Yampracha, Sukunya

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Yampracha, Sukunya
Alternative Name
Yampracha, S.
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Email
sukunya.ya@kmitl.ac.th

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    Nitrogen requirements of cassava in selected soils of Thailand
    (2013-08-20)
    Kaweewong, Jakchaiwat
    ;
    Kongkeawa, Thanuchai
    ;
    Tawornprek, Saowanuch
    ;
    Yampracha, Sukunya
    ;
    Yost, Russell
    Cassava (Manihot esculenta) is one of the most important export crops in Thailand, yet the nitrogen requirement is unknown and not considered by growers and producers. Cassava requirements for N were determined in field experiments during a period of four years and four sites on the Satuk (Suk), Don Chedi (Dc), Pak Chong (Pc), and Ban Beung (BBg) soil series in Lopburi, Supanburi, Nakhon Ratchasima, and Chonburi sites, respectively. The fertilizer treatment structure comprised 0, 62.5, 125, 187.5, 250 and 312.5 kgNha <sup>-1</sup> as urea. At each site cassava was harvested at nine months and yield parameters and the minimum datasets were taken. The fertilizer rate which resulted in maximum yield ranged from 187.5 kgNha <sup>-1</sup> in Supanburi and Chonburi (fresh weight yield of 47,500 and 30,000 kg ha<sup>-1</sup> respectively) to 250 kgNha<sup>-1</sup> in Lopburi and Nakhon Ratchasima (fresh weight yield of 64,100 and 46,700 kg ha<sup>-1</sup> respectively). Yield appeared to decrease at the higher, 312 kg ha <sup>-1</sup>, at Supanburi and Lopburi, and 250 kg ha<sup>-1</sup> (Chonburi) fertilizer N rates. Net revenue was 70.4 and 72.9% higher than where no N was applied at Lopburi and Nakhon Ratchasima sites. Net revenue at the Supanburi and Chonburi sites were 53.8 and 211.0% higher than that where no N was applied. This study suggests that at all sites improved cassava production and net revenue could be obtained with the judicious application of higher quantities of N. The results provide needed guidance to nitrogen fertilization of the important industrial crop cassava in Thailand.
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    Phosphorus-Sorption Characteristics and Phosphorus Buffer Coefficients of Some Important Soils in Lao PDR
    (2015-03-09)
    Souliyavongsa, Xaysathid
    ;
    Yampracha, Sukunya
    ;
    Attanandana, Tasnee
    ;
    Yost, Russell
    ;
    Kanghae, Piboon
    An estimated 97 percent of the soils in Laos are characterized by low phosphorus (P). This characteristic, together with high acidity, constrains food crop production. The P status, sorption, and associated properties were evaluated for fifteen important agricultural soils from the uplands. Soil pH values ranged from 4.5 to 5.9. Soil organic carbon (C) varied from 7.0 to 22.9 g kg<sup>−1</sup>. Soil clay varied from 179 to 709 g kg<sup>−1</sup>. The cation exchange capacity (CEC) also varied from 4.30 to 32.1 cmol<inf>c</inf> kg<sup>−1</sup>. Extractable P levels of thirteen of the fifteen soils were P deficient with medium to very high P sorption, indicating substantial fertilizer P requirements. Dithionite and oxalate aluminum and iron predicted P sorbed at 0.2 mg P L<sup>−1</sup>. The extractable P increase per unit added P, P buffer coefficient (PBC), was low, also indicating high P sorption. Field studies are needed to confirm predictions of P requirements.
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    Cassava nitrogen requirements in thailand and crop simulation model predictions
    (2013-05-01)
    Kaweewong, Jakchaiwat
    ;
    Tawornpruek, Saowanuch
    ;
    Yampracha, Sukunya
    ;
    Yost, Russell
    ;
    Kongton, Sahaschai
    While cassava is an important crop in diverse regions of Thailand, little information is available to compare sites, select planting dates, and determine nitrogen (N) requirements. In recent years, the Decision Support System for Agrotechnology Transfer (DSSAT) has been used to develop this information. In order to use DSSAT, the cassava model, namely, CSM-CSCRP-Cassava, needs to be calibrated and validated. A cassava response to nitrogen study was conducted in Thailand during the 2011-2012 growing season. The data were also utilized to calibrate the DSSAT cassava model on cultivar Kasetsart 50. The model could be calibrated to predict the first branching date at 116 days, when it actually occurred at 117 days after planting. The overall average top dry weight and dry root yield were 7.39 and 15.69 t [BULLET OPERATOR] ha, which were predicted with a root mean square error of 0.496 and 0.702, respectively. Maximum leaf area index, leaf N (%), and harvested root N (%) were also adequately simulated. Validation experiments were conducted at the diverse Lopburi, Supanburi, and Chonburi sites. Top dry weight and dry root yield were predicted with indexes of agreement of 0.86 and 0.95 in Lopburi, 0.82 and 0.95 in Supanburi, and 0.83 and 0.55 in Chonburi. Nitrogen requirements for maximum yield were overpredicted by the model, indicating additional work is needed to account for negative effects of excessive N. Effects of regional weather conditions and soil types appeared to be adequately predicted by the calibrated model. Improved planting dates were suggested with the calibrated model. Copyright © 2013 by Lippincott Williams & Wilkins.