Saturday, 23 July 2011

A Harvest Test to Verify Presence of Variability in a SRI-Rice Crop

Harvest Test

Salehuddin Yahya,
Principal, NS Nature Rice.

A harvest test based on a 15 meter crop strip was carried out during the harvest of SRI rice crop planted in Parit Empat Sungai Burong in State of Selangor in crop season April-July 2011.

Crop History
SRI rice was planted in a 0.34 ha test plot in Sungai Burong, Selangor. The crop was planted in a set of 4 rows 30 cm apart and 30 cm between plants within rows. Each set of rows is separated by 45 cm working paths. The plot was irrigated by pumping water from an adjacent drain. As with SRI-rice discipline, standing water was kept at soil surface level for 45 days. After 45 days field was to be kept inundated up to two weeks prior to harvest. Standing water, however, could only be supplied intermittently and not at all after 80 days. As a result the field suffered from premature drying.

The field was supplied with 1.5 ton of cow manure prior to start of season. No other fertilizer, except for a spray of a dose of foliar fertilizer by plot owner after 25 days of planting, was used. A combination of nature farming spray treatments developed by SRI farming enthusiasts for trial use in rice in State of Selangor was used as crop booster as well to ward off crop pests. Altogether six spray treatments were carried out.
Through out the growing period of the crop right through to time of harvest it had been observed that the crop performance vary markedly throughout the plot. The crop performed better at the western corner of the field. Soil fertility was seen to taper from good to low fertility in West-East direction of the field. The west corner of the field was the nearest corner to water source and had the bulk of the organic fertilizer incorporated within the soil in that corner too.

With the exception of attack from stem-borer, attacks from other pests and diseases were insignificant. Damage from stem-borer attacks, evidenced from presence of white-head inflorescence, was estimated at between 5% and 7%.

Objective of the harvest test
1. To verify extend of variability within plot
2. To ascertain potential maximum yield within plot

Waiting for harvest test cut
Delivery of yield from harvest test cut
Collecting yield from harvest test cut

A strip of crop 15 meter in width running East-West strip was identified and marked. Crop in plot was harvested leaving the crop in strip standing. Cuts of widths equivalent to 6 rows of rice were made across the 15-meter strip using the Iseki Mini Combine harvester. Each cut contains harvest yield from 300 hills. Altogether 9 cuts at pre-identified points along the length of the strip were made. Harvest yield from each cut was weighed.

Harvest yield from 9 cuts were (kg) ; 16.6; 14.2; 14.0; 15.4; 18.4; 15.0; 14.6; 18.2; 22.8.

Calculation of Potential Max Yield
Highest yield from strip harvest = 22.8 kg
Average output per hill = 22.8/300 = 0.076 kg
Total number of hills per ha = 98000
Estimated potential maximum yield from plot = 0.076 x 9800 = 7.45 ton per ha

Likewise a yield estimate from the 15 m strip can be deduced from average yield of the 9 cuts: 16.57 kg. Yield estimate from 15 m strip is 5.4 ton per ha

Actual Crop Yield From Plot
Total mill weight of harvest from the whole test plot was 1300 kg. Actual yield from the 0.34 ha test plot is therefore 3.82 ton per ha. It is to be noted that a significant portion of crop yield could not be accounted for due to factors such removal of mature plants for various analytical studies, removal of mature plants for displays at seminars and talks, as well as crop loss from harvester malfunction at the start of harvest.

  1. Crop performance variability within strip was very marked. There was a 40% difference in yield between the highest yield in strip harvest and the lowest yield
  2. Potential maximum yield for the crop is estimated at 7.45 ton per ha.

A high variability in crop performance existed within the test plot, as is evidenced from the estimated yield potential of 7.45 ton per ha as opposed to actual yield of 3.82 ton per ha. Even within the 15-meter strip picked for the harvest test an estimated 40% variability existed. The high variability was contributed, firstly, by plot not being level; and secondly, not having the organic fertilizer evenly distributed. It is imperative that potential variability within a rice field be minimized especially when planting rice using SRI method (*).

* Steps to be taken for next crop on same piece of land will be discussed in ensuing write-up.