Desarrollo actividad: Definir las especificaciones y/o requisitos del prototipo

Data  from  a  total  of  six  studies  went  into  determining  the  impact  on  nitrate  and  corn  yield.  Current   thoughts  of  the  nitrogen  science  team  are  that  the  price  variability  in  nitrogen  in  recent  years  has  limited   the  cost  difference  between  fall  and  spring  application,  therefore,  the  same  fertilizer  nitrogen  cost  is  used   for  all  timing  comparisons.  There  will  be  a  possible  economic  gain  due  to  increased  yields  with  a  change  in   application  timing.  

(Randall  and  Sawyer,  2008)  

Interpretation  section  –  “Spring  application  of  N  is  superior  to  fall  application  in  most  cases.”    The  

advantages  are  limited,  however,  to  warm  and  wet  conditions.  Authors  suggest  losses  of  fall  applied  N  may   be  as  much  as  50%  under  perfect  denitrification  conditions.  Reductions  of  N  loss  due  to  leaching  are   estimated  to  be  around  15%  with  as  little  as  no  reduction  and  as  much  as  25%,  depending  on  application   timing  and  weather  conditions.  Applying  in  spring  could  cost  between  $5  and  $10  per  acre  more.  However,   this  could  be  a  wash  if  more  is  applied  in  the  fall  to  offset  expected  losses.  Authors  suggest  an  estimated   12.9  million  acres  out  of  50.6  million  acres  in  the  Corn  Belt  could  benefit.  This  paper  was  not  used  in  the   practice  table  but  was  used  to  guide  estimates  of  fall  nitrogen  application.  

(Randall  and  Mulla,  2001)  

This  paper  reports  an  average  of  20%  load  reduction  at  Waseca,  Minnesota  (1987-­‐1993)  when  comparing   fall  vs.  spring  nitrogen  application  over  a  4-­‐year  period.  The  addition  of  nitrapyrin  reduced  nitrate-­‐N   concentrations  by  15%.  The  split  application  (pre-­‐plant  along  with  sidedress  in  a  40%-­‐60%  split)  also  

reduced  annual  nitrate-­‐N  concentrations  from  tile  lines  by  20%  over  the  same  4-­‐year  period.  This  study  also   included  information  about  nitrate-­‐N  concentrations  from  different  cropping  systems,  which  was  the  same   as  information  in  (Randall  et  al.,  1997).  Data  from  this  paper  was  not  included  in  the  practice  table.  

(Randall,  2008)  

This  paper  has  nitrate  concentration  numbers  for  both  fall  and  spring  applications,  however,  all  fall   applications  used  N-­‐Serve,  meaning  there  is  no  real  control  treatment  to  compare  against.  A  point  of   interest  is  the  fall  135  kg  N/ha  (120  lb  N/acre)  treatment  with  N-­‐Serve  and  the  spring  135  kg  N/ha  (120  lb   N/acre)  treatment  have  weighted  nitrate-­‐N  concentrations  of  13.2  and  13.7  mg/L,  respectively.  Corn  yields   for  the  fall  120  lb  N/acre  treatment  with  N-­‐Serve  were  0.9  Mg/ha  (14  bu/acre)  higher  than  the  

corresponding  spring  application.  Data  for  yield  and  nitrate  was  added  to  the  table  for  timing,  inhibitor,  and   sidedress.  

(Vetsch  and  Randall,  2004)  

This  paper  has  limited  data  for  use  in  this  project.  Fall  corn  yields  for  grain  and  silage  were  10.9  and  16.8   Mg/ha,  respectively,  while  spring  yields  for  corn  were  11.7  and  17.6  Mg/ha  for  grain  and  silage,  

respectively.  Anhydrous  ammonia  at  123  kg  N/ha  was  applied  to  both  spring  and  fall  treatments.  Data  was   not  included  in  the  practice  table.  

(Randall  and  Vetsch,  2005c)  

This  6-­‐year  study  from  Waseca,  Minn.,  has  information  about  nitrogen  application  timing  as  well  as  the  use   of  a  nitrification  inhibitor  with  a  134  kg  N/ha  application  rate.  All  data  has  been  added  to  the  table  as  site   years.  The  main  effects  are:  

• 6-­‐year  11%  average  increase  in  yield  when  moving  from  fall  to  spring  application  with  1  year  having  

a  71%  increase.  The  average  over  the  other  5  years  is  actually  slightly  negative.  

