Response of Soil Organic Carbon, pH, Electrical Conductivity, and Water Stable Aggregates to Long‐Term Annual Manure and Inorganic Fertilizer

Abstract

Core Ideas Long‐term annual application of manure maintained the soil pH but inorganic fertilizer decreased it. Manure application increased soil organic carbon (SOC) and total nitrogen (TN). Higher manure rate helps in improving the water stable aggregates compared to inorganic fertilizer at 0‐ to 10‐cm depth. Manure enhances soil fertility and crop yield; however, an optimum rate of manure application is important to avoid any negative impacts to soils and the environment. This study was conducted to assess the long‐term impacts of manure and inorganic fertilizer rates on soil organic carbon (SOC), total nitrogen (TN), water stable aggregate (WSA), pH, and electrical conductivity (EC) under corn (Zea mays L.)‐soybean (Glycine max L.) rotation at Beresford (established in 2003) and Brookings (established in 2008), South Dakota (SD). Study treatments included low (LM), medium (MM) and high (HM) manure, medium (MF) and high (HF) inorganic fertilizer, and control (CK). Soil samples were extracted from four replicates at 0‐ to 10‐cm, 10‐ to 20‐cm, 20‐ to 30‐cm and 30‐ to 40‐cm depths from either site in 2015. Results showed that manure application maintained the soil pH at 0 to 10 cm depth; whereas, inorganic fertilizer decreased it compared to the control treatment at either site. The highest SOC concentrations at 0‐ to 10‐cm depth were observed under HM (38.3 g kg–1) as compared to that under MM (30.9 g kg–1), LM (27.6 g kg–1), MF application (24.0 g kg–1), HF (25.8 g kg–1) and CK (23.3 g kg–1). Furthermore, HM treatment significantly increased SOC for each depth increment from 0‐ to 40‐cm compared to the inorganic fertilizer at either site. A similar trend was observed for the TN but differences were not always significant. On an average, manure increased the EC (1.56 dS m–1) by 2.2 times compared to that of fertilizer (0.71 dS m–1) for 0‐ to 10‐cm depth. Similarly, manure significantly increased WSA by 7.2 and 5.6% compared to that of fertilizer at 0‐ to 10‐cm depth for Brookings and Beresford, respectively. Data from this study concluded that the long‐term annual application of manure improved selected soil properties compared to that of inorganic fertilizer.

Depth Distribution of Bulk and Aggregate-Associated Manganese Oxides Mediated by Soil Chemical Properties in a Long-Term Fertilized Paddy Soil

“…It is noticed from this current study that fertilizer treatment 30F recorded the highest pH values whereas NPK recorded the lowest at both depths compared to other treatments. This finding agrees with that of Ozlu and Kumar (2018) who observed that higher manurecontaining fertilizers increased pH values compared to higher doses of chemical fertilizer sources. The decline in pH values noticed in the NPK treatment in our current study could be connected with nitrification and acidification activities (Liang et al 2012).…”

“…It is clearly observed from this study that the long-term fertilizer treatments markedly impacted on pH values in the surface layer only. Ozlu and Kumar (2018) and Liang et al (2012) also noticed similar trends, where fertilizer treatments considerably influenced the pH values in the 0-10 and 10-20 cm compared to the 20-30 and 30-40 cm layers. It is noticed from this current study that fertilizer treatment 30F recorded the highest pH values whereas NPK recorded the lowest at both depths compared to other treatments.…”

“…The decline in pH values noticed in the NPK treatment in our current study could be connected with nitrification and acidification activities (Liang et al 2012). However, a holistic observation of the general superior pH values in the other treatments compared to NPK suggests that the inclusion of organic fertilizer sources could have raised the pH values mainly through proton depletion by functional groups linked to organic materials, carboxylation of organic acid anions during decomposition, and specific adsorption of organic molecules which liberate OH − ions (Ozlu and Kumar, 2018). In general, soil pH values in all treatments were observed to be significantly (P ≤ 0.05) lower in the surface compared to the subsurface layer (Table 1).…”

“…In general, soil pH values in all treatments were observed to be significantly (P ≤ 0.05) lower in the surface compared to the subsurface layer (Table 1). This could be attributed to organic acids liberated via manure input as well as protons liberated by roots promoted through the long-term fertilization (Ozlu and Kumar, 2018;Liang et al 2012) in the study area. Fertilizer treatment 30F profoundly influenced the distributions of both TOC and TN, where it recorded significantly (P ≤ 0.05) higher concentrations of these parameters in bulk soil and aggregate sizes at both depths.…”

The Problem of Comprehensive Analysis of Organic Agriculture as a Factor of Environmental Safety

“…Organic fertilizers (manure, humus, etc.) are known to contain nutrients [35] in a safe form for plants and the environment. Accordingly, that is why they are recommended for use by Council Regulation (EC) No.…”