Effect of seed scarification, rhizobium inoculation and phosphorus fertilization on root development of barseem and soil composition

Barseem (Trifolium alexandrinum L.) is a common rabi grown legume fodder crop that fits well in the farming system at the irrigated lands in Pakistan. Variation in per acre productivity could be attributed to varietals differences and variation in agronomic practices. The current experiment was designed to assess the effect of seed scarification, phosphorus fertilization and rhizobium inoculation on post-harvest soil nitrogen and root development of barseem. The five treatments viz. (A) control, (B) scarified seeds, (C) P-fertilization, (D) Rhizobium inoculation and (E) Rhizobium inoculation + P-fertilization were applied in a Complete Randomized Block Design using three replicates per treatment. Plant height remained the same during the first three and fifth cuts, however, significant (P less than 0.05) differences were observed during the fourth cut of barseem. Treatment C and E yielded the maximum height followed by treatment D, A and B. Me an plant height during the successive cuts were 30.1, 47.1, 52.1, 56.7, and 54.3 cm, respectively. Pre-trial soil nitrogen content was 0.12%, which apparently did not change in response to any treatment. Mean soil-N after the last cutting of barseem was 0.068% across the five treatments. Post-harvest phosphorus content in the soil increased in plots, which were fertilized with phosphorus. The low mean phosphorus content in the fodder (0.21 %) may be attributed to the low pre-trial soil phosphorus concentration (71 mg per kg). Phosphorus application and rhizobium inoculation in isolation or in combination tended to enhance root development i.e., root length, number of nodules and root hairs per plant in the present study but due to large variation between the replicates with in the treatment the effect on root development was statistically insignificant. The average number of nodules per plant (138) in the present study was markedly higher than the maximum number (71) reported in literature. Phosphorus fertilization in isolation or in combination with rhizobium inoculation enhanced phosphorus reserves of the soil and strengthened the root vigour to support more yielding cuts.