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Crop-cut for Estimating B. Aus Rice Yield

Dr. Kamal Rahim
CSO and Head
Agricultural Statistics Division, BRRI, Gazipur

Manotosh Hawladar
PSO
Agricultural Statistics Division, BRRI, Gazipur

Abstract/ Executive Summary:

BR21 was broadcast in a big field. Care was taken during sowing so that seed were sown uniformly in the field fertilized with the recommended rate of fertilizers. The study was conducted to determine the optimum size and shape of crop-cut for estimating the yield 'of B. Aus rice. Coefficient of variation (CV) was used as a measure of precision for different crop-cut sizes and shapes. Smith's law was employed to relate CV (Y) and the cut size (X). The optimum crop-cut size (Xopt) was determined by the maximum curvature method. The shape of the crop-cut was determined under the constraint, Xopt = X10pt. X20pt where, X10pt = Number of basic units combined in north-south direction, and X20pt = Number of basic units combined in east west direction.For estimating the yield of broadcast Aus rice, the optimum size of crop cut is 6m2 and for the same cut size, the shape does not have any effect on the precision of the yield estimate. For conducting field experiments with broadcast Aus rice, the experimental plot should be at least 7 m² leaving the boarder areas for estimating yield.

Keywords: B Aus, Crop cut and Yield

Location:

Start Date: 01-07-1991

End Date: 30-06-1992

Program Area: Variety and Species

Non-commodity: Rice

Objectives:

The study was conducted to determine the optimum size and shape of crop-cut for estimating the yield 'of B. Aus rice.

Methodology:

BR21 was broadcast in a big field. Care was taken during sowing so that seed were sown uniformly in the field fertilized with the recommended rate of fertilizers. Timely weeding was not possible due to heavy rain, and only one weeding was done. As a result, the crop suffered from weed infestation. At the time of crop maturity, an area of 18- x 18-m was randomly selected from the field and divided into 324 basic units each of 1- x 1- m before harvest. Each unit was harvested, threshed, and grains weighed separately along with its moisture content. The harvests were adjusted at 14% moisture content. The number of hills was also counted for each basic unit. The different cut sizes and shapes were generated by combining the adjacent basic units. Coefficient of variation (CV) was used as a measure of precision for different crop-cut sizes and shapes. Smith's law was employed to relate CV (Y) and the cut size (X). The optimum crop-cut size (Xopt) was determined by the maximum curvature method. The shape of the crop-cut was determined under the constraint, Xopt = X10pt. X20pt where, X10pt = Number of basic units combined in north-south direction, and X20pt = Number of basic units combined in east west direction.

Source of Information: BRRI Annual Report 1992, 188-189, BRRI, Gazipur.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Results indicate that the cut shape should be 2.58 m long and 1.53 m wide for estimating yield. On the other hand, the cut shape for estimating hills should be 2.45 m long and 1.77 m wide from the same field. It is difficult to take different cut sizes and shapes for estimating different characters from the same field. So, a compromise seems to be necessary to take a single cut size and shape for estimating both the characters. To avoid any risk in estimating the characters under study, the cut shape seems to be justified and adequate as 3 m long and 2 m wide. The contour maps for yield (gm/m²) and hills (no. 1m²) revealed that they were not uniform, rather patchy over the field. The fertility gradient was along the north-south direction. Results indicate that the length of the cut should be 3 m along the fertility gradient and the breadth should be 2 m along the perpendicular line.

The following conclusion was drawn:

• The optimum size of crop-cut for estimating the yield and the number of hills seems to be adequate and justified as 6 m².

• The shape of crop-cut should be rectangular where length should be elongated along the fertility gradient and the breadth as the perpendicular to it, and it should be 3- x 2-m.

Knowledge Management: Report/Proceedings