Total aboveground biomass usually increases in the presence of legumes Tilman et al. Eisenhauer et al. Strecker et al. Our finding of negative effects of functional group richness and presence of legumes on net ammonification Table S6 contrasts the literature, which has up to now mainly reported positive plant diversity effects on net turnover rates Rosenkranz et al.
The literature also suggested that the presence of legumes increased the net N release Scherer-Lorenzen et al.
However, Fischer et al. Thus, the decreasing soil water contents with increasing species richness in the year might explain the negative effect of functional group richness on net ammonification. Our finding that the presence of legumes decreased net ammonification after the effects of block and species richness had been considered is unexpected Table S6.
Again unexpectedly, functional group richness had negative effects on net ammonification rates, which we attribute to the decreasing soil moisture in topsoil with increasing plant diversity in the year of our study This positive effect likely explained the negative effect of the presence of legumes on net ammonification. Among the wealth of data from the Jena Experiment, only the root C:N ratio was identified to significantly reduce two of the three studied gross N turnover rates, but explained a small portion of the total variance in our structural equation model.
The root C:N ratio likely increased with increasing species richness because of a species replacement effect from legumes to forbs and because of increasing competition for light which resulted in a higher mean shoot height associated with a lower C:N ratio of the above- and belowground biomass. The negative root C:N ratio effect overwhelmed a positive effect of microbial biomass on gross N mineralization and microbial N consumption.
Our results illustrate that the nutrient composition of biomass mediates N turnover processes in the studied grassland ecosystem suggesting that connecting ecological stoichiometry with nutrient fluxes could be a promising avenue to better understanding the biodiversity—nutrient cycling relationship. We hypothesize that the latter is related with a changing microbial composition with increasing species richness, for which we lack data.
Therefore, future experiments should be designed to elucidate the relationships between species richness, microbial community composition and N turnover rates. Generally, relating soil nutrient fluxes with microbial community composition could additionally improve our understanding of the controls of nutrient turnover in soil.
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You can also search for this author in PubMed Google Scholar. Correspondence to Sophia Leimer. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material.
If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. Reprints and Permissions. There are many management techniques we can use in our soils that can promote the mineralization of nitrogen throughout the growing season of corn and other commodities.
First, it's important to consider the carbon to nitrogen ratio of cover crops when they're terminated. Certain cover crops like cereal rye have the potential to immobilize nitrogen if they're terminated at a late and highly mature stage. The residual organic nitrogen content of manure from previous years of applications can be a significant source of additional mineralized nitrogen and should be accounted for in cropping plants. Additionally, improving the drainage of agricultural fields can help to increase the amount of nitrogen that is made available to growing plants by helping the soil to remain at the optimal moisture level for microbial activity.
It also reduces the risk of nitrogen loss to denitrification, a microbial process that occurs in oxygen-depleted soils. By being aware of the cycle that nitrogen must go through to become available to crops, we can be better stewards of those nutrients and get the most out of our fertilizer dollar. Only registered users can write reviews.
Please, log in or register. All answers will be displayed after moderation. Next Questions. By Charles White. By Sjoerd Willem Duiker, Ph. Immobilization and Mineralization of Nitrogen in Agricultural Soils. Nitrogen availability in soils is controlled by a process called the nitrogen cycle. This video explores two pieces of the cycle - immobilization and mineralization. Videos Length: Description Nitrogen is a key nutrient necessary for plant growth and development.
Instructors Casey Guindon. View Transcript arrow thudding arrow clicking - Let's talk about nitrogen. Plants can only absorb nitrogen from the soil in the form of nitrate or ammonium.
Soil microbes play a vital role in the amount of nitrogen that becomes available to plants. This process is called the immobilization of nitrogen. Additionally, an ideal soil moisture for plant growth also optimizes microbial activity.
Let's see the process of mineralization and immobilization in action. These three pots represent soils with different additives. The pot on the right without a label contains only soil. No nitrogen containing amendments were added. The middle, labeled S, contains soil with ground wheat straw added. National Agricultural Library. Active Data provider submitted metadata in the last calendar year. Journal Article. Access the full text Link Link.
Lookup at Google Scholar. Prediction of net N mineralization is required for optimization of the synchronization of N supply with plant N demand. Net N mineralization is the outcome of two concurrent and oppositely directed processes: gross N mineralization and gross N immobilization turnover MIT.
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