A dataset from a 3-year network of field measurements of soil organic nitrogen mineralization under a mild oceanic temperate climate

Simazine applications of 1.5 p.p.m. to soil in pots in a glasshouse increased dry matter yields and uptake of nitrogen in corn only when additional nitrogen was applied to the soil. The proportions of protein and non-protein nitrogen in the topgrowth were not affected. Application of simazine at this rate without addition of nitrogen resulted in increased leaf area but did not significantly affect yield. Simazine provided a stimulus to the plant early in its life and enabled it to grow faster than the control plant. When the supply of available nitrogen was exhausted the simazine effect decreased. When incubated with soil, simazine did not increase mineralization of soil organic nitrogen, nor did it have any effect on immobilization of mineral nitrogen. Simazine applied at 0.06 p.p.m. in solution culture increased the yield of corn tops by 36%, the uptake of nitrogen by 37%, phosphorus by 25%, magnesium by 24%, and potassium by 41 %. It had no effect on the yields of roots. The results suggest that simazine increased plant growth by a direct effect on plant metabolism and not through any interaction with the soil.

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Do plants use root-derived proteases to promote the uptake of soil organic nitrogen?

Plant and Soil ◽

10.1007/s11104-020-04719-6 ◽

2020 ◽

Vol 456 (1-2) ◽

pp. 355-367

Author(s):

Lucy M. Greenfield ◽

Paul W. Hill ◽

Eric Paterson ◽

Elizabeth M. Baggs ◽

Davey L. Jones

Keyword(s):

Protease Activity ◽

Organic Nitrogen ◽

N Uptake ◽

Root Surface ◽

Organic N ◽

Soil Organic Nitrogen ◽

Poor Access ◽

N Deficiency ◽

Almost All ◽

Soil Protein

Abstract Aims The capacity of plant roots to directly acquire organic nitrogen (N) in the form of oligopeptides and amino acids from soil is well established. However, plants have poor access to protein, the central reservoir of soil organic N. Our question is: do plants actively secrete proteases to enhance the breakdown of soil protein or are they functionally reliant on soil microorganisms to undertake this role? Methods Growing maize and wheat under sterile hydroponic conditions with and without inorganic N, we measured protease activity on the root surface (root-bound proteases) or exogenously in the solution (free proteases). We compared root protease activities to the rhizosphere microbial community to estimate the ecological significance of root-derived proteases. Results We found little evidence for the secretion of free proteases, with almost all protease activity associated with the root surface. Root protease activity was not stimulated under N deficiency. Our findings suggest that cereal roots contribute one-fifth of rhizosphere protease activity. Conclusions Our results indicate that plant N uptake is only functionally significant when soil protein is in direct contact with root surfaces. The lack of protease upregulation under N deficiency suggests that root protease activity is unrelated to enhanced soil N capture.

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Nonhydrolyzable forms of soil organic nitrogen: Extractability and composition

Journal of Plant Nutrition and Soil Science ◽

10.1002/1522-2624(200008)163:4<433::aid-jpln433>3.0.co;2-f ◽

2000 ◽

Vol 163 (4) ◽

pp. 433-439 ◽

Cited By ~ 56

Author(s):

Peter Leinweber ◽

Hans-Rolf Schulten

Keyword(s):

Organic Nitrogen ◽

Soil Organic Nitrogen

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