Tests showed a soil to contain 25 kg nitrate-N per ha. About 2000 kg of wheat straw was applied to 1 ha of this land. The straw contained 0.4% N. How much N was applied in the straw? Explain why two...

Tests showed a soil to contain 25 kg nitrate-N per ha. About 2000 kg of wheat straw was applied to 1 ha of this land. The straw contained 0.4% N. How much N was applied in the straw? Explain why two weeks after the straw was applied, new tests showed no detectable nitrate N. Show your work and state what assumptions or estimates you made to do this calculation.