Biochar particle size and Rhizobia strains effect on the uptake and efficiency of nitrogen in lentils

Abstract

Biochar has attained significant attention as a beneficial soil amendment amongst growers and researchers. However, the impact of particle size of biochar is yet to be investigated. Here in the present study, we studied three particle sizes (<2 mm, 2–5 mm, and >5 mm) of biochar and two rhizobia strains (Rhizobium leguminoserum (RL) and Rhizogold (RG)) for their effect on the uptake and efficiency of nitrogen (N) in lentils. The two years experiment followed a randomized complete block design with split plot arrangement replicated three times. The data revealed that grain N, straw N, N uptake, N recovery efficiency (NRE), and N agronomic efficiency (NAE) were maximum with biochar smallest size (<2 mm). However, the N physiological efficiency, number of branches and plant height decreased with reduced particle size. Furthermore, the smallest particle size showed more number of pod plant⁻¹. Biofertilizer strain (RL and RG) significantly increased the straw N but not the grain N. Both strains showed increased NRE and NAE, however, the RL demonstrated 7% more grain N than the RG. Both strains (RL and RG) demonstrated 16% and 20% increase in number of branches plant⁻¹, 62% and 48% in plant height and 2% and 5% in root length, respectively. The RL strain improved the number of branches plant⁻¹ at the lowest (<2 mm) and medium size (2–5 mm) particles size but both RL and RG strains demonstrated increased plant height under the maximum particle size. These results indicated that a mere increase in surface area with decreasing biochar particle size may not serve for enhancing biofertilizer strains performance since reducing particle size may immobilize the starter N applied. However, reducing particle size effect on N cycling into soil plant system was favorable.

Keywords:

• agronomic efficiency
• biochar
• biofertilizer
• physiological efficiency
• recovery efficiency

Acknowledgment

Authors highly acknowledge the laboratory facilities of the Soil and Environmental Sciences Department, The University of Agriculture, Peshawar, Pakistan, the National Agricultural Research Center and The University of Agriculture, Faisalabad for provision of Rhizobia strains for the study.

Disclosure statement

The authors declare no conflict of interests.