1. Bioscience conference, Berlin, Germany
Nitrogen mineralization dynamics of different valuable organic amendments commonly used in agriculture
Uzokwe, V.N., Masunga, R.H., Mlay, P.D., Odeh, I., Singh, A., Buchan, D., De Neve, S.
Bioscience conference, Berlin, Germany
Septmber, 12 to

2. Summary
We examined how four common organic amendments affected soil properties-contributing to soil fertility and micro-biota changes over time
We show how these organic amendments can be used to restore and reclaim degraded soils-better mineral N over time than manures compost
Using clover as an organic amendment gives better nitrogen mineralization and stimulates microbial activity more effectively than the composts and manures

3. Why is this research important?
Organic soil amendments are an important part of sustainable agricultural strategies, but require careful management to improve soil fertility
Timing and amount of nitrogen mineralization are important for maintaining soil quality
However, the differences between various types of organic amendments have not yet been studied

4. Background Organic soil amendments
Recycle nutrients and organic matter
Support crop productivity
Maintain soil quality
Soil nutrient pool
Plant nutrient pool

5. Factors affecting N mineralization
Climate
Temperature, moisture
Chemical composition of organic material
C:N ratio, N content,
Bio-chemical properties of the materials
Lignin, celulose, hemicelulose content and polyphenols

6. Methods
Surface soil samples taken from a research farm in Merelbeke, Belgium (Institute for Agriculture
and Fisheries Research)
Control
(soil only)
Soil + clover
200g of soil (depth 0 – 20cm) was placed in plastic tubes and mixed with OA at different rates; soil had low N content of 0.09 % with pH (KCl) of 5.5
Soil + veg, fruit, yard waste compost
Soil + poplar tree compost
Soil + cattle manure
Amended soil incubated for 97 days and analyzed at 7, 21, 40, 68 and 97 days intervals for N and microbial biomass carbon (MBC)

7. Application rates of organic amendments
Application rates of the OA used for incubation Exp.
Organic amendment
Soil
Water
Application rates of organic amendments
moist
dry basis
(g tube-1)
(ml)
(kg N ha-1)
(t ha-1)
COI
200
2.2
4.28
2.09
126.5
5.8
COV
1.0
2.57
1.59
127.6
4.4
CLO
3.9
5.59
0.73
126.0
2.0
MAN
4.3
4.82
1.39
125.4
3.8

8. Results The soils amended with Clover had the highest N mineralization
Composts and cattle manures were moderate, however, above the control treatment
The maximum mineralized N was at 40 days for the COI and manures and at 68 days for Clover and COV

9. Results Control Poplar tree Vegetable, fruit and yard waste Clover
Cattle manure

10. Results…
The soils amended with Clover had the highest N mineralization
Control (soil alone) released the lowest mineral N
Composts (COI & COV) and manures were moderate

11. Results.. MBC peaked at ~21 days of incubation in all OA
Clover had the highest MBC by the end of experiment compared to the rest

12. Results…….. MBC peaked at ~21 days of incubation in all OA
Clover had the highest MBC by the end of experiment
Control
Poplar tree
Vegetable, fruit and yard waste
Clover
Cattle manure

13. Conclusion
Clover produced the highest mineral N of the organic amendments studied (due to high N content of the material and low C:N ratio)
Clover may be the best organic source of N for crops production
However, nitrogen dynamics are complex and also depend on many other factors
These findings will help guide policy on choice and timing of organic amendments

14. Next steps/future work
Test our laboratory incubation results in field experiments
Nutrient mineralization from organic amendments should be studied alongside crop uptake