Organic carbon and nitrogen contents and their fractions in soils with onion crops in different management systems

Abstract

The use of plant species in rotation or succession of crops can increase C and N contents and their fractions in the soil. The objective of this study was to evaluate the effect of using soil cover crops in succession and rotation with onion crops in different soil management systems on the total organic carbon (TOC), total nitrogen (TN), and C and N fractions in soil aggregates, and bulk soil. The experiment was implemented in April 2007 with eight treatments: succession of onion and maize in a no-tillage system (NTS) (T1); rotation of soil cover crops (winter) and biennial onion in a NTS (T2); rotation of maize, winter grasses, and onion in a NTS (T3); succession of summer legume and annual onion in a NTS (T4); rotation of summer grass, winter grasses, and annual onion in a NTS (T5); succession of summer legume, winter grass, and annual onion in a NTS (T6); succession of maize and onion in a conventional tillage system (CTS) (T7); and succession of intercrops of soil cover crops (summer), and annual onion in a NTS (T8). Undisturbed soil samples were collected in the 0.0–5.0, 5.0–10.0, and 10.0–20.0cm soil layers in July 2014, and their aggregate (8.0 to 2.0mm) and bulk soil (<2mm) fractions were separated to evaluate their TOC, TN, particulate organic carbon and particulate organic nitrogen (OCP and ONP respectively), and mineral-associated organic carbon and mineral-associated organic nitrogen (OCM and ONM respectively). Soil turning due to the CTS in T7 (0.0–5.0cm) reduced TOC, OCP, OCM, TN, ONP, and ONM, in the soil aggregates and in the bulk soil, when compared with the NTS with the use of soil cover crops in succession or rotation with onion crops (T1–T6 and T8). T6 increased the TOC, TN, OCP, OCM, ONP, and ONM contents in the soil aggregates and bulk soil when compared with the successions with only grasses or only legumes. T1 increased the soil TOC and TN contents in aggregates compared with the same succession in CTS. T8 had higher OCP (0.0–20.0cm) and ONP (5.0–10.0cm) contents in aggregates than in the bulk soil. In general, aggregates had higher TOC and OCM contents, and bulk soil had higher TN, OCP, ONP and ONM contents. The main changes resulting from the management systems and soil cover crop combinations used were observed in the particulate fraction, especially in the soil aggregates.

Soil Carbon, Glomalin, And Aggregation in Onion Crop Under No-Tillage with Cover Crops or Conventional Tillage Systems for Eight Years

“…The lowest TOC contents in CTS always occurred in the bulk soil compared with TOC in aggregates. Ferreira et al (2018) found higher TOC contents in the bulk soil in CTS. That probably was due to the rupture of soil aggregates, which accelerated the decomposition of SOM protected inside aggregates, leading to increases in the SOM decomposition rate and lower TOC contents in the bulk soil.…”

“…Cover crop species improve soil physical and chemical attributes in onion fields (Loss et al, 2017;Comin et al, 2018a;Santos et al, 2018;Ferreira et al, 2018) as well as soil biological properties (Silva et al, 2014). They also lead to lower weed emergence, affecting onion yield and quality (Vilanova et al, 2014;Oliveira et al, 2016;Comin et al, 2018b;Souza et al, 2018).…”

“…Cover crops affect both SOM accumulation and soil aggregation, responsible for soil structure and SOM protection. Some studies relate those gains with cover crops' ability to form a dense, fasciculate root system, with rapid establishment and exploration of the soil profile at greater depths (Loss et al, 2017;Ferreira et al, 2018).…”

Subsoiling during summer fallow in rainfed winter-wheat fields enhances soil organic carbon sequestration on the Loess Plateau in China

“…In comparison with plow tillage, no tillage for six years resulted in a 5.3 Mg ha -1 increase in the SOC stock at the 0–10 cm soil depth, and 38% of the SOC accumulation occurred in the MOC fraction [ 23 ]. Ferreira et al [ 24 ] shows that the MOC concentration under no tillage in the 0–5 cm soil layer was lower than that under plow tillage, whereas Plaza et al [ 25 ] reports that the MOC concentration was16% higher in no tillage plots than in plow tillage plots. However, Blanco Moure et al [ 26 ] showed that no change in MOC concentrations under tillage practices occurred under rainfed Mediterranean conditions.…”

Efeito da sucessão ou rotação de culturas sobre a fertilidade do solo após sete anos de cultivo com cebola

“…A literatura reporta que o cultivo de cebola em SPC provoca profundas alterações em atributos edáficos do solo, além de reduzir a disponibilidade de nutrientes às plantas e o seu conteúdo de matéria orgânica (Loss et al, 2015, Santos et al, 2017Comin et al, 2018;Ferreira et al, 2018).…”