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ARS Home » Plains Area » Sidney, Montana » Northern Plains Agricultural Research Laboratory » Agricultural Systems Research » Research » Publications at this Location » Publication #337599
Title: Soil nitrogen fractions under long-term crop rotations in the Loess Plateau of China

Author
item FU, XIN - Northwest University
item WANG, JUN - Northwest University
item Sainju, Upendra
item LIU, WENZHAO - Northwest University

Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2018
Publication Date: 10/12/2018
Publication URL: https://handle.nal.usda.gov/10113/6178917
Citation: Fu, X., Wang, J., Sainju, U.M., Liu, W. 2018. Soil nitrogen fractions under long-term crop rotations in the Loess Plateau of China. Soil and Tillage Research. 186:42-51. https://doi.org/10.1016/j.still.2018.10.004.
DOI: https://doi.org/10.1016/j.still.2018.10.004

Interpretive Summary: Nitrogen is a major limiting nutrient for achieving sustainable crop yields in dryland cropping systems. Nitrogen fertilization can enhance crop yields and quality, but excessive fertilization can reduce soil and environmental quality by increasing soil acidification, nitrogen leaching, and greenhouse gas (nitrous oxide) emissions. By increasing nitrogen-use efficiency, enhancing nitrogen storage, and reducing nitrogen fertilization rate through improved management practices, nitrogen losses to the environment can be minimized compared with traditional practices. Little is known about the effect of long-term management on nitrogen dynamics in the Loess Plateau of China. We studied the long-term (30 yr) effect of crop rotations on soil nitrogen fractions at 0-15 and 15-30 cm depths in the Loess Plateau of China. Crop rotations were continuous winter wheat (W), 3-yr rotations of corn-winter wheat-winter wheat-millet (CWWM), pea-winter wheat-winter wheat-millet (PWWM), and sainfoin-winter wheat-winter wheat-sainfoin (SWWS); 4-yr rotation of pea-winter wheat-winter wheat-corn (PWWC); and 8-yr rotation of alfalfa (4 yr)-potato (1 yr)-winter wheat (3 yr) (A4PoW3). A fallow (F) treatment was also included for comparison. Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), ammonium-nitrogen (NH4–N), and nitrate-nitrogen (NO3–N). The STN and PON at 0-15 cm were greater with CWWM and at 15-30 cm greater with A4PoW3 than F and W. The PNM at both depths was greater with A4PoW3 than other crop rotations, except SWWS and CWWM. The MBN was greater with CWWM, PWWM, SWWS and A4PoW3 than other crop rotations. The NH4-N content was greater with F than other crop rotations, except PWWC. The NO3-N content at 0-15 cm was greater with CWWM and at 15-30 cm greater with PWWM than F. Soil nitrogen fractions were linearly related with the estimated mean annualized root biomass nitrogen, except for PON and PNM at 15-30 cm. Most soil nitrogen fractions were correlated with each other and also with the length of the crop rotation. Diversified crop rotations with increased root biomass N returned to the soil and longer year rotations enhanced soil N storage, mineralization, and availability compared with monocropping and fallow. As a result, diversified crop rotation can reduce N fertilization rate reduce N loss to the environment, and sustain crop yields and quality.

Technical Abstract: Long-term crop rotation may influence soil N storage, mineralization, and availability and therefore the sustainability of the crop production system. We studied the long-term (30 yr) effect of crop rotations on soil N fractions at 0-15 and 15-30 cm depths in the Loess Plateau of China. Crop rotations were continuous winter wheat (Triticum aestivum L.) (W), 3-yr rotations of corn (Zea mays L.)-winter wheat-winter wheat-millet (Eleusine coracana L.) (CWWM), pea (Pisum sativum L.)-winter wheat-winter wheat-millet (PWWM), and sainfoin (Onobrychis viciifolia Scop.)-winter wheat-winter wheat-sainfoin (SWWS); 4-yr rotation of pea-winter wheat-winter wheat-corn (PWWC); and 8-yr rotation of alfalfa (Medicago sativa L.) (4 yr)-potato (solanum tuberosum L.) (1 yr)-winter wheat (3 yr) (A4PoW3). A fallow (F) treatment was also included for comparison. Nitrogen fractions were soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), potential N mineralization (PNM), NH4–N, and NO3–N. The STN and PON at 0-15 cm were greater with CWWM and at 15-30 cm greater with A4PoW3 than F and W. The PNM at both depths was greater with A4PoW3 than other crop rotations, except SWWS and CWWM. The MBN was greater with CWWM, PWWM, SWWS and A4PoW3 than other crop rotations. The NH4-N content was greater with F than other crop rotations, except PWWC. The NO3-N content at 0-15 cm was greater with CWWM and at 15-30 cm greater with PWWM than F. Soil N fractions were linearly related with the estimated mean annualized root biomass N, except for PON and PNM at 15-30 cm. Most soil N fractions were correlated with each other and also with the length of the crop rotation. Diversified crop rotations with increased root biomass N returned to the soil and longer year rotations enhanced soil N storage, mineralization, and availability compared with monocropping and fallow.