Effects of Short-term Tillage of a Long-term No-Till Land on Quantity and Quality of Organic C and N in Two Contrasting Soil Types

Abstract

Pre-seeding tillage of long-term no-till soil may alter soil quality by changing some properties, but the magnitude of change depends on soil type and climatic conditions. Effects of short-term (2 or 3 years) tillage (hereafter called reverse tillage [RT]) of land previously under long-term no-till (NT, 29 or 30 years), with straw management (straw removed [S Rem ] and straw retained [S Ret ]) and N fertilizer rate (0, 50 and 100 kg N ha -1 in S Ret , and 0 kg N ha -1 in S Rem plots) were determined in autumn 2011 on total organic C (TOC) and N (TON), light fraction organic C (LFOC) and N (LFON), and mineralizable N (N min ) in the 0-7.5, 7.5-15, or 15-20 cm soil layers at Breton (Gray Luvisol [Typic Cryoboralf] loam) and Ellerslie (Black Chernozem [Albic Argicryoll] loam), Alberta, Canada. Short-term RT following long-term NT had no significant negative effect on TOC and TON in soil at both sites, although these parameters tended to be slightly lower in the 0-7.5 cm soil layer with RT compared to NT. For the zero-N treatment, S Ret had greater TOC and TON compared to S Rem in both soil layers at both sites. On average, over both sites, TOC and TON in the 0-15 cm soil increased by 2.08 Mg C ha -1 and 0.216 Mg N ha -1 , respectively. Application of N fertilizer increased TOC and TON in both soil layers, up to the 50 kg N ha -1 rate at Breton (by 7.96 Mg C ha -1 and 0.702 Mg N ha -1 in the 0-15 cm soil) and up to the 100 kg N ha -1 rate at Ellerslie (by 5.11 Mg C ha -1 and 0.439 Mg N ha -1 in the 0-15 cm soil). In both RT and NT treatments, the effects of N rate on TOC and TON were similar for S Ret and S Rem. There was greater LFOC and LFON in the 7.5-15 cm soil layer with RT than NT at both sites. In the 0-15 cm soil layer, averaged over both sites, RT increased LFOC by 66 kg C ha -1 and LFON by 4.0 kg N ha -1 . In both 0-7.5 and 7.5-15 cm soil layers, LFOC and LFON increased with S Ret compared to S Rem. Averaged over both sites, the increase in LFOC and LFON in the 0-15 cm soil was 97 kg C ha -1 and 3.5 kg N ha -1 , respectively. Mass of LFOC and LFON increased dramatically in both soil layers with application of N fertilizer up to the 100 kg N ha -1 rate at both sites, with an average increase of 866 kg C ha -1 and 45.5 kg N ha -1 . In the zero-N treatment, LFOC and LFON increased with S Ret compared to S Rem under RT at Breton and under NT at Ellerslie. On average, tillage had no effect on N min in soil, but S Ret increased N min in soil in both RT and NT, with an average increase of 4.8 kg N ha -1 . Application of N fertilizer increased N min in the 0-20 cm soil up to 50 kg N ha -1 rate at Breton (by 13.7 kg N ha -1) and up to 100 kg N ha -1 rate at Ellerslie (by 18.6 kg N ha -1 ). In conclusion, RT had no effect on TOC, TON and N min in soil, but LFOC and LFON increased with RT compared to NT in the 7.5-15 cm layer at one site. S Ret and N fertilization usually had dramatic positive effects on TOC, TON, LFOC, LFON and N min in soil compared to the corresponding treatments.

Short-term effects of tillage of long-term no-till on nitrous oxide emissions from two contrasting Canadian prairie soils

“…Detailed information on some soil characteristics of both soil types are presented in Table 1. Parallel, long-term experiments with 10 treatments, randomized in four blocks, were established at each site in 1979, and details about the experiments and their management are available in Nyborg et al (1995) and Dyck et al (2016). Barley was grown in 2010 and was most frequently grown crop throughout the experiment ( Table 2).…”

“…The four fertilizer-tillage treatments were maintained for the 2011 growing season, but gas fluxes were not measured. Following the 2011 growing season, soil cores from eight locations in each plot were collected from the 0-7.5, 7.5-15, and 15-20 cm layers using a 2.4-cmdiameter coring tube (Dyck et al 2016). Bulk density of the soil was determined by the core method (Culley 1993).…”

“…The soil samples were air-dried at room temperature after removing any coarse roots and easily detectable crop residues and ground to pass a 2 mm sieve. Subsamples were pulverized in a vibrating-ball mill (Retsch, Type MM2, Brinkman Instruments Co., Toronto, ON, Canada) for determination of total organic C and N, and light fraction organic C and N in various fractions (Dyck et al 2016). Results of these analysis have been reported in detail in Dyck et al (2016), but the results of the light fraction organic N (LFON) as determined with the method of Janzen et al (1992) that was later modified by Izaurralde et al (1997) are included in this work.…”