For estimating plant- available N in soil testing laboratories there is no universally accepted method (like Olsen and Brays methods for P).Both biological and chemical methods used for estimating mineralizable N have limitations.As I understand some private laboratories in USA are using anaerobic incubation method of short duration(7days) as soil N test.Can that be adopted for routine N soil testing in soil testing laboratories?Any other countries have experience in this line?Also, what is the experience of soil scientists in use of profile nitrate test for routine soil testing for N?
all tests for available N in soils as a means for fertilizer recommendation have never worked out properly, which is due to the high variability of N and its mobilization, transformation and transport features in time and space: the best way to deal with N is accurate balancing!
Ewald is spot on. In environments with limited leaching, nitrate measurements before sowing are a useful guide
I attached these works made in Argentina that may be of your interest.
Regards,
Walter
Dr.Schnug,I appreciate your answer but how the soil testing laboratories implement it in advising famers in efficient use of fertilizer N to different crops or cropping systems?
Dr.Milham,I understand that profile nitrate-N test can give an estimate of readily available soil N for crops and is also being used in some states in USA and Canada.But sampling depth- wise soil samples upto 60cm may be difficult.Also in developing countries estimaing nitrate N in soil testing labs(with reliable and convenient method) may also be difficult as the amount of nitrate present in soil after the harvest of the previous crop may small.
Dr.Carciochi,Thank you for attaching relavent and good literature.I am looking for such work.But my main concern is how to translate/transfer the research information to soil testing laboratoies for recommending N fertilizers to farmers under field conditions.
My colleagues have looked into different N test used to make fertilizer recommendations for sugarcane. They then related responsiveness of sucrose yield to N applications with these test. An r2 of 0.71 was found when anaerobic N was used.
PS: Their work will appear in the 2017 Proceedings of the South African Sugar Technologists Association
Dr.Elephant, good information.There have been good number of papers/reports in support of anaerobic incubation method from different countries but the government laboratories haven't taken a decision on merit of this method to include it in regular soil testing program for assessing N availability.
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