Based on observational data there are a few things considered to be conducive to male fertility:

Fitness. Higher fitness levels and less TV equate to higher sprem count and concentration.

Omega-3 Fats. Higher intake of omega-3 fats may increase male sperm health. Good sources include nuts (especially walnuts), chia and flax seeds and leafy greens.

Folate.  Higher folate intakes are correlated to better sperm quality. Good sources of folate are spinach and other dark leafy greens, nuts, beans, peas, eggs, dairy and grains.

Antioxidants.  Oxidative stress may account for up to 80% of male subfertility and the antidote is antioxidants! Increasing your intake of antioxidants can improve sperm quality and help couples get pregnant. 

Good sources include citrus, berries, tomatoes, colorful vegetables, nuts and cocoa.