NITROGEN UPTAKE BY THE RICE CROP IN THE EXPERIMENTS WITH BLUE-GREEN

ALGAE

BY DR. M. N. SAHAY (Central Rice Research Institute, Cuttack)

Received May 7, 1965

(Communicated by Dr. R. Subrahmanyan, v.A.sc.)

INTRODUCTION

INVESTIGATIONS have been under progress at the Central Rice Research Insti- tute, Cuttaek, since 1961 on the r61e of blue-green algae in augmenting the fertility of rice soils and for increasing rice production. Some of the results have already been reported (Relwani, 1963, 1965; Relwani and Subrahmanyan, 1963; Relwani and Manna, 1964; Subrahmanyan et al., 1964 a, b, 1965). The nitrogen-fixing capacity, the extra-cellular nitrogen liberated and organic matter produced have also been investigated (Subrah. manyan and Sahay, 1964 and 1965). There are no reports so far on the uptake of nitrogen by the rice crop in such trials. The present work was, therefore, undertaken in some of the above experiments to assess the quantity of N uptake by the crop as a result of the r61e of the indigenous as well as introduced mixture of nitrogen-fixing blue-green algae.

MATERIAL AND METHODS

Samples of straw and grain were collected after harvest from the field and pot experiments during three consecutive seasons (1962 main crop, variety C.R.T.141 ; 1962=63 second crop, variety Ptb.lO; and 1963 main crop variety C.R.T.141).

Nitrogen in these was estimated on duplicate samples from all repli- cates by rnicro-kjeldahl method. There were nine treatments with four replicates in the field and five replicates in the pots each season. From the percentage of nitrogen and the resFective yield data the uptake of nitrogen in the field and pot crops was calculated.

Algal inoculation and other treatments were given in the field and pot only during three seasons, 1962 main crop, 1962-63 second crop and 1963

223

224 M.N. SAHAY

main crop, thereafter no treatment was given in order to study the residual effect of algae during 1963-64 second crop (variety Ptb.lO) and 1964 main crop (variety C.R.T.I41).

The nitrogen percentages of grain and straw of 1962-63 second crop and the mean of the nitrogen percentages of samples of 1962 and 1963 main crop were utilised with the yield data of the residual crop of 1963-64 second crop and 1964 main crop respectively in fields and pots for assessing nitrogen uptake in the residual effect studies. The nitrogen in the chaff has not been estimated ; therefore, the figures are only a conservative estimate of the nitro- gen contribution by the blue-green algae. The results have been analysed statistically.

The material for the studies has been the yield in the experiments con- ducted at the Central Rice Research Institute already published (Relwani and Subrahmanyan, 1963; Subrahmanyan et aL, 1965).

RESULTS AND DISCUSSIONS

The results of the nitrogen uptake of the field and pot experiments of the three seasons are presented in Tables I and II respectively.

Field Experiments The treatment LB (control + algae) showed a non-significant uptake

of 1- 56 kg.N/ha, and 3.19 kg.N/ha., and a significant uptake of 6.19 kg.N/ha in 1962 and 1963 main crops and 1962-63 second crop respectively over control (LA).

The treatment NB (rabbing + algae) showed a highly significant uptake of 4.73 kg.N/ha, in 1962 over treatment NA and was at par during 1962-63 and 1963.

The treatment MA (fertiliser mixture : lime + super phosphate + trace of sodium molybdate--indigenous flora) showed a highly significant uptake of 8-03, 8.18 and 11.49 kg.N/ha, in 1962, 1962-63, and 1963 over control (LA).

The treatment MB (fertiliser mixture + algae) also showed a highly significant uptake of 13.75, 13.73 and 23.42 kg.N/ha, over control LA during three seasons in order.

A comparison of the treatment MB over MA showed a highly significant uptake of 5.72 and 11-93 kg.N/ha, in 1962 and 1963, and a significant uptake of 5" 55 kg.. N/ha. in 1962-63,

• Vitrogen Uptake by Rice Crop in Experiments with Blue-Green Algae 225

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Nitrogen Uptake by Rice Crop in Experiments with Blue-Green Algae 227

In terms of ammonium sulphate the treatments showed a nitrogen appli- cation equivalent of 24.70, 23-30, 45.42 for MA and 42.30, 37.10, 92.56 for MB, kg.N/ha, in 1962, 1962-63 and 1963 respectively.

