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United States Department of Agriculture

Agricultural Research Service

Title: Soil Carbon and Nitrogen Pools under Long-Term Productivity of Rhizoma Peanut and Perennial Weeds Management Systems

Authors
item Sainju, Upendra
item Terrill, Thomas - FORT VALLEY STATE UNIV
item Gelaye, Seyoum - FORT VALLEY STATE UNIV
item Singh, Bharat - FORT VALLEY STATE UNIV

Submitted to: Archives of Agronomy and Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 22, 2005
Publication Date: February 1, 2006
Citation: Sainju, U.M., Terrill, T.H., Gelaye, S., Singh, B.P. 2006. Soil carbon and nitrogen pools under long-term productivity of rhizoma peanut and perennial weeds management systems. Archives of Agronomy and Soil Science. 52:45-59.

Interpretive Summary: Rhizoma peanut is a warm-season perennial legume forage that survives well in the Coastal Plain of southeast USA. As the above- and belowground biomass grow in the summer, they start to fix both carbon (C) and nitrogen (N) from the atmosphere. Although the aboveground biomass is harvested for animal forage every year, belowground biomass is left in the soil, part of which decays and forms an important source of C and N inputs for soil organic matter. As new growth of roots appears and aboveground biomass grows every year, C and N inputs from the leftover aboveground biomass after harvest and belowground biomass are continuously added to the soil. As a result, long-term productivity of rhizoma peanut may enrich both C and N, thereby increasing soil microbial activities, nitrogen mineralization, and organic matter compared with perennial weeds. Little is known about the seasonal and long-term effects of above- and belowground biomass of rhizoma peanut and perennial weeds on soil C and N pools. As temperature increases from spring to summer, soil microbial activity increases. As a result, mineralization of organic C and N increase, thereby increasing the levels of labile and available pools of soil C and N. Because of the increased growth of biomass and N accumulation in peanut compared with weeds, the amount of C and N inputs supplied by peanut also increase. As a result, seasonal and long-term levels of soil C and N pools may be greater under peanut than under weeds. We examined seasonal and long-term effects of biomass yield, N accumulation, and root length density from 0 to 70 cm depth of 10-yr-old rhizoma peanut and perennial weeds [dominated by henbit and cut-leaf evening primrose] on soil organic C, total N, ammonium-nitrogen (NH4-N), nitrate-nitrogen (NO3-N), potential C and N mineralization (PCM and PNM), microbial biomass C and N (MBC and MBN), and particulate organic C and N (POC and PON) from June to October, 2000 and 2001. In order to measure the effect of rhizoma peanut on soil organic matter level, C and N pools under peanut and nonlegumes or some native species, such as naturally occurring weeds within the region, were measured for comparison. Biomass yield and N accumulation in peanut and weeds increased from June to October, 2000 and 2001, and were greater in peanut than in weeds from July to October. Root length density increased from June to September and was greater in peanut than in weeds in September. Soil C and N pools varied at certain times of the year during crop growing season and were greater under peanut than under weeds. Like plant biomass, C and N pools did not vary linearly with sampling date, except NH4- and NO3-N. Regardless of dates, organic C, total N, POC, PON, MBC, MBN, PCM, PNM, and NO3-N were greater under peanut than under weeds. Short-term productivity of rhizoma peanut may enrich soil N availability while long-term productivity may improve soil quality and productivity by increasing microbial activities, N mineralization, and C and N sequestration compared with perennial weeds. Nonlegume forage may be grown together with rhizoma peanut to use the available pool of N supplied by peanut without the need for the application of N fertilizer if there is no competition in growth between the species. The increase in soil organic C and N resulted from long-term productivity of rhizoma peanut may also help to alleviate some problems of global warming.

Technical Abstract: Short- and long-term productivity of rhizoma peanut [(Arachis glabrata Benth.), a warm-season perennial legume forage] may improve soil quality and fertility by increasing organic matter and N mineralization compared with perennial weeds. We examined seasonal and long-term effects of biomass yield, N accumulation, and root length density from 0 to 70 cm depth of 10-yr-old rhizoma peanut and perennial weeds [dominated by henbit (Lamium amplexicaule L.) and cut-leaf evening primrose (Oenothera laciniata L.)] on soil organic C, total N, NH4-N, NO3-N, potential C and N mineralization (PCM and PNM), microbial biomass C and N (MBC and MBN), and particulate organic C and N (POC and PON) from June to October, 2000 and 2001. Field plots were established on a Norfolk loamy fine sand (fine-loamy, siliceous, thermic Typic Kandiudults) in April 1991 in central Georgia. Biomass yield and N accumulation in peanut and weeds increased from June to October, 2000 and 2001, and were greater in peanut than in weeds from July to October. Root length density increased from June to September and was greater in peanut than in weeds in September. Soil total N in June, July, and October 2000 and July 2001, POC in June, July, and October 2000 and from July to September 2001, PON in June and October 2000 and July 2001, MBC in July and September 2001, MBN in August to October 2000 and August to September 2001, PCM in July 2001, PNM in September 2001, NH4-N in June and October 2000, and NO3-N in August 2000 and September 2001 were greater under peanut than under weeds. Like plant biomass, C and N pools did not vary linearly with sampling date, except NH4- and NO3-N. Regardless of dates, organic C, total N, POC, PON, MBC, MBN, PCM, PNM, and NO3-N were greater under peanut than under weeds. Short-term productivity of rhizoma peanut may enrich soil N availability while long-term productivity may improve soil quality and productivity by increasing microbial activities, N mineralization, and C and N sequestration compared with perennial weeds.

Last Modified: 12/19/2014
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