Abstract: Two different experiments were conducted in widely separated farmers field at Phulpur MLT site of On-Farm Research Division (OFRD), Mymensingh during the two consecutive rabi seasons of 1997-98 and 1998-99 to study the effectiveness of two promising strains of Rhizobium BARI and BAU along with chemical fertilizers on nodulation and yield of groundnut (var. Dhaka-1) and also to select the suitable combination of Rhizobium inoculum and NPKS fertilizers. Five treatment combinations such as Control, NPKS, PKS, Inoculum and PKS+Inoculum each replicated 4 times in randomized complete block design were included in the study. Significant differences were observed in all the parameters studied. Among the two strains of Rhizobium tested BAU strains performed better than BARI strain. Rhizobium inoculation alone or with PKS fertilizers produced significantly higher nodule number, pod number, pod weight, nut yield and stover yield compared to uninoculated ones. The highest nut and stover yield was produced by the treatment PKS+Inoculum. However, the economic evaluation of the crop suggested that the treatment Inoculum was most suitable for groundnut production.
Introduction
Nitrogen is the most deficient nutrient in Bangladesh soil limiting crop production. Urea, the most commonly used nitrogenous fertilizer in the country is becoming costly day by day and most of the farmers in Bangladesh cannot afford to buy the required quantities of the fertilizer for successful crop production.
Groundnut is one of the major oil seed legume crops in Bangladesh covering about 7% of the total area under oil crops and 9% of the total oilseed production (Anonymous, 1993). It is capable of fixing and utilizing atmospheric nitrogen in symbiotic association with Rhizobium bacteria. The benefits of inoculation on groundnut in Bangladesh has been demonstrated by Hoque (1988; 1993) . The use of appropriate Rhizobium strain for groundnut production may reduce the use of commercial nitrogenous fertilizer in one hand and increase the profitability of production on the other hand. With this view point, Bangladesh Agricultural Research Institute (BARI) and Bangladesh Agricultural University (BAU) have developed Rhizobium inoculants for different food legume crops. In the present study an effort was made to evaluate the effectiveness of both BARI and BAU strains of Rhizobium on the yield performance and economic benefit of groundnut.
Materials and Methods
Two separate experiments, one with BARI strain and the other with BAU strain of Rhizobium were conducted in two widely separated farmers fields at Phulpur MLT site of OFRD, Mymensingh during the two consecutive rabi seasons of 1997-98 and 1998-99 with Dhaka-1 groundnut variety. There were five treatments such as Control, NPKS, PKS, lnoculum and PKS + Inoculum each replicated 4 times in randomized complete block design. Before planting. Rhizobium inoculants were mixed with groundnut seeds with the addition of water in such a way that the inoculants were just adherent to the surfaces of seeds. Fertilizers were applied at the time of sowing according to the treatment as per BARC Fertilizer Recommendation Guide (1997). Seeds were sown on 15-18 January with recommended spacing of 40×15 cm. Weeding was done when necessary and fungicides were applied to control Tikka disease.
Ten randomly selected plants were uprooted from each plot at nut formation stage of crop and data on nodule number and pod number per plant were recorded. At maturity, the crop was harvested and nut and stover yields were recorded. The data were analysed statistically by means of ANOVA technique. The differences among the treatment means were evaluated by Duncan's New Multiple Range Test (DMRT) (Steel and Torrie, 1960).
Results and Discussion
Results on nodule number, pod number and pod weight are presented in Table 1; on nut yield and stover yield are presented in Table 2 and economic evaluations are presented in Table 3.
Both BARI and BAU strain of Rhizobia inoculation in presence of phosphorus, potassium and sulphur resulted significant increase in nodule number, pod number and pod weight during the two consecutive rabi seasons of 1997-98 and 1998-99 (Table 1). Rhizobium inoculation without any chemical fertilizer gave significantly higher nodule number, pod number and pod weight compared to uninoculated control. This result is in agreement with Rahman et al. (1992) who found that Dhaka-1 variety of groundnut with Rhizobium strain RAH-805 recorded 32 and 140% higher nodule number. Plant receiving NPKS and PKS fertilizers produced identical nodule number, pod number and 100 pod weight. In case of all parameters recorded BAU strain performed better than BARI strain.
Inoculated plants along with nitrogen, phosphorus, potassium and sulphur fertilization produced significantly higher nut and stover yield compared to uninoculated ones during the two consecutive rabi seasons (Table 2). Plant receiving inoculum alone gave higher nut and stover yield than control. The treatment PKS + inoculum produced the highest nut and stover yield. The yields produced by NPKS was at par with PKS.
The economic evaluation of groundnut production through Rhizobium inoculation reveals that the highest nut yield and gross margin were obtained from the treatment PKS+Inoculum but the benefit cost ratio was highest only for inoculum treatment. Bhuiyan et al. (1996) also found similar result in a trial of groundnut with rhizobial inoculant. Hence application of only inoculum was the most suitable treatment for groundnut production from economic point of view. However, the rich farmers may use the treatments PKS+Inoculum through additional investment to increase gross margin profitable.
| Table 1: | Nodulation and yield components of groundnut as affected by inoculants and NPKS fertilization |
| Figures in a column having letter (s) in common do not differ significantly but figures bearing dissimilar letter(s) differ significantly at 1%level of probability | |
| Table 2: | Pod and stover yield of groundnut as affected by inoculant and NPKS fertilization |
| Figures in a column having letter (s) in common do not differ significantly but figures bearing dissimilar letter(s) differ significantly at 1%level of probability | |
| Table 3: | Cost and return analysis of groundnut production through Rhizobium inoculation |
Moreover, in all respects BAU strain of Rhizobium is better than BARI strain. Results of two years indicate that the costly nitrogenous fertilizer can be substituted by Rhizobium inoculum. Nitrogen is a chemical fertilizer while rhizobial inoculant is a natural biofertilizer which has no adverse effects on soil health and environment. Therefore, it can be suggested that rhizobial inoculant is a better substitute of chemical fertilizer nitrogen.