It may be seen from the above that the effect of introduced flora was almost double that of the indigenous flora. When a comparison of the nitrogen uptake of both the treatments MA and MB is made during the three seasons, the uptake of N showed a gradual rise which would indicate a gradual fertility build up; in other words, this indicates that the N fixed and the organic matter added by the blue-green algae during the successive crop season increase progressively. It may be mentioned that it is only the extra-ceUular nitrogen that is utilised during the growth of the crop and considerable organic matter and nitrogen are left behind for the next season crop (Subrahmanyan and Sahay, 1964).

The treatment OB (rabbing + fertiliser mixture + algae) showed an uptake of N at par in 1962 and 1962-63 and significantly supeIior in 1963 over the treatment CA (fertiliser mixture + rabbing). As stated above, this also indicates a fertility build up by the introduced blue-green algae.

All the treatments except treatment LB in 1962 and 1963 main crops which were at par showed a significantly higher uptake over control (LA) in the three seasons.

A comparison of the treatments M to O (A and B) with treatment P (ammonium sulphate at 20 kg. N/ha.) shows that the treatments N (A and B) and MA were at par and that the treatment O (A and B) and MB significantly superior in 1962. In 1962-63, all the treatments were at par except MB which was significantly superior. In 1963 the treatments N (A and B) and LB were at par and the treatments M (A and 13) and O (A and B) were significantly superior to ammonium sulphate. The only exception was treatment LB in 1962 which was significantly inferior to treatment P.

Pot Experiment A similar trend may be seen in the results of the pot experiment conducted

simultaneously during the same seasons (Table I1). The treatment LB (control + algae) gave a non-significant uptake of

2.6, 19.0 and 5.8 rag. N/pot being at par with the control (LA) during 1962, 1962-63 and 1963.

The treatment NB (rabbing + algae) was at par with the treatment NA (rabbing) during all the three years and gave a non-significant increase of 93.1 nag. N/pot only during 1963.

228 M.N. SAHAY

The effect of the treatments MA over treatment LA (control) was not significant~ Nevertheless, it showed a progressive uptake of 2.2, 43.5 and 90.5 rag. N/pot during 1962, 1962-63 and 1963 respectively.

Similarly, the treatment MB gave a significant increase of I01-2 rag. N/pot in 1962 and highly significant increase of 211.7 and 457-0 rag. N/pot in 1962-63 and 1963, indicating a progressive ~nerease in the fertility of the soil.

A comparison of the treatment MB (fertiliser mixture -k algae) over/VIA (fertiliser mixture q- indigenous flora) showed a significant uptake of 99.0 and a highly significant uptake of 168.2 and 366.5 rag. N]pot uptake during 1962, 1962-63 and 1963. It is clear from the above that both the indigenous flora and introduced flora show a gradual fertility build up. In both the treatments the high uptake in 1963 starting from a low value in 1962 is explainable on similar lines as in field experiment.

The treatment OB (rabbing + fertiliser mixture + algae) gave a non- significant increase of 17.8 and 7.3 and a significant increase of 174.5 rag. N/pot uptake during 1962, I962-63 and I963 respectively over treatment OA. Thus a gradual fertility build up is seen by the introduced algae when rabbing and fertilisermixture are given as basic treatment.

When compared with ammonium sulphate the treatment LA in 1962-63 and treatments L (A and B) in 1963 were significantly inferior. The treat- ments O (A and B) and N (A and B) in 1962, MB, O (A and B) and N (A and B) in 1962-63, and OB and MB in 1963 were significantly superior to ammonium sulphate. The rest of the treatments in the respective years were at par. It is interesting to note that the treatment MA is seen to be at par and the treatment OB to be significantly superior to ammonium sulphate. It is also interesting to note that the treatment MB (except in 1962) is seen to be superior to ammonium sulphate. Likewise, the effect of the treatment MB over MA (except in 1962) was significantly superior to ammonium sulphate and increases progressively.

RESIDUAL EFFECT STUDIES

The results of the residual study from field and pot are presented in Tables III and IV respectively*.

* In these studies, the soil concerned was puddled and the seedlings just planted; none of the treatments was applied except ammonium sulphate to the field/pot concerned at 20 kg.N/ha., for comparison.

Nitrogen Uptake by Rice Crop in Bxperiments with Bhle-Green Algae 229

Field Experiments (Table III)

The uptake of N in the treatment LB was at par with treatment LA during 1963-64 and 1964 respectively. The treatment NB was also at par with the treatment N A during both the years.

