Questions 21-27 are based on the following passage.
Two studies were done to examine how the proportion of vermicomposr (feces from earthworms) in a particular potting soil affects the yield of each of 2 plant species: Solanum lycopersicwn (a tomato plant) and Capsicum annuum (a pepper plant). The yield of a plant species is the
mass of fruit produced per plant of the species.
Six different mixtures (Mixtures 1-6) were prepared according to the percents listed in Table 1.
Study 1 Equal amounts of Mixtures 1-6 were distributed among thirty-six 2 L pots in the foJJowing manner: 1.5 kg of Mixture 1 was put into each of 6 pots, 1.5 kg of Mixture 2 was put into each of 6 other pots, 1.5 kg of Mixture 3 was put into each of 6 other pots, and so on. Theo, 3 S. lycopersicum seeds were added to each pot. For the next 158 days, all the pots received equal amounts of water and light. On Day 28 of the 158 days, all the seedlings that had emerged were removed from the pots with the excep tion of a single seedling in each pot. On Day 158, the yield of the remaining plant in each pot was measured. The average yield of the plants grown in each mixture was then calculated. The results are shown in Figure 1.
Study 2 The procedures of Study l were repeated, except that 5 C. annuum seeds instead of 3 S. lycopersicum seeds were added to each pot, the pots received water and light for 149 days instead of 158 days, seedling removal occurred on Day 42 of the 149 days, and plant yield was measured on Day 149. The results are shown in Figure 2.