Passage III

Three studies examined the effects of compost (organic matter) on 3 physical properties of soil.

Five soil mixtures (Mixtures 1-5) were prepared (see Table 1).

Study 1

A 1.5 L pot was prepared by placing 500 g of Mixture 1 into the pot, after which the pot was stored at 30°C for 72 hr. The pot and its contents were then baked in a 105°C oven for 24 hr. After cooling, the mixture's bulk density (the dry mass of the mixture per unit volume) was determined.

These procedures were repeated for each of Mixtures 2-5 (see Table 2).

Study 2

Another 1. 5 L pot of Mixture 1 was prepared, stored, and baked as in Study 1.

The dried mixture was ground into powder and passed through a screen with 2 mm diameter openings. Five grams of the screened powder were then mixed with 5 mL of H2O. and the pH of the powder-H2O suspension was determined.

These procedures were repeated for each of Mixtures 2-5 (see Table 3).

Study 3

Another 1. 5 L pot of Mixture 1 was prepared, stored, and baked as in Study 1. The dried mixture was then ground and screened as in Study 2.

Fifty grams of the screened powder were mixed with 5 mL of H2O to form a soil paste, and the paste was placed on a filter. Suction was then applied to the filter. and the extract (the clear, colorless liquid that passed through the filter) was collected. The electrical conductivity of the extract was determined.

These procedures were repeated for each of Mixtures 2-5 (see Table 4).

19. Consider the statement "The percent by volume of compost in the mixture that had the greatest bulk density was the same as the percent by volume of compost in the mixture that had the extract with the lowest electrical conductivity." Do the results of Studies 1 and 3 support this statement?

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

Looking at Table 2, the maximum value of Bulk density is Mixture 5, and then looking at Table 4, the lowest value of Electrical conductivity is also Mixture5, and finally looking at Table 1, it is determined that the proportion of compost in Mixture 5 is 95%. Based on the above information, it is also Come up with answer B.