Volume 49, Issue 5
May 1959, pages 281-368
pp 281-286 May 1959
pp 287-302 May 1959
Indian rices belong to theindica group ofOryza sativa Linn. They are characterised by wide diversity in their morphological and physiological characters. They vary in duration from 85–200 days, in their adaptability to different climatic conditions from cultivation at sea-level to that, at an altitude of 4,000–5,000 feet. They vary in their adaptability to growing in different seasons of the year, and in growing under upland and deep water conditions. They also vary in their resistance to diseases, insect pests and drought. They exhibit wide variation in plant height, tillering, stiffness of straw, grain shedding habit, panicle length, size of grains as well as distribution of pigment on plant parts.
The main problem in rice is the production of high yielding varieties and about 445 improved varieties giving 12–20 per cent. enchanced yield have been evolved in different States by introduction, selection in natural populations and hybridization. Other problems which have received attention at the hands of rice breeders are the evolution of early maturing varieties; varieties responsive to heavy manuring; non-lodging and non-shedding varieties; varieties resistant to floods, salinity, drought, diseases and insect pests, as well as varieties with profuse tillering habit and higher milling out-turn. In all the above breeding projects the principles of heridity, variation and genetic recombination as well as the principle of differential response of genotypes under different environmental conditions, have been fully utilised for the improvement of the rice crop, and several varieties have been evolved or are in the process of evolution, to meet the different requirements.
pp 303-308 May 1959
Notwithstanding the fact that the post-war increase in the world rice acreage and production has exceeded the pre-war level, there is still a considerable world shortage in rice—a cereal that feeds more than half the world’s population. This is so because the growth of the rice-eating population is always out-stripping production. Production of rice should, therefore, be stepped up especially by those countries which still depend on imports.
By crossing eightIndica varieties of Andhra Pradesh with fourteen suitableJaponicas, in forty-four different cross-combinations, highly desirable progenies have been isolated in Andhra Pradesh. They gave up to one hundred and twenty-four per cent. higher yield (than the Andhra Pradesh parents) and are non-lodging and non-shedding. Their milling and cooking qualities are also good. Thus, the newIndica Japonica synthetics are likely to be acceptable alike to the farmer, the miller and the consumer.
For effecting further botanical improvement of rice, it is suggested that a very intensive programme of collection of rice varieties in theIndica region be pursued and these new collections bred and studied under conditions of high farming and fertilization. It is also suggested that these new improvedIndicas be crossed with appropriateJaponicas for isolating superior hybrids.
It is further suggested that radio isotopes as a source of radiation be employed for getting new and superior germplasm. Unless new germplasm is rapidly built up, both in theIndica andJaponica groups, the future course of hybridization may not be very fruitful. The present morphology, anatomy and karyology of the rice plant will have to be suitably modified to make it more efficient and useful for future generations.
pp 309-318 May 1959
Improvement in the seed is a permanent improvement with more lasting effects than any other method of agricultural improvement. The cultivators have taken up improved seed more readily than any other method of improvement. Hitherto the method of selection was followed extensively for the improvement of rice. It has its own limitations particularly with reference to manuring. It is discussed how theindica types do not show as much of response asJaponica types.
The possibility of improving by hybridization is discussed with reference to some of the inter-varietal and inter-racial crosses done in Orissa.
The work that is now in progress in the breeding ofJaponica×indica hybrids in Orissa is briefly stated. At present there are 27 crosses of different combinations under study in Orissa. Breeding for short and medium height withindica type of grain is in progress. The author could get successful combination of the above two characters in the crosses Asahi×T. 812 and Norin 6×T. 812. Some of the results obtained are presented. It is proposed to study the response of these fixed hybrids to different doses of manuring.