TABLE III

Total nitrogen uptake in field experiments in kg.N]ha--residual study

1963-64, Second season 1964 Main crop Vat. Ptb.lO Var. C.R.T.141

Nitrogen Nitrogen Treatments

Total Over control Total Over control LA L,4

A B A B A B A B

L. Control(Check) 14.98 15.29

M, Lime, 1000 kg./ha, + Superphosphate at 20 kg. P~OJha. + Sodium molyb- date 0. 28 kg./ha. 13.85 17.57

N. Rabbing 15-17 14.35

O. N + M 17.30 14.55

P. Ammonium sulphate at 20 kg.N/ha. 17.51 ..

C.D. at 5~0

.. 0"31 47.6 44-8

• . 2"59 41.9 45.9 . . . .

0-19 .. 48.1 46.7 0-5 ..

2"32 .. 46.9 47.7 .. 0-1

2"53

2"61

45"9

A--Without algae. B--With algae.

The treatment M A gave an uptake of 41.9 kg.N/ha, in 1964 against 13"85 kg.N/ha, in 1963-64. Similarly, the treatment MB showed an uptake o f 4 5 . g k g . N / h a , in 1964against 17. 57 kg.N/ha, in 1963-64 and both the treatments were at par with control LA.

230 M.N. SAHA¥

The treatment MB over MA showed a significant increase of 3.72 kg. N/ha. in 1963-64 and a non-significant increase of 4-0 kg.N/ha, in 1964. Art interesting point to note here is that there is a little but progressive increase in 1964 over the previous year Ievealing a similar trend as in the field experiments described earlier (Table I).

The treatment OB gave a significantly lower uptake over OA in 1963-64 but a slightly higher non-significant uptake in 1964.

When compared with ammonium sulphate the treatments NB, MA and OB were significantly inferior and the rest were at par in 1963-64. As pre- viously stated, though the treatment MB was not significant, yet it appears to be bettor than ammonium sulphate.

The treatment effects were not significant in 1964. It may be mentioned here that in 1964 the fields due to heavy rains were covered with a sheet of water thus enabling the n-fixing blue-green algae to spread all over; in fact, several nitrogen-fixing blue-green algae were found in all the plots (Subrah- manyan et aL, 1965).

Pot Experiment (Table IV)

The treatment LB was statistically at par with the treatment LA in 1953-54 and 1964 respectively.

The treatment NB though showing a higher uptake over NA, was statis. tically at par in both the years.

The treatment MA over LA was highly significant in 1963-64 and was at par in 1964. The treatment MB over LA showed a highly significant uptake of 183.6 mg. N/pot and 77.0mg. N/pot in both the years.

The treatment MB over MA showed a highly significant uptake of 89.3 rag. N/pot in 1963-64 and was at par in 1964, though non-significant but superior.

The treatment OB was not statistically superior to OA; however, it shows an improvement in both the years.

When compared with ammonium sulphate n o n e of the treatments was statistically inferior in both the years. The treatment M (A and 13) and O (A and 13) were significantly superior and the rest were at par in 1963-64 and the treatment MB statistically superior to ammonium sulphate and rest at par in 1964. Though the treatment MA and O (A and B) in 1964 were statistically at par, the latter was better.

Nitrogen Uptake by Rice Crop in Experhnettts with Bhte Green-Algae 231

TABLE IV Total nitrogen uptake in pot experiments in mg. N/pot--residual study

1963-64, Second season 1964 Main crop Var. Ptb.lO Var. C.R.T.141

Nitrogen Nitrogen Treatments

Total Over control Total Over control LA LA

A B A B A B A B

L. Control(Check) 109.5 110.8 .. 1.3 133-0 127.3 . . . .

M. Lime, 1000 kg./ha. q- Superphosphate at 20 kg. PzOJha. q-Sodium molybdate 0. 28 kg./ha. 203-8 293-I 94.3 183.6 171.6 210.0 38.6 77.0

N. Rabbing 128.7 143.3 19.2 33"8 110.7 114.8 . . . .

O. N + M 246.3 258.1 136.8 148.6 180.5 187.1 47,5 54.t

P. Ammonium sul- phate at 20 kg.N/ha, t29.8 .. 20- 3 ,. 146.9 .. 13-9 ..

C.D. at 5~o 55.8 54.4 C.D. at 1~o 75.1 73-1

A--Without algae. B--With algae.

