levels, maximum dry matter yield was recorded from 150 kg fertilizer NPS application (17.03 t/ha) while the lowest (13.5 t/ha) was recorded from control treatment group. The highest CP content (21.6%) was recorded from 11640 lablab accession while the lowest (20.5%) was from Tulu lablab accession. With regard to fertilizer levels, the highest CP content was recorded from 150 kg/ha fertilizer (22.9%) while the lowest (19.4%) CP was recorded from control. Therefore, among tested lablab (Tulu and 11640) accessions with the 100 kg/ha fertilizer rate given priority in terms of their yield and chemical composition and are recommended for wider utilization under smallholder farmers condition in the farming system with similar agro-ecologies using irrigation season. Further research on the economic analysis of cultivars under different systems of production is required to increase viability of this finding