Two greenhouse experiments were conducted to study the Competition between redroot pigweed, broomrape, and potato. The first experiment was a replacement series in which potato and redroot pigweed were planted in different ratios, 4:0, 3:1, 2:2, 1:3 and 0:4, to determine Relative Crowding Coefficient (RCC). RYT> I showed that potato and redroot pigweed exploit the resources in different ways or somehow benefit each other. RCC of potato and redroot pigweed in 2:2 ratio was greater than in other ratios. This indicates that potato• is more aggressive than redroot pigweed. The second experiment was conducted to determine the effect of broomrape seeding rate on potato yield. The treatments consisted of 0, 20, 40, 6() and 80mg seed per pot, and were repeated three times in a randomized complete block design. Potato yield was reduced with increasing broomrape seeding rate. the least potato yield being obtained in pots with 60 and $0 mg broomrape seed.
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