Yoshida - 1981 - Fundamentals of Rice Crop Science

More documents

Recommendations

Info

PHYSIOLOGICAL ANALYSIS OF RICE YIELD 235 intensity. In a canopy with flat leaves the whole area of the top leaf is more exposed to sunlight than any lower leaf. But in a canopy with very erect leaves, the tips of lower leaves may receive more sunlight than the basal part of the flag leaf. 7.3. YIELD COMPONENT ANALYSIS 7.3.1. Relative importance of yield components The grain yield can be divided into several components (see Chapter 1). Equation (1.21) can be rewritten as: Y= N × W × F × 10 –5 . (7.2) where Y = grain yield (t/ha), N = spikelet number/m 2 , W = 1,000-grain weight (g), and F = filled spikelets (%). Each of the yield components differs not only in the time when it is determined but in its contribution to the grain yield. When IR747B2-6, an early-maturing variety, was grown throughout the year at Los Baños, Philippines, the grain yields of 19 crops ranged from 4.6 to 7.1 t/ha. To examine the relative importance of each yield component for grain yield in these crops, the percentage contribution was computed by means of correlation coefficients and multiple regressions based on a log scale (Equation 7.2 was converted to log Y = log N + log W + log F + R). While the combined yield components accounted for 81% of the yield variation, number of spikelets per square meter (N) alone explained 60% of the variation, and filled-spikelet percentages ( F ) and grain weight ( W ) together accounted for 219 (Table 7.2). If the contribution of all the yield components were taken as 100, which would have been true had there been no error in measurement, the contribution of number of spikelets per square meter would have been 74% and the combined contribution of filled-spkelet percentage and grain weight would have been 26%. Clearly, spikelet Table 7.2. Contribution of each yield component to grain yield. a Variable b Contribution to total variation in yield (%) N F and W N and F N and W N and F and W 60.2 21.2 75.7 78.5 81.4 a Yoshida and Parao (1976). b N = spikelet number per square meter; F = filled-spikelet percentage: W = 1,000-grain wt.
236 FUNDAMENTALS OF RICE CROP SCIENCE 7.3. Relationship between total number of spikelets per square meter. grain yield. filled-spikelet percentage, and grain weight of variety IR8 (Yoshida et al 1972). number per square meter was the most important component limiting yield in this experiment. A similar conclusion was obtained from IR8 crops grown at Los Baños (Fig. 7.3). The grain yield increased linearly with increasing spikelet number per square meter while filled-spikelet percentage and 1,000-grain weight remained fairly constant regardless of spikelet number. At some locations and in some weather conditions, filled-spikelet percentage may be more limiting to yield than spikelet number per square meter (Yoshida and Parao 1976). The 1,000-grain weight may affect yield to some extent but rarely becomes limiting under most conditions. Therefore, under given conditions it is important to examine the causes of yield variation in components, particularly spikelet number per square meter and filledspikelet percentage. 7.3.2. Spikelet number per unit land area Spikelet number per unit land area is affected by: • Cultural practices — spacing (seeding density) and nitrogen application. • Growth characteristics — tillering (seedling emergence). • Climatic conditions — solar radiation and temperature. Under subnormal cultural practices, the spikelet number per unit land area can be increased by increasing plant density and nitrogen application. Optimum spacing varies with tillering capacity and growth duration of a variety. A higher plant density is required for low-tillering, early-maturing varieties, and low nitrogen levels. The relationships between spikelet number per unit land area and amount of nitrogen absorbed by the crop have been discussed in Chapter 2 (Fig. 2.9).
Page 3 and 4:
FOREWORD Rice is vital to more than
Page 5 and 6:
CONTENTS Foreword Preface GROWTH AN
Page 7 and 8:
3.2. Adaptation to Submerged Soils
Page 9 and 10:
4.5. Corrective Measures for Nutrit
Page 11 and 12:
1 .1. OUTLINE OF THE LIFE HISTORY T
Page 13 and 14:
GROWTH AND DEVELOPMENT OF THE RICE
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
66 FUNDAMENTALS OF RICE CROP SCIENC
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
100 FUNDAMENTALS OF RICE CROP SCIEN
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194: 184 FUNDAMENTALS OF RICE CROP SCIEN
Page 203 and 204: 5.1. PHOTOSYNTHESIS 5.1.1. Photosyn
Page 205 and 206: PHOTOSYNTHESIS AND RESPIRATION 197
Page 207 and 208: Photosynthetic characteristics Meas
Page 223 and 224: A traditional tall variety vs an im
Page 243: 234 FUNDAMENTALS OF RICE CROP SCIEN
Page 257 and 258: Table 7.6. An example of high yield
Page 261 and 262: REFERENCES AGRICULTURAL POLICY STUD
show all

Yoshida - 1981 - Fundamentals of Rice Crop Science

Create successful ePaper yourself

Delete template?

Save as template?