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 13 2016.

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

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

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

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

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)

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

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

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

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

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

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

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

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