Abstract
Arbuscular mycorrhizal (AM) fungi can increase plant uptake of nutrients especially relatively immobile elements such as P, Zn and Cu and consequently, improve plant growth and yield. The study was conducted to identify native AM strains, multiply and test their effects in reduction of P fertilzer in vegetables and spices production. Rhizosphere soils and roots of two vegetables (tomato and brinjal) and two spices (chilli and onion) crops were collected from each of four AEZS, viz. AEZ-9 (RARS, Jamalpur), AEZ-11 (RARS, Jashore), AEZ-25 (ARS, Bogura) and AEZ-28 (BARI, Joydebpur) in 2013- 2014. Characterization and identification of arbuscular mycorrhizal strains was studied in the microbiology laboratory of Bangladesh Agricultural Research Institute (BARI). Eleven AM strains were identified in tomato: Glomus geosporum, G. mosseae, G. fasciculatum, G. spp., Acaulospora dilatata, A. bireticulata, A. mellea, A. morrowiae, Entrophospora infrequens, Sclerocystis coremioides and Gigaspora margarita. Nine each were identified from other three crops. G. spp. and Acaulospora bireticulata were absent in brinjal and chilli. Acaulospora dilatata and A. mellea were absent in onion. The collected mycorrhizal strains were maintained with trap crop sorghum under net house condition at BARI, Joydebpur in 2013-2014 onwards. Rhizosphere soils containing AM strains (identified from four crops) were used for sorghum culture in separate earthen pots, mixing with sandy clay loam soil in 1:1 ratio. Higher % root colonization and number of spore in trap crop than corresponding values in original crops' rhizosphere indicated that sorghum was an effective trap crop. The best performing AM strain was selected from pot experiments at greenhouse of BARI. The sandy clay loam soil was used as the potting media. Eleven AM strains collected from tomato fields of four AEZs and maintained in sorghum trap crop were tested with tomato. Similarly, nine each AM strains each from brinjal, chilli and onion were tested with corresponding crops in three separate pot experiments. Randomized Complete Block Design (RCBD) was followed with four replications. Dry matter yield (both root and shoot), some vegetative parameter, % root colonization and number of spores were observed. Considering these parameters, Glomus mossene was selected as best performing one for all four crops. Finally the efficiency of the selected mycorrhiza, Glomus mosseae, was tested under field condition during 2015-2016 and 2016- 2017. Factorial RCBD was followed for field experiments with eight treatments and four replications. The treatments were: T1: 0%P - AM, T2: 50%P - AM, T3: 75%P - AM, T4: 100%P - AM, T5: 0%P + AM, T6: 50%P + AM, T7: 75%P + AM and Ts: 100%P + AM. 100% P for tomato, brinjal, chilli and onion was equal to 38, 30, 48 and 40 kg ha-1 P, respectively. Tomato (BARI Tomato-14), brinjal (BARI Begun-8), chilli (BARI Morich-1) and onion (BARI Piaz-1) were used as test crops. Selected soil-based AM inoculum (Glomus mosseae) those preserved in sorghum culture were used in seedbed of respective crops. Many morphological parameters and yield attributes were found as highest from 75% P + AM inoculation in comparison to 100% P - AM. The highest crop yield of tomato, brinjal and chilli was found from 75% P+AM, which was statistically similar to 100% P-AM. Thus, it could be concluded that there is a possibility of saving 25% P in these three crops in AEZ 28 of Bangladesh. Benefit cost ratio (BCR) revealed that the highest BCR was found for tomato, chilli and onion with the treatment receiving 75%P along with full doses of chemical fertilizers (NKSZnB) in combination with AM, but in case of brinjal the highest BCR was noted from the treatment having full doses of all chemical fertilizers plus AM. From the study, it can be concluded that mycorrhizal inoculation (Glomus mosseae) could save 25% P in vegetables and spices cultivation.