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ARS Home » Plains Area » Sidney, Montana » Northern Plains Agricultural Research Laboratory » Agricultural Systems Research » Research » Publications at this Location » Publication #178566
Title: TILLAGE AND CROP ROTATION EFFECTS ON DRYLAND SOIL AND RESIDUE CARBON AND NITROGEN

Author
item Sainju, Upendra
item Lenssen, Andrew
item Caesar, Thecan
item Waddell, Jed

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2005
Publication Date: 2/27/2006
Citation: Sainju, U.M., Lenssen, A.W., Caesar, T., Waddell, J.T. 2006. Tillage and crop rotation effects on dryland soil and residue carbon and nitrogen. Soil Science Society of America Journal. 70(2):668-678.

Interpretive Summary: Conventional tillage and wheat fallow systems in drylands of northern Great Plains have reduced soil organic matter by 30 to 50% of its original level in the last 50 to 100 years. As a result, soil quality and productivity and sustainability of crop production system have been reduced. Improved soil and crop management practices that reduce tillage intensity and fallowing and increase the amount of plant residue returned to the soil are needed to increase soil organic matter and the sustainability of the farming system. We examined the effects of two tillage practices (conventional till and no-till), five crop rotations [continuous spring wheat (CW), spring wheat-fallow (W-F), spring wheat-lentil (W-L), spring wheat-spring wheat-fallow (W-W-F), and spring wheat-pea-fallow (W-P-F)], and a Conservation Reserve Program (CRP) planting on plant biomass (stems + leaves) returned to the soil, residue cover, amount, and C and N contents, and soil organic C, total N, and particulate organic C and N (POC and PON) at 0- to 5- and 5- to 20-cm depths. Each phase of crop rotation (W-F, F-W, W-L, L-W, W-W-F, W-F-W, F-W-W, W-P-F, P-F-W, and F-W-P) (two phases for a two-year rotation and three phases for a three-year rotation) was included in every year. A field experiment was conducted from 1998 to 2003 near Havre, MT. Because of the variations in rainfall, type of crops, and crop rotations, the amount of plant biomass residue returned to the soil varied between crop rotations and years. In general, biomass residue increased with increasing rainfall and cropping intensity. Total biomass residue returned to the soil from 1998 to 2003 was greater in CW than in other crop rotations. Crop residue cover in 2004 was greater in CRP than in other rotations. Residue amount and C and N contents were greater in F-W than in other rotations in conventional till, but was greater in CRP and CW than in other rotations in no-till. Soil organic C and total N at 0- to 5-cm depth were 23 to 31% greater in no-till than in conventional till. The POC was not influenced by tillage and crop rotation, but PON at 0- to 5-cm was greater in NT with CW than in other treatments. From 1998 to 2004, soil organic C and total N at 0- to 20-cm decreased by 3 to 4% in conventional till but increased by 3 to 7% in no-till. The results showed that increasing cropping intensity and reducing fallow periods in crop rotations after six years increased the amount of crop biomass residue returned to the soil. As a result, residue cover was also increased. Reducing tillage increased the amount of residue and C and N contents and soil organic C and total N because of reduced decomposition. Therefore, conservation tillage, such as no-till, and increased cropping intensity can conserve soil C and N in plant residue and soil. This will not only reduce soil erosion but also improve soil quality and productivity and sustain crop yields. The increased levels of soil organic C and total N with these practices can be similar to those with CRP planting.

Technical Abstract: Sustainable management practices are needed to maintain or enhance soil quality and productivity in degraded dryland soils in the northern Great Plains. We examined the effects of two tillage practices [conventional till (CT) and no-till (NT)], five crop rotations [continuous spring wheat (Triticum aestivum L.) (CW), spring wheat-fallow (W-F), spring wheat-lentil (Lens culinaris Medic.) (W-L), spring wheat-spring wheat-fallow (W-W-F), and spring wheat-pea (Pisum sativum L.)-fallow (W-P-F)], and a Conservation Reserve Program (CRP) on plant biomass (stems + leaves) returned to the soil, residue C and N, and soil organic C (SOC), total N (STN), and particulate organic C and N (POC and PON) at 0- to 5- and 5- to 20-cm depths. Each phase of crop rotation (W-F, F-W, W-L, L-W, W-W-F, W-F-W, F-W-W, W-P-F, P-F-W, and F-W-P) was included in every year. A field experiment was conducted in soils mapped as a mixture of Scobey clay loam (fine-loamy, mixed, Aridic Argiborolls) and Kevin clay loam (fine, montmorillonitic, Aridic Argiborolls) from 1998 to 2003 near Havre, MT. Plant biomass yield varied by crop rotation and year and total biomass returned to the soil from 1998 to 2003 was greater in CW and L-W (14.8 to15.3 Mg ha-1) than in other rotations. Residue cover in 2004 was greater in CRP (94%) than in other rotations but residue amount and C and N contents were greater in CT with F-W (3.84 Mg ha-1 and 1594 and 35.7 kg ha-1, respectively) than in other treatments. The SOC and STN contents at 0- to 5-cm in 2004 were 23 to 31% greater in NT (6.4 and 0.81 Mg ha-1, respectively) than in CT. The POC was not influenced by tillage and crop rotation, but PON at 0- to 5-cm was greater in NT with CW (0.42 Mg ha-1) than in other treatments, except in NT with L-W. From 1998 to 2004, SOC and STN at 0- to 20-cm were decreased by 3 to 4% in CT but were increased by 3 to 7% in NT. Carbon and N can be conserved in dryland soils using reduced tillage and increased cropping intensity, such as NT with CW or L-W, compared with traditional practice, such as CT with W-F system, thereby helping to improve soil quality and productivity and reduce erosion. The conserved C and N levels could be similar to those in CRP.