Nitrogen

Nitrogen

1. assess SNS

   • comprises of...
     • SMN
       • Soil Mineral Nitrogen
         • can vary by 50% across a field
       • 15-20samples per 10ha
       • need to maintain field heat
         • get to lab asap
           • assure lab is accredited, worthwhile and specific
           • SMN increases during storage
             • 2.5kg/ha/day
         • keep cool if stored freezing increases SMN
     • N in crop
     • N mineralised from soil OM/crop debris
   • can predict from...
     • previous crop
       • potatoes high N sugar beet low
     • soil type
       • sands retain least N silts retain most
     • potential leaching
     • ALL PREDICTION
   • after ploughing out grass
     • releases a lot of N

2. allow for N in manures

   • urine/dung patches
     • causes hotspots

3. urea converts to ammonia

   • affected by heat and acidity
     • high pH

4. excess N causes lodging

5. SNS high in north west, SNS med in north east, SNS low in east

6. can sample in winter or spring

   • except...
     • light soils
     • shallow soils
     • high winter rainfall
   • 0-60cm in winter
     • less likely to overestimate
   • 0-90cm in spring
   • HGCA