• 6-­‐year  average  of  8%  increase  in  yield  with  the  addition  of  N-­‐Serve.  One  year  had  a  41%  increase  

with  a  1.6%  increase  excluding  that  year.   Data  was  included  in  the  practice  table.  

(Randall  et  al.,  2003a)  

This  was  a  7-­‐year  study  at  Waseca,  Minn.,  (1987-­‐1993)  with  150  kg  N/ha  application  rate.  This  study  looked   at  timing,  nitrapyrin,  and  sidedress.  Site  years  have  been  added  to  the  table.  Main  effects  are:  

• 7-­‐year  5.4%  average  increase  in  corn  yield  when  moving  from  fall  to  spring.  

• 7-­‐year  10.2%  average  increase  in  corn  yield  when  moving  from  fall  to  pre-­‐plant  +  sidedress  (40-­‐60  

split).  

• 7-­‐year  5.9%  average  increase  in  corn  yield  when  using  nitrapyrin  in  the  fall.  

Data  was  included  in  the  practice  table.    

(Randall  et  al.,  2003b)  

This  was  the  drainage  component  of  the  research  at  Waseca,  Minn.,  from  1987  to  1994.  Nitrogen  

application  rate  was  150  kg  N/ha.  Site  years  have  been  added  to  table  and  include  both  corn  and  soybean.   One  note  is  that  there  was  no  drainage  in  the  soybean  plots  in  1988  or  1989  and  no  drainage  in  the  corn   plots  in  1989.  Main  effects  are:  

• 7-­‐year  6.8%  average  nitrate-­‐N  decrease  when  considering  the  entire  rotation  and  moving  from  fall  

to  spring  nitrogen  application  over  the  study  years.  The  range  was  an  increase  of  80%  in  the   soybean  year  of  1992  and  a  reduction  of  22.9%  in  the  corn  year  of  1990.  

• 7-­‐year  4.8%  average  nitrate-­‐N  decrease  when  considering  the  entire  rotation  and  moving  from  fall  

application  to  a  pre-­‐plant/sidedress  split  (40-­‐60).  The  range  was  an  increase  of  60%  in  the  soybean   year  of  1992  and  a  reduction  of  26.3%  in  the  corn  year  of  1991.  

Data  was  included  in  the  practice  table.    

(Randall  and  Vetsch,  2005a)  

This  research  was  carried  out  at  a  site  in  Waseca,  Minn.,  between  1994  and  2000.  The  study  investigated   nitrogen  loss  from  plots  with  anhydrous  applied  at  135  kg  N/ha  in  the  corn  year  of  a  corn-­‐soybean  rotation.   Information  on  a  full  rotation  was  collected  between  1995  and  1999  with  1994  having  a  corn  crop  only  and   2000  having  a  soybean  crop  only.  Results  show  nitrate-­‐N  concentrations  for  spring-­‐applied  nitrogen  are   lower  than  the  corresponding  fall-­‐applied  treatments  in  the  corn  year.  However,  the  soybean  plots  have   nearly  the  same  nitrate-­‐N  concentrations  for  both  treatments.  All  site  year  data  has  been  added  to  the   practice  table.  This  paper  also  had  information  on  nitrification  inhibitors,  which  was  added  to  the  practice   table.  

(Clover,  2003)  

This  thesis  explored  nitrate-­‐N  concentrations  from  three  years  of  a  corn-­‐soybean  production  in  central   Illinois.  The  treatments  involved  a  fall  and  spring  application  as  well  as  using  a  nitrification  inhibitor.  In   addition  to  the  spring  application  the  study  investigated  a  sidedress  application.  Both  fall  and  spring   treatments  included  a  76  kg  N/ha,  156  kg  N/ha,  and  a  234  kg  N/ha  rate.  The  inhibitor  and  sidedress   treatments  were  applied  at  the  156  kg  N/ha  rate.  Nitrate-­‐N  concentrations  were  lower  coming  out  of  the  

spring-­‐applied  and  fall-­‐application  (depending  on  the  year).  The  timing,  sidedress,  and  inhibitor  numbers   have  all  been  added  to  the  practice  table.