The effect of integrated management practices on crop and soil nutrient dynamics
Slawinski, K.R. 2010. University of Manitoba
Abstract
This study was undertaken to evaluate the pattern of release and uptake of N for durum
wheat (Triticum durunt Desf. cv. AC Avonlea) grown on field pea(Pisum sativaL.)
stubble in 2002 and 2003 under a range of management systems including (i) organic (no
inputs), (ii) organic with composted beef cattle (Bos taurus) manure, (iii) synthetic
fertllizer, no pesticides, (iv) Pesticide Free Production (PFPTM) (synthetic fertilizer,
pesticides used before crop growth and in other crops in the rotation, no pesticides
applied to the growing target crop and no residual pesticides) and (v) integrated
management (synthetic fertilizer, pesticides applied as required). Regardless of
management system, the greatest soil NO3- contents were generally observed between the
time of seeding and the first crop stage sampled with maximum crop N accumulation
occurring by anthesis. Measured soil and crop N variables tended to be greatest in
systems receiving synthetic fertilizer. The strictly legume and legume and composted
manure based fertility systems were not able to supply sufficient N for optimum crop
production based on a sufficiency N concentration of 2 to 3%o in the whole plant prior to
filling. Systems receiving synthetic urea fertilizer without pesticides also experienced N limitations in response to competition from significantly higher weed biomass. The
PFP™ system was able to produce dry matter and final grain yields comparable to the
integrated management system suggesting effective crop production may be possible in a
reduced pesticide system as long as adequate nutrients are available to meet crop demand.
The effectiveness of Plant Root SimulatorrM (PRS) probes and the Illinois soil N test (ISNT) for predicting soil N release through the growing season were also evaluated.
Good relationships were found between mid season PRS-NO3- and crop N uptake (r:
0.5 1 * and 0.64* *) in 2002 and 2003 respectively. Although a greater correlation was
observed between mid season soil NO3- content and crop N uptake compared to mid
season PRS-NO3- and crop uptake, no significant correlation was observed between early
season NO3- concentrations and crop N uptake. There was no correlation between ISNT-
N and crop N uptake in either year of study. The ISNT was not a reliable indicator of
potential N release under Manitoba conditions, based on the critical value of 300 mg kg-l
suggested for soil samples collected from a 0-15 cm depth from corn sites in lllinois. The
lack of strong, consistent relationships between early season assessment of N release potential and crop N uptake make it difficult to use these indices for adjusting
recommended fertilizer rates.
