AGRONOMY

Studies on rice in relation to its environment with suitable modifications of some of the environmental conditions which govern maintenance of soil fertility, water use and availability of nutrients to plants with a view to improve the cultural practices for maximizing rice production have been the objectives of agronomy division.

Pre-semi-dwarf area

Prior to the introduction of high-yielding semi-dwarf varieties, the optimum levels of major nutrients and comparative efficiency of different manures and fertilizers and the appropriate time and mode of fertilizer application for harvesting maximum rice were determined with tall varieties. Evaluation of Indian and exotic rice varieties and new selections evolved at CRRI for yield under different manurial and cultural practices and in limited coordinated trials in different climatic and soil conditions was an important activity of the division. Some early maturing Chinese varieties suitable for certain areas were identified. The variety CH 1039 almost completely replaced the local varieties in Kashmir valley and is an example for successful plant introduction as it is cultivated in some pockets even to-day.

Permanent manurial trials, have revealed the fact that continuous application of ammonium sulphate to the same plot does not leave any beneficial or deleterious residual effect on soil fertility. Similarly, application of lime did not affect grain yield. There was no response for the application of phosphatic and potassic fertilizers. On the other hand, continuous application of compost showed a significant cumulative residual effect on the fertility status of the soil.

The beneficial effect of deep placement of ammonium sulphate in the waterlogged rice soils (capable of giving a response of 14-18 kg rice for every kilogram of nitrogen compared to 8-9 kg rice for every kilogram of nitrogen in surface application) and fractional application of ammonium sulphate in three splits coinciding with the vegetative growth phase in the early stage and the flower initiation phase at the later stage for the transplanted crop were established.

Due to inadequate control of irrigation and drainage, successive cultivation of rice in wetlands was the general practice. The division has played a significant role in determining the schedule of planting and identifying the sequence of varieties for an economic rice-based cropping system. These efforts demonstrated the feasibility of economically growing cotton, groundnut, gram, greengram, wheat and linseed in sequence with rice under irrigated conditions. In addition, possibility of growing two crops of rice in succession during a year with a green manure crop in between was shown in areas where irrigation facilities are available and the winter temperatures are not low. Under irrigated conditions, possibility of successfully growing three crops of rice constituting early, medium and early duration varieties in succession was also determined. Introduction of jute in rotation with rice was shown to be highly economical.

Semi-dwarf area

With the introduction of high-yielding, semi-dwarf varieties in mid-sixties, comprehensive investigations were undertaken to devise ideal management practices for realizing maximum rice yield. Agronomic practices for growing high-yielding varieties developed at this institute have been adopted in the country for increasing rice yield. These form the basis for high production of rice till date.

Management of irrigated rice

Varietal identification

Varietal evaluation has shown that cultivars Savitri (Ponmani) and Gayatri evolved in mid-seventies at CRRI were found promising for the wet season with an yield potential of 7 t/ha. Cultivars like Ratna, Annada and Udaya developed at CRRI and IR 36 showed promise with an yield potential of 5 to 6 t/ha in the dry season.

Water management

Water management studies were carried out exclusively for high yielding varieties. Realizing the fact that the actual benefit of high yielding varieties can be harvested in the dry season, when the duration of sunshine hours is more but water availability is limited, it was felt that determination of irrigation schedules that involve the use of minimum water without seriously affecting yield would go in a long way to increase dry season rice area. Based on the finding that percolation accounts for 50 to 60% of the consumptive use, studies were initiated to minimize this loss. This study revealed that irrigation schedules that alternate wetting and drying or saturation till tillering followed by maintenance of 5 to 8 cm water thereafter could save 50% of water as compared to continuous submergence without affecting the yield. Since rice is subjected to different degrees of flooding in wet season, a series of investigations were also taken up to assess the tolerance of different high yielding varieties to submergence at different growth stages. Cultivars like Jagannath and Vijaya tolerated water depth of 30 cm form the third week of growth onwards.

Studies on relationship between ET and open pan evaporation showed that at initial stages of crop growth ET was close to open pan evaporation, but at flowering, it was about 1.5 times than open pan evaporation, when open pan evaporation was 5.5 to 5.6 cm/day. Studies conducted on drainage aspects revealed that drainage was necessary in lowland rice only at early tillering stage. During dry season, application of water could be delayed till complete disappearance of ponded water.

Fertilizer management

The optimum nitrogen level for the majority of the high yielding varieties was 80 to 100 kg N/ha in the wet season and 120 to 150 kg N/ha in the dry season. Application of one-half the nitrogen at planting and the rest in two equal splits at 21 days after planting and panicle initiation stages proved beneficial.