GENERAL REMARKS

The result of the experiments and their residual effects shows that the treatment LB over LA appears to be at par in most of the experiments except in the 1962-63 field trial where it was superior. The treatment NB over NA was also at par in most cases except in 1962 field experiment when it was superior. The treatmellt 2VIA over LA was highly sigrtificant in 1962, 1962-63 a~ld 1963 in the field experhnents and 1963-64 pot experiments and the rest of them were at par. The treatments MB over LA was highly signifi- cant in most cases except in 1962 pot experinaent where it was signifieanl

232 M.N. SAHAY

at 5~o level. The only exception was field experiment of residual study where it was at par.

The tendency for a gradual fertility build up in all the treatments is brought out in the experiments.

When compared with ammonium sulphate the treatment MB was superior except in 1962 pots. In the residual crop in the field, it was at par. The treatment MA was superior in 1963 field experiment and in 1963-64 pot experiment. The treatment O (A and B) was superior in 1962 field and pot and in 1963 field and in 1962--63 and 1963-64 pot experiments. In the 1962-63 field and 1963 pots only the treatment OB was superior. The treatment N (A and B) was superior in pots in 1962 and 1962-63.

An analysis of the above shows that the treatment MA (indigenous flora) is at par with ammonium sulphate and even superior in the succeeding seasons in the field (Table I). The treatment MB (fertilizer mixture + intro- duced algae) proved to be superior in most cases as also the treatment OA (rabbing + fertiliser mixture). The best result was obtained with treatment OB (tabbing + fertiliser mixture + introduced algae).

SUMMARY

The results of the nitrogen uptake as influenced by the nitrogen-fixing capacity and organic matter added by blue-green algae during three crop seasons are presented on the basis of field and pot experiments. An estimate of the nitrogen contribution in the study of the residual effect of blue-green algae has also been made.

It is seen that by conditioning the soil (addition of fertilizer mixture) for manifestation of the indigenous flora, N uptake upto 20 kg.N/ha. (supplied as ammonium sulphate) could be achieved.

The treatment fertiliser mixture + tabbing was also superior to ammo- nium sulphate at 20 kg.N/ha. The best result was obtained with rabbing + fertiliser mixture + algae. The results obtained from the several treatments indicate that blue-green algae (indigenous flora and/or addition of N-fixing species) could be effectively utilised for rice culture and as a substitute for ammonium sulphate under certain conditions.

ACKNOWLEDGEMENT

The author thanks Dr. R. H. Richharia, Director, Central Rice Research Institute, for his keen interest in the work and encouragement. I thank

Nitrogen Uptake by Rice Crop in Experiments with Blue-Green Algae 233

Dr. R. Subrahmanyan, Botanist, for unfailing guidance in this work and in the preparation of this paper. Thanks are due to Shri L. L. Relwani, Shri G. B. Manna for much help diaring the work and Shri A. K. Ghosh for help in the statistical analysis.

REFERENCES*

Relwani, L. L.

~ - - and Manna, G. B.

Relwani, L. L. and Subrah- manyan, R.

Subrahmanyan, R., et al.

and Sahay, M. N.

. . "R61e of blue-green algae on paddy yield," Current Sci., 1963, 32, 417-18.

. . "'Response of paddy varieties to blue-green algae and methods of propagation," Ibid., 1965, 34.

•. "Effect of blue-green algae in combination with urea on paddy yield," Ibid., 1964, 33, 687.

'" Rrle of blue-green algae chemical nutrients and partial soil sterilization on paddy yield," Ibid., 1963, 32, 441-43.

.. "Observations on the r61e of blue-green algae on rice yield compared with that of conventional fertilizers," Ibid. 1964 a, 33, 485-86.

.. "Rble of blue-green algae and different methods of partial soil sterilization on rice yield," Proc. Ind. Acad. ScL. 1964 b, 60B, 293-97.

. . "Fertility build up of rice field soils by blue-green algae," Proeo Ind. Acad. ScL, 1965. 6213, 252-72.

. . "Observations on nitrogen-fixation by some blue-green algae and remarks on its potentialities in rice culture," Proc. Ind. Acad. ScL, 1964, 6013, 145-54.

. . "'Observations on nitrogen-fixation and organic matter pro- duced by Anabaena circinalis Rabh. and their significance in rice culture," Proc. Ind. Acad. Sci., 1965, 61B, 164--69.

* References to earlier work may be found in Relwani and Subrahmanyan, J963 and Subrahmanyan and Sahay, 1964.