Changes in carbon and phosphorus storages and humic substances in a Ferralsol, after tillage and animal manures applications

Highlights

• Soil tillage decreased more than 16% of carbon storage at 0.00–0.20 m layer.

• No-till recovered the carbon storage at 0.00–0.10 layer in four years.

• The mainly changes in soil carbon with animal manure applications were qualitative.

• Liquid swine slurry increased humified carbon and P storage regarding poultry manure.

Abstract

The evaluation of the dynamics of storage and loss of soil organic carbon (OC) and available phosphorus, associated with humic substances, in areas under no-tillage (NT) that receive solid or liquid animal manure, has been little reported in the literature. This study aimed to evaluate the effect of different doses of liquid (liquid swine slurry) and solid (poultry manure) animal manures on OC and available phosphorus (P_AV.) storages and humic substances (fulvic and humic acids, and humin) of a Ferralsol recently managed under a no-tillage system (four years). The experiment was carried out in a very clay Ferralsol. Two periods were sampled: in 2011, before tillage for incorporation of chemical fertilizer (CF) and start of the NT system, and in 2015, after four years of NT management and animal manure applications. Poultry manure (PM) and liquid swine slurry (LSS) were applied in three rates as follows: 2.00, 5.00, and 8.00 t ha⁻¹ of PM and 45.00, 90.00, and 135.00 m³ ha⁻¹ of LSS semi-annually applied without CF complementation. The CF was used as a reference. The use of LSS recovered the OC content of the 0.00–0.10 m depth at levels similar to those observed in 2011, indicating the interaction of the liquid form with the soil. The similarity of humic substance between CF and animal manures of the 0.00–0.10 and 0.10–0.20 m depths was mainly due to LSS use, which contents of fulvic and humic acids were significantly higher than those observed in the soil that received PM. Although the use of the LSS increased the SOC content, no difference in storage was observed among the treatments. Soil tillage for NT system start and CF use resulted in a P_AV storage loss of − 2 kg ha⁻¹ yr⁻¹ in 0.10–0.20 m depth from 2011 to 2015. The LSS promoted P_AV. sequestration of up to 33.50 Kg ha⁻¹ yr⁻¹ at 0.00–0.10 m depth and 19.93 Kg ha⁻¹ yr⁻¹ at 0.10–0.20 m depth. The LSS was more effective in increasing P_AV. storage at the two soil depths compared to CF and PM. The fulvic and humic acids were more than two times higher in LSS than in the PM applications at 00.00–0.10 and 0.10–0.20 m depths. Thus, the liquid form has a greater potential to recover OC content and P_AV storage after short-term of NT start (four years), indicating that it is more suitable for the recovery of Ferralsols recently tillage or degraded.

Introduction

The global demand for meat has increased owing to population growth, thus there is an increase in the search for animal species with fast growth rate and high gain/feed ratio. Swine and poultry species show these characteristics; therefore, the intensive production of these species has increased in Europe, North America, Africa, and Brazil (OECD/FAO, 2016). Currently, Brazil is the second largest poultry producer and the fourth swine producer in the world (ABPA, 2020). The manures generated from their productions are commonly used in agriculture as a nutrient source for plants, with great potential to increase soil carbon storage (Benedet et al., 2021, Cavalcante et al., 2019). However, the effects of these manures on soil carbon storage and nutrient dynamics are dependent of their quality and still unclear (Gross and Glaser, 2021, Rodrigues et al., 2021).

Several authors, who have analyzed different climates and soils in Canada, China, Brazil, Africa and several regions of Europe, emphasized that the adoption of no-tillage (NT) does not necessarily increase organic carbon (OC) storage (Blanco-Canqui et al., 2011, Blanco-Canqui and Ruis, 2018, Christopher et al., 2009, Du et al., 2017, Gregorich et al., 2005, Ogle et al., 2019, Palm et al., 2014, Soane et al., 2012); this increase of OC is more unclear when animal manure is applied to soil under NT. Cavalcante et al. (2019) observed an increase in OC and nitrogen storages, mainly up to 0.10 m depth of a Ferralsol that received liquid swine slurry. The use of manure (poultry, swine, or cattle) can be less effective in increasing OC storage in NT soil under tropical or subtropical climate, than in conventional tillage (with disk plow and harrows) soil under non-tropical climate (Gross and Glaser, 2021). Therefore, the use of swine manure may not contribute significantly to the increase in OC storage of a Ferralsol under NT, even after 17 years of application (Oliveira et al., 2017, Tavares et al., 2019). Moreover, the use of animal manure (pig deep-litter, cattle slurry, and swine slurry), can decrease the OC storage in subsurface (0.10–0.20 m) depth, of an Acrisol (Rodrigues et al., 2021).

Low content of available phosphorus (P_AV.) and high sorption capacity of Fe, Al and 2:1 minerals are one of the main limitations to grain productivity in Ferralsols under tropical climate (Bortoluzzi et al., 2015, Oliveira et al., 2020). Moreover, Alewell et al. (2020) observed in literature, that the soils in South America have one of the highest P_AV, depletion rates in the world, especially owing to the low efficiency use of organic phosphorus. From another perspective, the increase of P_AV. can dissolve, thereby destabilizing the OC decreasing its storage in the soil, particularly in Ferralsol (Spohn et al., 2022). Thus, understanding the relationship between the quality and the dynamic of carbon and phosphorus in a Ferralsol, managed under NT that receives solid (poultry manure) or liquid (swine manure) manure, can help to improve the use of the animal manure in agriculture, mainly in tropical climate environment, where there is little information available (Gross and Glaser, 2021, Maillard and Angers, 2014).

One way to assess carbon quality is through humic substances. Humic substances can be changed whit animal manure applications. After four years of applications, Adani et al. (2007) observed that the humic substances present in the soil were more similar to that observed in the manure than that observed as native substances in the soil before application. Thus, humic substances of the organic carbon can be sensitive to chemical changes in the soil caused by poultry and swine manure applications, even after short-term applications.

This study hypothesized that the solid and liquid animal manure may have different effects in the storage recovery and quality of OC and P_AV in soil. Poultry manure may increase the carbon storage, the phosphorus storages and humic fractions of the soil compared to liquid swine slurry, even after short-term applications (four years), especially in the highest doses. Poultry manure is composed of vegetable material with a higher proportion of recalcitrant carbon than swine manure, whereas swine manure is composed of urine, feces, and water with a higher proportion of labile carbon than poultry manure, having an ephemeral effect on soil.

This study aimed to evaluate the effect of different doses of liquid (liquid swine slurry) and solid (poultry manure) manures on the OC storage, P_AV storage and humic substances (fulvic and humic acids, and humin) of a Ferralsol recently managed under a NT system (four years).