pp 319-330 May 1959
A large number of fertilizer experiments have been conducted in the country with an object to get a rationalised and economic programme of fertilizer for different areas. Results have shown that rice soils in India need both nitrogen and phosphate for increasing production. Response to potash application has however not been adequate enough. Nitrogenous fertilizers have been found most effective in increasing yield in almost all trials, but highly significant yield increases to phosphate application have been obtained only in a few localised areas in the country. In recent all-India trials conducted on cultivators’ fields, however, phosphate need is felt at many places. Green manuring, another rich source of nitrogen, has proved equally effective and sometimes better than inorganic fertilizers. Different nitrogenous fertilizers like ammonium sulphate, ammonium nitrate, ammonium chloride and urea have also been tested. At experimental stations, ammonium sulphate has generally proved more effective than urea and ammonium nitrate but in all-India T.C.M. trials on cultivators’ fields, results have been rather variable and not much difference between these sources of nitrogen carriers has been observed. Various phosphatic fertilizers tried are also not found different in their behaviour.
Time of fertilizer application, level and type of fertilizer and magnitude of response is found to vary widely from place to place. No relationship between the soil type and any of these factors has as yet been established. Available soil analytical data have also not thrown light on this aspect. In the absence of this, it becomes difficult to formulate fertilizer schedules and advisory standards for different areas. Apart from soil type, soil texture, drainage and soil water status in rice soils during the growth period may be considered responsible for such wide variation in fertilizer response. Great losses of nitrogen by leaching and denitrification occur when a rice soil profile left in aerated condition for a few days is submerged. Subsurface placement of ammoniacal fertilizer has been suggested as a rational method to reduce such fertilizer losses and increase fertilizer efficiency. Other examples of influence of soil water on fertilizer response by ammonium sulphate and urea are given and urea is considered more profitable, when used mixed with dry soil and flooded about 48 hours after application.
Physiological acid action of ammonium sulphate is not likely to play any important part in deterioration of soil fertility in water-logged soils, except under highly acid soil conditions. This is because of acid tolerance of rice crop and increase in pH of rice soil on flooding. Danger from ammonium sulphate may however arise due to sulphide injury in soils lacking in active iron and manganese.
Importance of soil-water relationship in fertilizer application in manurial trials is stressed and collection of data on soil water condition before and after fertilizer application and during critical growth condition of the crop up to flowering is suggested so that experiments under similar soil water patterns can be pooled for interpretation of fertilizer response. Separate investigations to study interaction of different soil water patterns with fertilizer response are also suggested. This may give useful information on which fertilizer schedules and advisory standards for different areas may latter be based.
pp 331-337 May 1959
Researches on wet paddy nutrition were conducted in the Division of Agricultural Chemistry of the former Hyderabad Government during 1950–56, on sandy loam to loamy red earths and clay loam to clayey black soils.
Following are the findings:—
(I) Both the above two types of soils were found to be very deficient in nitrogen and phosphoric acid and paddy crop would not at all grow without phosphoric acid application.
(II) although paddy crop (6 months crop) of an average weight of 4,000 lb. dry matter including paddy and straw takes up from one acre of the soil, only about 35 lb. of N, 9 lb. of P2O5 and 42 lb. of K2O, the actual manurial doses of N and P2O5 are more.
(III) On sandy loam red earth, the optimum dose of N, was 60 lb. per acre and N:P2O5 ratio varied from 1:½ to 1:1 with lower levels of N and at 60 lb. N level it was 1:½. On B.C. Soil, the optimum dose of N was 45 lb. per acre and N:P2O5 ratio was 1:¾.
(IV) Growth studies of a long duration crop (6 months crop) showed that the greatest (nearly 67%) increase in dry matter and over 61% nitrogen and potassium absorption occurs during reproductive stage. In contrast, the absorption of P2O5 is very gradual and only about 28% takes place during reproductive stage and the maximum being during the tillering.
In the light of the above findings, field experiments conducted on times of application of manures indicated that in B.C. clayey soil N and P may be conveniently applied at puddle to obtain maximum crop returns for a short duration paddy (120–125 days). In case of light soil, there is need of split application of N,i.e., half at puddle and half at 1st or 2nd weeding.