Since there is yield plateauing in irrigated rice, efforts were made to spell out appropriate management practices for yield maximization. Highest yield of 7 t/ha was produced with the variety Gayatri in the wet season, where green manuring (S. aculeata) was done in situ to supply 5 t green matter/ha coupled with 33% extra plant population (15 x 15 cm spacing) and 33% extra fertilizer used (120:53:53 kg N, P2O5 and K2O/ha) coupled with the use of insecticide treated seedlings.

Crop modeling for nitrogen application

The ORYZA-O model was used for optimizing fertilizer nitrogen application programme for irrigated rice. the crop and soil input parameters for this model were derived from field experiments. Native soil nitrogen supplying capacity influenced these parameters. The response of the crop as found by numerical optimization represented the maximum attainable biomass calculated on the basis of radiation, crop parameters and soil parameters. The maximum simulated biomass accumulation was 23.6 t/ha at 325 kg N/ha in the highly fertile soil, whereas in the soil of low fertility status, the biomass was 15.3 t/ha at 200 kg N/ha. The optimum dose of nitrogen application in the dry season was computed to be 120 kg N/ha. The timings of application indicated that most of the fertilizer nitrogen should be applied before the panicle initiation stage. At low nitrogen input levels (20-40 kg N/ha) results suggested fertilizer nitrogen application around panicle initiation stage. The optimization by ORYZA-O did not suggest any basal application of nitrogen in these soils.

Field experiments were conducted to test the superior effect (if any) of the timing of fertilizer nitrogen application based on ORYZA-O model. Higher crop biomass, nitrogen uptake and grain yield of rice would be obtained at optimum nitrogen application level of 120 kg N/ha than other application levels when model-based timings were followed.

Weed management

The loss in yield due to unchecked weed competition (mostly from sedges and dicots) was 30 to 40% in direct-sown rice on puddled soil and 10-15% in transplanted rice grown in dry season. Several pr-emergence herbicides were evaluated for their bio-efficacy in these systems. The herbicides, butachlor, thiobencarb, avirosan, pretilachlor (with safener) at 0.75-1.0 kg /ha and anilofos at 0.4 kg /ha controlled the weeds effectively.

Management of Basmati-type scented rices

The possibility of growing newly developed scented Basmati-type rices in Orissa for augmenting farmers’ income was explored. Varieties, Kasturi, Ranbir Basmati and IET 8579 performed well both in dry and wet seasons with yields around 2.5 t/ha. These varieties responded up to 60 kg N/ha in wet season and up to 90 kg N/ha in dry season. The optimum population requirement in wet season ranged from 33 to 50 hills/m2. Early planting in July gave 13% higher yield over delayed planting in September.

Management of rainfed uplands

Varietal identification

Evaluation of varieties for upland situation revealed that Kalinga III and Vanaprabha maturing in 85 and 95 days, respectively, were suitable for lateritic and alluvial soils. These have an yield potential of 2.0 to 2.5 t/ha when grown with 30 to 40 kg N, 20 to 25 kg each of P2O5 and K2O/ha, and were recommended for low rainfall areas. For areas with an annual rainfall of 1100 mm and above, varieties Annada and Annapurna with an yield potential of 2.5 to 3.5 t/ha were suitable.

Stand establishment

Where rainfall in May is adequate for land preparation, seeding in June as soon as a rainfall of 50 to 60 mm is received was ideal and the crop of short duration rice matured by the end of September before monsoon waves off.

In uplands drilling with a seed rate of 40 to 60 kg/ha in rows 20 cm apart has been shown to be adequate and enabled adoption of better weed control and fertilizer practices. This practice also saves a lot of seed.

Fertilizer management

With the present day price of fertilizers and rice, a rate of 30 to 40 kg N/ha with a ceiling of 60 kg N/ha in upland is considered optimum and may give grain yields in the range of 2.5 to 3.5 t/ha with a benefit/cost ratio of 4 to 5.

Withholding basal application of N, application of 50 to 60% of N at three weeks stage and incorporation into soil, 20 to 25% when the crop is 40 to 45 days old and rest at boot leaf stage gave grain responses ranging from 26 to 54 kg per kg N (depending on rainfall patterns), with an average of 37 kg grain per kg N.

Where high-yielding varieties are regularly grown, application of 15 to 20 kg each of P2O5 and K2O was shown to be beneficial.

Cropping system

In areas where September rains and October rains do not normally fail (and the total rainfall is of the order of 450 mm), it was found possible to grow on these lands a winter crop like safflower, horsegram, mustard, niger and blackgram, provided they are sown not later than mid-October. Inter-cropping of rice with pigeonpea (1:4) proved beneficial as an insurance against crop failures.

