A certified organic grower plans to grow a crop that requires the application of 120 kg of plant-available N/ha and 20 kg/ha at P. She has a source of compost that contains 1.5% total N (with 10% of this available in the first year) and 1.1% total P (with 80% of this available in the first year),

(a) Assuming her soil has a low P soil test level, how much compost should she apply to provide the needed N and P?

(b) If her soil is already optimal in P, how can she provide the needed amounts of both N and P without causing further P buildup?