ABSTRACT

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during the period from 25 November 2005 to 13 April 2006 to study the effect of detillering and row spacing on growth, yield and yield attributes of BRRI dhan28. The experiment consisted of four detillering treatments viz., 6 tillers kept hill-1 (T₁), 9 tillers kept hill-1 (T2), 12 tillers kept hill-1 (T3) and intact hills (T4) and four row spacing were 25 cm x 15 cm (S₁), 20 cm x 15 cm (S2), 15 cm x 15 cm (S3) and 10 cm x 15 cm (S4). The experiment was laid out in a randomized complete block design with three replications. The effect of detillering was found to be significant in all the characters under study except 1000-grain weight. The plant height, panicle length, number of grains panicle’, grain yield and straw yield were observed statistically significant and also found identical both in the case of 9 and 12 tillers kept hill-1. The maximum number of effective tillers (10.04) was found in 12 tillers kept hill-1 than that of other treatments. The spacing 20 cm x 15 cm showed better performance in general, although most the parameters were statistically similar with that of spacing 25 cm x 15 cm. The highest grain yield of 5.04 t ha-1 was recorded in case of 20 cm x   15 cm spacing. Interaction effects between detillering and row spacing were significant for most of the growth characters and yield components under study except 1000-grain weight. The treatments 9 tillers kept hill spaced with 20 cm x 15 cm and 12 tillers kept hill-1 with the same spacing were found to be significantly superior in the case of number of grains panicle’, grain yield and straw yield, although they were found identical with some other interaction treatments under the same parameters. The detillering with retaining of 9 tillers hill-1 at 20 cm x 15 cm spacing was the best possible combination for achieving optimum grain yield of BRRI dhan28.

Key words: Detillering, spacing, BRRI dhan28.

Introduction

 The rapid population growth is continuously diminishing the productive rice areas from the existing 10.27 million hectares (BBS, 1997). Moreover, Bangladesh is in continual annual shortage of about 1.5 million tons of food grains (Karim, 1999), and this shortage will be severe if the present level of population growth continues. Recent projection shows that rice demand in Bangladesh will reach over 40 million tons in 2020. Rice yield may be influenced by such factors as row and plant spacing and number of tillers hill-1. Improper spacing and tillers hill-1 may affect the physiological activities of rice plant and account for yield reduction to a great extent. Row spacing and number of tillers hill-1are the key factors that determine the availability of sunlight, nutrient, water and the rate of photosynthesis and ultimately the yield. To enhance this physiological process of growth tiller separation is sometimes practiced in Bangladesh (Hossain et al., 1988), especially in post flood situation. So, it is important to know the performance of BRRI dhan28 as a boro rice as affected by detillering from which information about optimum number of tillers hill-1 can be determined for having better growth and development of mother plant. On the other hand, distance between row to row is also an important factor that needs to be considered during cultivation of BRRI dhan28 as a boro rice crop. In case of closer spacing, more competition arises among the plants for nutrient, air and light as a result plants become weaker and thinner and reduction of yield occurs. In wider row spacing, farmers may not get desired number of hills which also ultimately may reduce yield per unit area. Thus proper row spacing ensures optimum plant population which allows the plants to grow properly after even detillering both in their aerial and underground parts resulting in efficient utilization of solar radiation and nutrients (Miah et al.,1990). That is why, it may be important to know the effect of row spacing and the number of tillers hill-1 on the growth and yield of BRRI dhan28 after detillering from the mother plant. The

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