Management of rainfed lowlands

Studies on management of rainfed lowland rice initiated during 1979 were carried out under four categories of lowlands; shallow (0-30 cm), intermediate-deep (0-50 cm), semi-deep (0-100 cm) and deep water (>100 cm), in simulated situations.

Shallow submerged lowlands (0-30 cm)

Varietal identification

Evaluation of varieties for growing in the wet season showed the suitability of Savitri (Ponmani), CR 1011, CR 1016 and Gayatri, which possess an yield potential of 5 t/ha and are capable of responding up to 80 kg N/ha, for areas where water depth does not exceed 20 cm. CR 683-123, IET 6080, CR 673-475 and Gayatri were found suitable for late planting during mid-September for harvesting with an yield of 4 t /ha.

Stand establishment

The advantage of skip-row method of planting (skipping one row after every three rows) at 15 cm apart saved 25% of the cost of fertilizer and transplanting with a semi-tall cultivar like Mahsuri at higher level of nitrogen (80 kg N/ha) in the wet season.

Transplanting late maturing semi-dwarf varieties (155 days) by mid-August either with 30 or 60-day-old seedlings produced similar grain yield, while aged seedlings of 60 days was superior to 30-day-old seedlings for delayed planting by mid-September. A grain yield of 3 t/ha was obtained by planting in the third week of September with a spacing of 15 x 15 cm (44 hills/m2) and with application of 60 kg N/ha. However, for timely planting in July, a spacing of 20 x 20 cm (25 hills/m2) was found to be optimum.

 Fertilizer management

Semi-dwarf varieties responded up to 80 kg N/ha. However, the economical level of nitrogen application was 40-60 kg N/ha. The response of high-yielding varieties under transplanted condition to split application of nitrogen was similar to the schedule worked out earlier with tall varieties.

Relative efficiency of urea super-granules (USG) and prilled urea (PU) in long duration rice in shallow lands.

Treatment

No of years

Grain yield (t/ha)

Response

 

tested

Treatment

Control

(kg grain/kg N)
29 kg N/ha - PU basal

9

3.7

3.3

12.8

29 kg N/ha - PU splits

10

3.8

3.3

18.3

29 kg N/ha - USG

10

4.2

3.4

26.9

58 kg N/ha - PU basal

9

4.1

3.4

12.2

58 kg N/ha - PU splits

10

4.2

3.4

13.6

58 kg N/ha - USG

11

4.5

3.4

19.1

Application of urea super granules at 10-12 days after planting at 8 cm depth was superior to the conventional best split application of prilled urea. Manual placement was effective when compared to application by applicator.

The need for an integrated nutrient management was demonstrated. This practice involving use of green manure (S. aculeata) supplying about 40 kg N/ha along with 40 kg N/ha supplied through inorganic fertilizer proved better than 80 kg N/ha supplied solely through inorganic fertilizer. Incorporation of fresh Azolla at 5 t/ha just before planting or its inoculation at 1 t/ha at planting and its incorporation after one month gave yields identical with application of 30 kg N/ha.

In a long-term experiment (12 years) to study NPK requirement of a long duration variety, Pankaj, no response was obtained to P and K application. Response to N was obtained up to 80 kg N/ha in the absence of compost application and up to 40 kg N/ha in presence of compost. Residual effect of compost persisted even up to the fourth year after the cessation of its application. When ammonium sulphate was applied in split doses to supply 75 kg N/ha, nitrogen was not lost through irrigation water where field to field irrigation was followed. On the other hand, when calcium ammonium nitrate was used to supply 50 kg N/ha, lateral movement of nitrogen took place.

Rice-fish-prawn seed system

Rice-fish seed farming besides providing additional income to the farmers, enhanced the grain yield of rice by around 10% with a marginal increase in straw yield.

Feasibility of insecticide use. Commonly used insecticides like carbofuran, phosphamidon, monocrotophos, quinalphos, and ethofenprox were found suitable at the recommended dose in rice-fish seed (fry to fingerlings production) system. However, these insecticides reduced the fish yield by 21 to 29% with one application and 47% with two applications by way of bringing down the plankton population by 25 to 50%.

Nutrient management through use of organics. Poultry droppings and farmyard manure were superior over water hyacinth and Azolla compost in rice-fish seed system. Growing of Azolla mat was not useful in this system particularly in terms of fish. Use of fish feed produced 50 to 100% more fish in the fields facilitated with pond refuge covering around 10% of the field area. Fish feed also accumulated significantly higher protein in fish flesh. Rice-fish seed farming provided a net additional income of Rs. 2000 to 3000/- per hectare within 2 to 3 months period.

