The effect of spacing, fertilizer rate and method of fertilizer placement on the yield and yield components of two potato (Solanum Tuberosum L.) varieties: Annett and B53
This thesis reports on experimental work carried out on Irish Potato (Solanum Tuberosum ; over two seasons: 1976 - 79 short rains (SEASON I) and 1979 long rains (SEASON II), at Kabete Faculty of Agriculture Field Station located 1° 1A ' S and 3G AA' E., with an altitude of lQSQm above sea-level. The average annual rainfall for Kabete is 925 mm. In the tuo seasons of the experiment, the rainfall recorded uas A08 and 590 mm respectively. In the second season a continuous dry spell necessitated one sprinkler irrigation of 30.0 mm in the ninth week after 50% emergence. The main objectives of the two experiments were: 1. To test feasibility of using different plant populations for ware and for seed tuber production. 2. To test the possibility of improving on fertilizer use by using hill placement. 3. To test the performance of three fertilizer rates. A. To monitor some growth parameters and relate them to the final yield. The importance of the potato in Kenya, the scope for improvement and the problems encountered in potato production have been given. Both experiments were factorials laid out in Randomized Block Design. Experiment I (VarietyX Plant Population x Fertilizer rates) had two varieties: Annett and B53; three spacings: 75 x 2D cm, 75 x 25 cm, 75 x 30 cm and three fertilizer rates: 3AA, A30 and *^L7 kg DAP (diammoniumphosphate)/ha• Experiment II (Variety x Method of fertilizer placement\ x Fertilizer rates) had two varieties: Mnnett and B53, two methods of placement: hill placement and broadcasting in the furrow; and four fertilizer rates: □, 3AA,A30 and 517 Kg. DAP/ha., Annett was found to yield more than B53. Annett gave more of its yield as ware than B53 which gave more yield in the seed grades. Annett developed peak leaf area very quickly but maintained it for shorter periods than B53 which had a longer leaf area duration attained peak leaf area much later. but Hill placement of fertilizer attained higher total tuber yield than broadcasting in the furrow. The three fertilizer levels tested significantly outyielded the control bgt they did not significantly differ. However, it was found that the recommended 517 Kg. DAP/ha was in excess of the most ideal fertilizer rate for Kabete conditions. Raising plant population above 44444 to 66666 plants/ha did not significantly increase total tuber yields but the proportion of seed tubers increased as the plant(hill) density increased. Therefore, for seed production plant populations above 44444 plants/ha for Annett and B53 are batter. From the results of this work, the following suggestions for further experimentation are made 1. A broader fertilizer rates experiment to determine the most efficient rate for Kabete. 2. To test the economics of using plant populations higher than 4444 plants/ha for seed production, when the actual total tuber yields does not significantly increase. 3. To monitor fertilizer rates at which scorching begins when fertilizer is hill pieced.