Enhanced nitrogen mineralization in mowed or glyphosate treated cover crops compared to direct incorporation

Abstract

Information on how management by mowing and herbicide alter residue quality and nitrogen (N) inputs would be valuable to improve prediction of N availability. Mowing and glyphosate application are widely used by growers to limit cover crop growth and facilitate incorporation. A mixture of cover crops, hairy vetch (Vicia villosa L.), oriental mustard (Brassica juncea L.) and cereal rye (Secale cereale L.), was investigated as a means to improve soil quality and optimize N availability. There is limited information on how mowing or glyphosate application influence cover crop decomposition and N mineralization from these heterogeneous residues. A rye cover crop was grown in the field over the winter and transferred to containers as an intact soil profile to conduct a greenhouse study. Management treatments (mowing and glyphosate) were imposed eight days before incorporation. Plant and soil N dynamics were monitored. The experiment was repeated with the addition of a tri-mixture cover crop. Inorganic NO − 3 in bare soil ranged from 6 to 10 µg N g soil −1 over 39 days. Similar or lower levels of soil NO − 3 were observed after rye residue incorporation, from 2 to 6 µg N g −1 ; consistent with N-immobilization. Application of untreated, mixed cover crop residues generally was associated with higher levels of soil inorganic NO − 3 , from 3 to 11 µg N g −1 . For both rye and mixed residues, management by mowing or glyphosate enhanced N mineralization by 10 to 100%, compared to untreated residues. At the same time, application of mowing or glyphosate 8 days before cover crop incorporation seemed to reduce the amount of residues by about half compared to untreated controls. Belowground biomass was reduced more than aboveground, although recovery of senescent roots may have been incomplete. Management by glyphosate or mowing enhanced soil inorganic N availability in the short-term while simultaneously reducing carbon and N inputs.

Changing the soil surface management in vineyards: immediate and delayed effects on the growth and yield of grapevine

“…Consequently, as the amount of mineralizable N in the soil was higher, the inorganic N soil content in PIBS was higher than in the other treatments. Snapp and Borden (2005) found the same trend when rye residues were incorporated after mowing: the N mineralization rate was higher than in bare soil 3 weeks after incorporation. Moreover, Corbeels et al (2003) observed that burying crop residues could maintain N fertility in the long term.…”

Root, shoot tissues of Brassica juncea and Cereal secale promote potato health

“…Despite the moderate quantities of mustard residues incorporated, N mineralization potential pool responded; presumably due to the high N content of mustard tissues relative to rye tissues (Table 3). An earlier study of cover crop management supported these findings, as residue quality was the driving factor in N mineralization response of large cores from a related potato systems trial (Snapp and Borden 2005).…”

“…For example, Brassica residues have been shown to alter the soil nematode community structure, which in turn profoundly affects the soil microbial food web, as indicated by studies of biosuppressive effects on plant parasitic nematodes such as Pratylenchus penetrans (Porter et al 1998). Though the level of nitrogen (N) immobilization or release from residues depends on residue quality and other environmental factors, N cycling by Brassicas can influence soil microbial activity and main crop growth (Snapp and Borden 2005). Because of their potential as both a cover and oilseed crop, farmers are particularly interested to know the potential effects of incorporating different rates and types (roots versus shoots) of Brassica tissues on disease suppression and root health within typical field conditions.…”

Effect of pendimethalin and quizalofop on N2-fixing bacteria in relation to availability of nitrogen in a Typic Haplustept soil of West Bengal, India

“…The stimulation of microorganisms and their activities due to the application of herbicides brought about greater mineralization of organic nitrogen resulting in greater amount of available nitrogen (Snapp and Borden 2005) and subsequent loss of nitrogen from soil due to volatilization by the microorganisms (Smith and Weeraratna 1974; Tables 3 and 4). In general, application of pendimethalin and quizalofop either alone or in combination retained higher amount of total nitrogen as compared to untreated control (Table 3).…”