Evaluation of varietal purity of certified basmati 370 and bw 196 from two rice seed sources in mwea and the response of rice to varying n, p and k fertilizer regimes
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Cultivating good quality seed and using appropriate nutrient levels are critical in reducing the current rice yield gap (8.5 t/ha) in kenya. Planting good quality seed reduces the susceptibility of crops to diseases, improves response to management, results in uniform crop maturity and increases grain yield. Using suitable fertilizer regimes can increase rice crop yields by up to 70%. Currently, the genetic purity of variety basmati 370 and bw 196 rice sourced from the national irrigation board (nib) and mwea rice growers multipurpose (mrgm) is unknown. The response of the two varieties to varying fertilizer regimes has not been determined. The objectives of this study were: 1. To determine the genetic purity of two rice varieties obtained from different seed sources in mwea and 2. To determine the response of selected paddy rice varieties to varying levels of inorganic fertilizers. Field experiments were set up between august 2016 and january 2017 and between august 2017 and january 2018, at miad, mwea division, kirinyaga county. A sample size of 30 plants was taken per treatment. In the first objective, 40 agro-morphological rice characteristics were examined based on upov standards of evaluation. In the second objective, a randomized complete block design, was laid-out in split-plots having 13 n kg/ha: p2o5 kg/ha: k2o kg/ha fertilizer ratios as the main plots and two rice varieties (basmati 370 and bw 196) as the sub-plots. The 13 n, p and k fertilizer regimes were as follows: 00:00:00, 60:40:40, 80:60:60, 100:80:80, 60:40:00, 80:60:00, 100:80:00, 60:00:40, 80:00:60, 100:00:80, 00:40:40, 00:60:60 and 00:80:80. The presence of anthocyanin pigmentation, shape of the ligule, the coloration of stigma, lemma, basal leaf sheath and ligule, did not show any variation for both seasons for plants generated from nuclear, mrgm and nib seeds, of variety bw 196 and basmati 370. Variety basmati 370 plants generated from nib seed exhibited a diversity index (0.14) which is higher than that of nuclear and mrgm (0.00) seeds. Variety bw 196 expressed higher diversities than variety basmati 370. Plants generated from the nuclear seed had the highest diversity index in the first (0.17) and in the Second (0.25) season. Except for leaf blade width in the first season, all the quantitative traits studied revealed insignificant differences (p≤0.05). Variety bw 196 from nib had significantly wider blades than those from mrgm. Variety basmati 370 seeds exhibited less genetic diversity than bw 196. Variety bw 196 had more than four off-types in 1500 hundred plants, rendering the seed impure when checked against the upov’s, dus test guidelines. Fertilizer application significantly (p≤0.05) increased plant height, number of tillers per hill, panicle length and grain yield, but had no significant (p≤0.05) effect on the one thousand grain weight. Fertilizer regimes 100:00:80 and 100:80:00 delayed heading and maturity only in the second season. The highest yields were recorded in 80:60:60, 80:00:60, 100:80:80 and 100:00:80 in both seasons. The study has demonstrated that unlike variety basmati 370, bw 196 was not genetically pure. Further, fertilizer regimes containing n and k elicited higher responses than fertilizer regime containing p. The highest yielding and most cost-effective fertilizer regime for rice production in mwea is 80:00:60.
University of Nairobi
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