Abstract: The aim of this study to evaluate three biological preparation on rice at Puducherry condition. The efficiency of biofertilizers (Azospirillum and BGA) in an integrated manner on few ruling rice varieties was experimented in Puducherry, UT, India in both upland and lowland conditions, during 2005-2006 for three seasons. The results proved that there was a gradual increase in the efficiency of biofertilizer and its compatibility with inorganic fertilizers. Significant difference in the soil fertility status (available N, P and K) and the soil biota has increased in the plots treated with the biologicals in the later stage (the third season).
INTRODUCTION
Sustainable crop yield can be obtained with efficient use of available land and water (Krol, 1999) and judicious integration of organic and mineral fertilizers (Singh et al., 2002). Azospirillum, BGA and Azolla multiply fast, decompose and substitute N fertilizers up to 25% of the total crop requirement (Patel, 1998) thereby play a vital role in promoting rice productivity (Gupta et al., 1989). Here in Puducherry rice has been cultivated for 3 seasons of an year using chemical fertilizers alone, which deteriorates the soil and induces more pests and diseases. Despite the fact that microbial inoculants have long been incorporated into field practices worldwide, most of them have been used and evaluated on the legumes and to a lesser extent on cereal crops (Hedge and Brahmaprakash, 1992; Fages, 1994; Tang and Yang, 1997; Bashan, 1998; Gnanamanickam et al., 2002). Hence, the current study was undertaken to evaluate three biological preparations on rice at Puducherry conditions.
MATERIALS AND METHODS
The present study focuses on the effect of Azospirillum and BGA with 25% replacement of N chemical fertilizer (individual and/or in combination) on the yield of ruling rice varieties, ADT 37, IET 1444, CO 47 (low land) and ADT 37, White Ponni and Chinna Ponni (up land system) in three cropping seasons during 2005-2006, namely, Spring-Summer (April-July), Autumn-Winter (August-January) and Winter-Spring (January-April) in Melsathamangalam and Sorapet villages of Puducherry where mono cropping (rice) is practiced. Recommended doses of P and K were applied basally after soil testing. The trials were carried out in a Randomized Block Design with four replications each and the treatment were as follows: T1-Control; T2 - 100% NPK through inorganic fertilizer; T3 - 75% N through inorganic fertilizer; T4- T3 + Azospirillum; T5 - T3 + BGA; T6 - T3 + Azospirillum + BGA. Grain yield (kg/acre) and the soil fertility status (nutritional and microbial) were analyzed.
RESULTS AND DISCUSSION
Effect of Biofertilizers on Grain Yield and Fertility Status in Lowland
System
The results (Fig. 1) indicated that in the lowland system,
in the initial stages (Spring-Summer), the inorganic fertilizer (100%) resulted
in the highest yield (2088 kg/acre in ADT 37), compared to others. A slight
change was observed in the second crop, where T3 showed the highest
yield followed by T2 and T4, with no significant difference
between them. However, in Winter-Spring season the yield of CO 47 in T6
was on par with T2 and T3 (1200, 1231 and 1193 kg acre-1).
It shows a gradual increase in the efficiency of biological and its compatibility
with inorganic fertilizers. Similarly repeated usage of phosphobacteria along
with inorganic fertilizers resulted in higher crop value (Santhi and Selvakumari,
1999). High level of NPK was observed before harvest but later the nutrients
declined (Table 1). This opined with Chinnusamy et al.
(2006) wherein the microbial inoculants, blue-green algae, phosphate-solubilizing
bacterium, vesicular-arbuscular mycorrhizal fungus positively interacted with
one another and resulted in significant improvement in yield and nutritional
parameters. Application of biofertilizers also substantially improved soil (peat)
fertility status by increasing the nitrogen (N), phosphorous (P) and organic
carbon content in the paddy crop.
| Table 1a: | Nutritional status of soil at pre and post harvest stages |
| Each value mean of 4 replicates, The common letter(s) shared in each row do not differ significantly as per DMRT at 5% level, (1a) Upland; (1b) Lowland; T1: Control; T2: 100% NPK Inorg. Ferti; T3: 75% N Inorg. Ferti; T4: 75% N Inorg. Ferti. + Azospirillum; T5: 75% N Inorg. Ferti. + BGA; T6: 75% N Inorg. Ferti. + Azospirillum + BGA | |
| Fig. 1: | Effect of biofertilizers on rice yield in lowland system, T1: Control; T2: 100% N Inorg. Ferti; T3: 75% N Inorg. Ferti; T4: T3+ Azospirillum; T5: T3 + BGA; T6: T3 + Azospirillum + BGA |
| Fig. 2: | Effect of biofertilizers on rice yield in upland system, T1: Control; T2: 100% N Inorg. Ferti; T3: 75% N Inorg. Ferti; T4: T3+ Azospirillum; T5: T3 + BGA; T6: T3 + Azospirillum + BGA |
| Table 2a: | Microbial analysis of soil pre and post harvest stages at trial plots |
| Each value mean of 4 replicates, the common letter(s) shared in each row do not differ significantly as per DMRT at 5% level, (2a) Upland; (2b) Lowland T1: Control; T2: 100% N Inorg. Ferti; T3: 75% N Inorg. Ferti; T4: T3+ Azospirillum; T5: T3 + BGA; T6: T3 + Azospirillum + BGA | |
Effect of biofertilizers on grain yield and fertility status in upland system
The results of Fig. 2 show positive correlation between
the usage of microbes and consistent increase in crop yield. The highest yield
during first season (Winter-Spring-Chinna Ponni) was observed in T2
(1289 kg acre-1), while in the subsequent two generations, T6
recorded highest yield (1705 and 1400 kg acre-1 respectively) followed
by T5 and T4. This compatibility and integration of microbes
with inorganic fertilizers and its role in enhancing the yield of rice closely
resembled with earlier research by Martin (2000) and Choudhury and Kabi (2003).
Further, as per Vasudevan et al. (2002) the bacterial formulations have
direct impact on grain yield (1000-grain weight).
The nutrients N, P and K got enhanced after post harvest stage (Table 1) indicates the steady increase in the fertility status and water-holding capacity of the soil due to the residual effect (Dey and Paul, 1999; Kumar et al., 2000).
Microbial Analysis
Though there was not much difference in the initial stages, the microbial
population increased due to repeated application of biologicals and organic
matter. Similarly, organic amendments such as vermicompost from household solid
waste, horse and rabbit manure and chicken manure resulted in higher soil organic
carbon (Ferreras et al., 2006). In the upland system, T5 and
T6 exhibited more number of bacterial and actinomycetal colonies,
whereas a definite correlation has not been arrived in the case of lowland (Table
2).
CONCLUSION
The experimental results proved that the biofertilizers play a major role in improving the soil fertility and thereby increase the crop yield. In addition, it improves the soil biota and minimizes the sole use of inorganic fertilizers and the cost of cultivation.
ACKNOWLEDGMENTS
The authors acknowledge Department of Biotechnology, New Delhi, for funding and the farmers of two villages for their participation.