Prawn seed culture. Production technology of freshwater giant prawn (Macrobrachium rosenbergii) seed raising with shallow lowland rice was developed at CRRI.

Intermediate and deep water situations

Varietal identification

Evaluation of promising cultivars from different sources revealed that for intermediate-deep water areas, semi-dwarf/tall photosensitive cultivars, CR 1010, CR 1016, Gayatri (CR 1018), Utkal Prabha (CR 1030), CR 260-77, CN 540 flowering during second fortnight of October were more suitable than traditional tall cultivars. Under semi-deep and deep water conditions, very tall cultivars (200 cm) like Jaladhi 1, Janaki, Nalini, Matangini, LPR 425 and Dinesh were more suitable than moderately tall (160-170 cm) cultivars.

Stand establishment.

Under intermediate-deep water condition, early direct seeding of semi-dwarf varieties was superior to transplanting, while the tall varieties performed better under transplanted condition. Aged seedlings of 45 days old were better than 30-day-old seedlings for transplanting. The seed density within the range of 400 seeds/m2 proved to be optimum. Early transplanting before July 10 increased the grain yield by more than two-fold as compared to delayed planting (last week of July).

It has also been demonstrated that as a contingency measure against complete damage of freshly planted crop in patches, transplanting with clonal tillers (double transplanting from 20 to 50 days in standing water depth of 50-60 cm) was superior to that of planting with aged seedlings obtained from available nurseries.

Mixed cropping of early and late maturing rice varieties

Sowing early maturing (85-95 days) and semi-tall (130 cm) upland rice varieties (Kalinga III or Vanaprabha) with the conventional late maturing (165 days) and semi-dwarf (110 cm) lowland varieties (Gayatri or Seema) in alternate lines 15 cm apart using 200 to 300 seeds/m2 of each variety, increased the overall grain yield by 15 to 20% over the sole crop yield of late variety.

Tillage and management of weeds

Treatment

Grain yield (t/ha)

Direct seeding
Control (no N)

2.5

40 kg N/ha through urea

3.3

Rice and dhaincha in 15 cm alternate rows

3.2

Rice and dhaincha in 20 cm in 2:1 ratio

3.0

Transplanting
Control (no N)

1.1

40 kg N/ha through urea

1.9

Planting after incorporation of pure daincha

2.1

CD (P= 0.05)

0.5

Off-season tillage in the month of January and/or summer ploughing in March with a tractor-drawn cultivator ensured a better crop stand of the direct-sown rice by providing fine tilth and early weed control than the conventional practice of ploughing just before sowing in mid-May. Further, the efficacy of pre-emergence herbicides, butachlor and thiobencarb applied at 2 kg/ha was also better in the well prepared field, ensuring near weed-free condition for the first 25-30 days of the crop growth.

Age of seedlings

Submergence for 10 days caused by flash flooding 30 days after transplanting was tolerated by the crop planted with 60-day-old seedlings than with 45 and 30-day-old seedlings. the crop planted with older and fertilized (100 kg N, 20 kg each of P2O5 and K2O/ha applied in the seed bed) seedlings established well in excess water and produced an yield of 3 to 4 t/ha.

Fertilizer management

In alluvial deltaic soils with average fertility, application of 30 to 40 kg N/ha was optimum with a ceiling at 60 kg N/ha. If the above moderate nitrogen application was coupled with good management, it was possible to achieve an yield of 4 t/ha.

Sub-surface application at sowing proved better than split application. For the transplanted crop, application of nitrogen in nursery at 100 kg N/ha helped the crop to tolerate submergence at late stage.

Green manuring with dhaincha

The feasibility of green manuring by growing rice and dhaincha (S. aculeata) simultaneously in different row arrangements was assessed. Dhaincha sown along with rice in alternate rows at a 15 cm spacing produced 2.8 t dry matter and supplied 67.5 kg N/ha compared with 3.4 t dry matter and 83 kg N/ha when grown in pure stand. Grain yield of direct-sown, green-manured rice was significantly more than that of the crop transplanted following incorporation of pure dhaincha, and was on par with the crop grown with 40 kg N/ha applied as urea fertilizer under both conditions.

Cropping system

By growing capsularis jute (JRC 7447) between May and September, followed by photosensitive late duration rice (CR 1014, T 141) planted in third week of September, it was possible to raise two crops during the wet season. This strategy could also be useful for flood-prone areas where time of occurrence and duration of flood is unpredictable during July-September. Possibility of growing sweet potato (85-16), greengram (Pusa 105), maize (Ganga 5), groundnut and sunflower under limited irrigated condition in the dry season after the harvest of long duration ricewas also demonstrated.