Pak. J. Weed Sci. Res. 9(1-2):59-65, 2003

IMPACT OF SEEDING DATES AND VARIETIES ON WEED INFESTATION,
YIELD AND YIELD COMPONENTS OF RICE  (ORYZA SATIVA L.)

UNDER DIRECT WET-SEEDED CULTURE¹

Khizar Hayat1, Inayat Ullah Awan¹ and Gul Hassan2

ABSTRACT

                To study the effect of different seeding dates and varieties on the yield and yield components of rice under direct wet-seeded rice culture, an experiment was conducted at Agricultural Research Institute D.I.Khan, NWFP, Pakistan, during 1999 and 2000. Mean values of the data indicated that different varieties had significant effect on dry weed biomass (g m^-2), panicle m^-2, and spikelets panicle^-1 during both the years of the study. Varieties affected the sterility percentage, 1000-grain weight (g), paddy and straw yield (t ha^-1) during 1999 only. While seeding dates affected all the above mentioned parameters as well as harvest index during 1999 and 2000.

Key words: Rice, Oryza sativa L., weeds, direct wet seeding, seeding dates, varieties.

INTRODUCTION

Rice (Oryza sativa L.) is the most important food crop of the world. It has been the primary staple food for millions of people, for centuries. Rice is also the main livelihood of rural population in many Asian, African and Latin American countries (Labrada, 1998). Similarly, it is true for Pakistan as well, where it is next to wheat in this respect. In Pakistan, rice is cultivated on an area of 2.52 million hectares with a production of 5.16 million tones annually having an average yield of 2050 kg ha^-1 (Anonymous, 2000). The importance of rice for our country is manifold, as it is an agricultural commodity that adds 20 % of the total foreign exchange to the national foreign exchange reserves (Anonymous, 2001). Though, the yield of rice per hectare in Pakistan has increased from 970 kg to 2050 kg ha^-1 during 1999-2000 due to the introduction of high yielding IRRI rice varieties. But, still it is well below the world’s average. Rice is either planted by transplanting or direct seeding methods. The transplanting however, involves costly labor, uneven planting, lesser density per unit area, compaction of soil structure due to puddling and failure of nursery due to various factors i.e. unfavorable weather conditions, nutrient deficiencies and toxicities (Sohail et al., 1999). Moreover, nursery raising in transplanted rice means engaging the field for nearly a month earlier to transplanting that requires additional expenditure and intensive care unlike direct seeding. Due to these reasons, most of the farmers are no more in favor of raising rice crop through transplanting that has made shift unavoidable from transplanting to direct seeded culture. Most of the field experiments and on-farm research have proved accurate seed rate, timely seeding, efficient weed control and water management under direct seeded conditions giving as high yield as transplanted rice with comparatively lower production cost (Awan et al 1989 and Baloch, 1994).  In some experiments even higher than transplanted rice (Shad, 1983). Weeds are the main hurdle in adopting direct seeding culture. Different cultural measures could be easier and cheaper ways to minimize weed population. Delayed seeding after a heavy rain and a dry period has been advocated by Vongsaroj (1998) for reduction of weed problem, while Puckridge et al (1987) observed reduction in wild rice population by delaying seeding of rice from May to June. Keeping in view the importance of direct seeded culture, studies were undertaken to investigate the proper time combined with the adaptable variety for raising rice crop through direct seeding to realize optimum yields with lower input costs.

