Effects of Rhizobia Inoculation, Phosphorus and Potassium on Chlorophyll Concentration of Soybean Grown under Maize Intercropping System

Aims: The study was conducted to assess the effects of Rhizobia inoculation, supplemented with phosphorus (P) and potassium (K) under intercropping system on soybean chlorophyll content.

Study Design: The design of the experiment was split-split plot with three factors factorial and replicated thrice.

Place and Duration of Study: The experiment was carried out for two consecutive years 2015 and 2016 at the Tanzania Coffee Research Institute farm in Northern Tanzania.

Methodology: Two inoculation treatments, four intercropping systems and seven fertilizer levels (kg ha-1): Control, 20, 40 K, 26, 52 P, 26 P + 20 K and 52 P + 40 K. Chlorophyll concentrations were extracted using dimethyl sulphoxide (DMSO). Spectrophotometer was used to read the absorbance values at 645 nm (Chlorophyll b) and 663 nm (Chlorophyll a).

Results: Rhizobia inoculation significantly (p=.05) increased total soybean leaf chlorophyll content from 4.25±0.30 to 5.32±0.34 and 7.20±0.27 to 7.88±0.29 in 2015 and 2016 cropping seasons respectively. P and K fertilization also significantly (p=.05) increased soybean total leaf chlorophyll content from 1.69±0.23 to 7.17±0.51 and 4.62±0.33 to 9.87±0.48 in 2015 and 2016 cropping seasons respectively. The combined fertilizers had higher mean values of chlorophyll concentration over all other treatments in both 2015 and 2016 cropping seasons.

Conclusion: Therefore, for improved chlorophyll concentration, P and K should be applied in combination at low rate of 20 K + 26 P (kg ha-1). Doubling of these fertilizers may be costly and will not significantly change the leaf chlorophyll content.