What effect does plant residue and mulch on the soil surface have on the infiltration rate?

Correct answer: It protects soil structure and increases infiltration rate

Answer: B. Infiltration is the entry of water from the ground surface into the soil. Plant residues and mulch absorb some of the raindrop impact, so the impact is less likely to break soil aggregates and seal the surface with fine particles. Organic cover also helps maintain a porous structure, slows surface flow, and gives water more time to enter the soil. Therefore infiltration usually increases, while direct runoff may decrease. A is wrong because mulch does not form an impermeable barrier; water can pass through or around it. C is wrong because protecting the surface and slowing flow generally reduces, rather than greatly increases, runoff. D is wrong because mulch often reduces direct evaporation and helps conserve moisture. The exact effect depends on soil type, slope, rainfall intensity, and the amount of cover, but B is the correct general relationship. Memory cue: mulch cushions rain and keeps soil pores open.