(V) Regarding method of application of fertilizers, smearing the seedlings roots with manure and mud-slush before transplanting gives about 20% more paddy yields on heavy B.C. soil. But the same method is not suitable for light red earth soil.
(VI)Other related factors affecting paddly nutrition.—(a) Nitrogen and phosphoric acid applied through fertilizers (ammonium sulphate and superphosphate) to paddy crop are not appreciably lost from the root zone through vertical drainage.
(b) Paddy can tolerate a concentration of 0·2% soluble salt (NaCl) in irrigation water. Salt concentration between 0·2 and 0·5% affects paddy yields considerably, and above 0·5% is almost fatal to rice.
(c) Although paddy is grown in standing water, it needs subsoil drainage. Under ill-drained conditions, rice crop manured with fertilizers containing sulphate suffers from sulphide injury to the roots which get coated with iron sulphide due to reduction of sulphate and formation of sulphide.
(d) Paddy crop suffers if green manured under ill-drained conditions.
pp 338-348 May 1959
The micronutrient requirement of rice and the quantities supplied through various sources is discussed. Unlike in the other cereals, the quantities of trace elements supplied through water, rain and irrigation, is considerable.
The problem of Mn toxicity often met with in the new ayacuts (black soils) under Tungabhadra Project is discussed in detail and remedial measures are suggested. Particular attention is drawn to natural build up of organic matter and nitrogen in soil subject to rice cultivation. The role of organic matter in increasing the availability of iron is dealt with.
Visual symptoms, chemical analysis and tissue tests for diagnosing Mn toxicity are fully described.
The status of boron and copper in the black soils under Tungabhadra Project is still to be ascertained.
pp 349-362 May 1959
The diseases of rice are estimated to cause annually about 10 per cent. loss in rice production. The more important diseases are “blast,” “helminthosporiose,” “stem rot” and “foot rot”. Of these “foot rot” can be checked successfully by treating the seeds with organo-mercurial fungicides and this method is now widely adopted whenever foot rot is prevalent in the country. “Blast” is the most destructive of the diseases and is of widespread occurrence. Research on the control of the diseases is directed towards evolution of highly resistant varieties, development of economic spraying and dusting schedules and the study of the factors favourable for disease development. There is need to intensify the programme of breeding resistant varieties in the country, as the cultivation of resistant varieties is the most economical method of control of the diseases. But since many resistant varieties are not presently available, plant protection by fungicidal spraying and dusting has to be resorted to, to save the crop against the damage caused by diseases. Economic spraying and dusting schedules have already been worked out for blast disease and they have to be popularised. For successful and large-scale adoption of plant protection measures, it is necessary to link the same with an efficient forecasting service. This has still to be organised in India.
pp 363-368 May 1959
With increased rice production under improved methods, the problem of plant protection is more accentuated. Insect infestation is found to be more in rice under high fertility. The usual indirect methods advocated till now, have not achieved the expected results. Chemical method of control appears to be the most effective at present. Insecticidal control of pests that feed on the foliage of the plant is comparatively easier. In the case of pests that remain concealed during their destructive phase, the choice of a suitable insecticide, the method and time of application of the insecticide seem to be the deciding factors in achieving effective control. At the Central Rice Research Institute, stem borers and gallfly have been effectively controlled by timing the application of insecticides to synchronise with the pest emergence. In the case of stem borers, a set of two sprayings is necessary at the time of brood emergence. The first spray kills the moths and checks oviposition while the second one, given 8–10 days later, kills the newly hatched larvæ before they bore into the stem. In the case of gallfly, spraying four times during the vegetative phase of the crop to synchronise with brood emergence reduced the incidence considerably. Yet insecticidal method can only be an adjunct or complementary to other methods of pest control. Biological control of these pests needs to be fully explored for a practical solution of the problem. Establishment of a pest warning organization is an immediate necessity to enable cultivators to take suitable pest control measures in time on a co-operative effort.