MATERIALS AND METHODS

A field experiment to study the yield and yield components and weed population as affected by different seeding dates and varieties of rice under direct wet seeded culture, was conducted during 1999 and 2000 at Agricultural Research Institute D. I. Khan, NWFP, Pakistan. During first year of the trial, the preceding crop was Brassica napus and during second year the experiment followed the wheat crop. Split-plot arrangements were used in Randomized Complete Block Design with three replications. Sub-plot size measured 5 x 3 m². Varieties (IR-6, IR-9 and KS-282) were allotted to main plots, while seeding dates were kept in the sub-plots. The first seeding was done on May 9, while the subsequent seedings were done at 10 days interval upto June 18, during the consecutive years of studies. Pre-germinated seed @ 100 kg ha^-1 was broadcast in the moist plots. Weed density and biomass were taken using 0.25 x 0.25 m² quadrate randomly from 3 sites in each sub-plot 45 days after seeding, subsequently oven-drying at 80⁰C for 48 hours. Data recorded on weed density and dry weed biomass subsequently converted to number of weeds m^-2 and g m^-2, respectively. The other data recorded were number of panicles m^-2, spikelets panicle^-1, sterility percentage, 1000-grain weight (g), straw and paddy yield (t ha^-1) and harvest index. The data thus collected were subjected to analysis of variance technique appropriate for the design. The significant means were separated by Duncan’s Multiple Range Test  (Steel and Torrie, 1984).

RESULTS AND DISCUSSION

Dry weed biomass (g m^-2)

The data recorded for the parameter (Table-1) revealed that D₅ (June 18) seeding gave the lowest while, D₁ (May 9) produced significantly highest weight of dry weed biomass (g m^-2) during both the years. However, during 1999, D₁ was at par with D₂ and D₃, while during 2000, D₅ did not differ from D₄, and D₂ was at par with D₃ for the trait, statistically. Variety KS-282 produced the lower dry weed biomass during 1999 and 2000, though during second year KS-282 and IR-9 were at par statistically for the dry weed biomass. This might have been due to the difference in the soil fertility under the experiments during the trial years and difference in the weed flora.

Table 1.   Dry weed biomass (g m^-2) as affected by different seeding dates and varieties in direct wet seeded rice culture during 1999 and 2000.

Means followed by the same letter (s) are non-significant by DMRT at 5 % level of probability.

Number of panicles m^-2 in rice

Data recorded on the number of panicles m^-2 (Table-2) showed that more number of panicles were observed when seeding was done on June 18 (D₅) and the minimum number of panicles were recorded in D₁ (May 9) seeding during both the years. Though during 1999, D₁ did not differ from D₂ and D₃ while, D₅ was at par with D₄ statistically, for the parameter under reference. IR-6 gave the maximum number of panicles during both the years. However, during first year of the trial IR-6 was at par with KS-282 for the trait. The results agree with those reported by Awan (1988) and Gandapore (1999). The former researcher observed non significant difference between the number of panicles produced by IR-6 and KS-282, while the later observed significant difference between the number of panicles of IR-6 and IR-9 varieties of rice.

Table 2. Number of panicles (m^-2) as affected by different seeding dates and varieties in           direct wet seeded rice culture during 1999 and 2000.

Means followed by the same letter (s) are non-significant by DMRT at 5 % level of probability.

Number of spikelets panicle^-1

The data indicated (Table-3) that D₅ (June 18) seeding gave more number of spikelets per panicle than early seeding during both the years. However, during 1999, D₁, D₂ and D₃ were at par, while D₄ and D₅ did not differ from each other for the number of spikelets. During 2000, D₁ and D₂ were at par statistically for the trait. KS-282 produced more spikelets during both the years. However, during 1999, KS-282 was at par with IR-6 and during 2000, IR-6 and IR-9 did not differ from each other for number of spikelets per panicle. This may be due to the difference in the mean temperatures, humidity, the soil and the weed flora in either year of  the trial. The results agree with the findings of Hassan et al., (1999) and Awan et al., (2001) who observed that KS-282 produced significantly higher number of spikelets than variety IR-6, though statistically at par but numerically higher than those produced by IR-9.

Table 3. Number of spikelets panicle^-1 as affected by different seeding dates and varieties in direct wet seeded rice culture during 1999 and 2000.

