Soils organic residue

Preferential flow through root-mediated soil pores has been demonstrated for chloride, nitrate, and other ions that are not sorbed onto soil organic matter and clays. However, pesticide sorption onto soil affects both mobiUty of the pesticide as well as its residual life in the soil. Pesticide sorption onto root organic matter or organic linings of worm burrows may also slow transport of pesticides relative to water (72), thus countering the effects of increased permeabihty caused by roots. 

Verstraete W, W Devlieger (1996) Formation of non-bioavailable organic residues in soil perspectives for site remediation. Biodegradation 7 471-485. 

Neutral interactions are found extensively in the rhizosphere of all crop plants. Saprophytic microorganisms are responsible for many vital soil processes, such as decomposition of organic residues in soil and associated soil nutrient mineralization/turnover processes. While these organisms do not appear to benefit or harm the plant directly (hence the tenn neutral), their presence is obviously vital for soil nutrient dynamics and their ab.sence would clearly influence plant health and productivity. 

Table 2 Cumulative CO, Evolution from Root Residues (RM), Soil Organic Matter (SOM), and Glucose During 24 Days of Incubation...

By sharply decreasing biodiversity in the soil ecosystem, pesticides negatively affect all soil organisms on which soil productivity depends. Pesticides affect the biological activity in soil, especially through long-term use and accumulation (or accumulation of their residues). 

Kogel-Knabner, I. (2002). The macromolecular organic composition of plant and microbial residues as inputs to soil organic matter. Soil Biology and Biochemistry 34 139-162. 

Calculation of the microbial quotient can make treatment effects much more obvious. For example, in Fig. 2 the microbial quotient was greater in the row than inter-row and greater under residue return than burning, both to a depth of 30 cm. In addition, values declined with depth as soil organic matter content declined and the proportion of organic C present in labile form declined. 

Grayston SJ, Vaughan D, Jones D (1996) Rhizosphere carbon flow in trees, in comparison with annual plants the importance of root exudation and its impact on microbial activity and nutrient availability. Appl Soil Ecol 5 29-56 Gregorich EG, Ellert BH, Monreal CM (1995) Turnover of soil organic matter and storage of com residue carbon estimated from natural 13C abundance. Can J Soil Sci 75 161-167... 

Schweizer M, Fear J, Cadish G (1999) Isotopic (13C) fractionation during plant residue decomposition and its implications for soil organic matter studies. Rapid Commun Mass Sp 13 1284-1290... 

SOC NHC NHCa NHC m "initial socM Soil organic carbon Non-harvested crop residues Amount of non-harvested carbon applied Non-harvested carbon maintenance requirement Soil organic carbon at the beginning of the experiment Soil organic carbon contained in soil at the end of the Experiment... 

C SOC retained SOClost SOC sSOC SOC SOC n Associated 813C value Amount of organic carbon lost Rayleigh fractionation constant of the SOC Soil organic carbon derived from com stover Total corn-derived carbon in the residue returned treatment Com derived from unharvested material in the stover harvested treatment... 

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