Sterility percentage

Similar trend of sterility percentage was observed during both the years (Table-4). Minimum sterility was observed in D₅ (June 18) seeding, while D₁ (May 9) seeding gave the maximum sterile spikelets during both the years of studies. However, first three seeding dates were at par with one another statistically and D₄ and D₅ also did not differ from each other for sterility percentage during both the years. KS-282 produced minimum sterility percentage during both the years. IR-6 and IR-9 did not differ from each other statistically, during 1999, whereas during 2000, all the varieties were at par with one another for the parameter under study. Comparatively, higher sterility percentage during the second year may be due to the difference in the mean temperature and humidity during the two seasons. The results are in accordance with the findings of Javed et al., (1979), Awan (1988), Hassan et al., (1999) and Awan et al., (2001).

Table 4. Sterility percentage as affected by different seeding dates and varieties in direct                  

                wet seeded rice culture during 1999 and 2000.

Means followed by the same letter(s) are non-significant by DMRT at 5 % level of probability.

1000-grain weight (g)

The data in Table-5 reveal that D₅ (June 18) seeding had significantly heavier grains than all the early seeding dates during both the years of the trial. However, D₁, D₂ and D₃ were at par for grain weight during both the years, while D₅ did not differ from D₄ for the trait during 2000. KS-282 gave higher weight for 1000-grains during both the years; however, during second year this variety was different statistically from IR-6 and IR-9. These findings agree with the work reported  by Awan (1988) and Hassan et al., (1999).   

Table 5.  1000-grain weight (g) as affected by different seeding dates and varieties in direct   wet seeded rice culture during 1999 and 2000.

Means followed by the same letter (s) are non-significant by DMRT at 5 % level of probability. 

Paddy yield (t ha^-1)

D₅ (June 18) seeding produced significantly higher paddy yield than all the seeding dates, however, it was statistically at par with D₄ during both the years (Table-6). The first three seeding dates also did not differ from each other for the paddy yield during both the years of the trial. KS-282 produced maximum yield (7.6 t ha^-1) during 1999, but was statistically at par with IR-6 (6.8 t ha^-1). Similarly, KS-282 produced higher yield (7.06 t ha^-1) numerically, but did not differ from those given by IR-6 and IR-9 during 2000. Comparatively, higher paddy yield obtained during 1999 than 2000 could be attributed to lower sterility percentage and dry weed biomass as well as higher weight of 1000-grain during 1999 experimentation. The results are in accordance with those of Awan (1988), Pande and Gautum (1988) and Hassan et al., (1999).

Table 6.   Paddy yield (t ha^-1) as affected by different seeding dates and varieties in direct wet seeded rice culture during 1999 and 2000.

Means followed by the same letter (s) are non-significant by DMRT at 5 % level of probability.

Straw yield (t ha^-1)

The data in Table-7 revealed that D₄ and D₅ were at par with each other for straw yield but significantly higher than the remaining three dates during both the years. KS-282 gave significantly higher straw yield during 1999 but was at par with IR-6 and IR-9 during 2000. Higher straw yield during 1999 than that during 2000 may be due to more plant height because of different soil fertility levels between the trial years. Similar, results were reported by Hassan et al., (1999) and Awan et al., (2001).

Table 7. Straw yield (t ha^-1) as affected by different seeding dates and varieties in direct wet seeded rice culture during 1999 and 2000.

Means followed by the same letter (s) are non-significant by DMRT at 5 % level of probability.

Harvest Index

Similar trend of harvest index was observed during both the years (Table-8). D₄ and D₅ were at par with each other but significantly higher than D₁, D₂ and D₃ for harvest index during both the trial years. The varieties did not differ from one another during both the years. The results agree with those reported by Awan (1988) and Awan et al., (2001).

Table 8. Harvest index as affected by different seeding dates and varieties in direct wet  seeded rice culture during 1999 and 2000. 

Means followed by the same letter (s) are non-significant by DMRT at 5 % level of probability.

CONCLUSION

It is concluded from the two year studies that no systematic trend was observed for the yield and yield components when direct seeding was done on May 9, 19 and 29 while, seeding on 8^th and 18^th of June affected the yield parameters significantly and also produced lower dry weed biomass. KS-282 variety of rice planted during second week of June produced the highest paddy yield (t ha^-1).                           

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