The interaction of soil aggregate stability with other soil properties as influenced by manure and nitrogen fertilization

Abstract

Soil water-stable aggregate (WSA) stability is one of the most important indicators of soil health, because it influences chemical, biological and other physical properties. At the same time, WSA formation, stabilization and degradation are also some of the most complex processes that occur in the soil, making them difficult to fully understand. In particular, there is a lack of research on WSA stability in the Baltic region. To gain a better understanding how aggregation occurs in Estonian pedo-climatic conditions, this study was conducted in 2014-2015 in a sandy loam Stagnic Luvisol (LV-st) (WRB, 2014). Potato and barley plots were analysed in a three-year crop rotation (potato → spring wheat → barley) with straw removal. The nitrogen (N) fertilization treatments were 0, 40, 80, 120 and 160 kg ha-1 yr-1 N, both without and with 40 Mg ha-1 fermented cattle farmyard manure (FYM) application prior to potato planting in the previous autumn. WSA stability was determined by Eijkelkamp's wet sieving apparatus from air-dried soil samples of less than 2 mm in diameter. The study revealed a negative correlation (r = −0.16) between increased N rates and WSA stability, regardless of FYM applications. Although soil organic carbon (SOC) content increased with additional N fertilization rates, the reduction in soil acidity (pH KCl) levels caused by N fertilization, most likely repealed the positive SOC content effect on WSA stability. In general, compared with sole N fertilization, FYM application had a positive effect on WSA stability. However, even though WSA stability did not always increase with FYM applications, it still had a positive effect on bulk density, SOC content and soil acidity levels. Further research is needed in Estonia due to the complexities involved in the soil aggregation process.

Effects of long-term (70 years) nitrogen fertilization and liming on carbon storage in water-stable aggregates of a semi-arid grassland soil

“…Our soils were acidic and had a moderate proportion of clay and silt, which could also support carbon saturation ( Angers et al., 2011 ). While Are et al. (2018) showed a positive correlation between SOC and aggregate stability, the relationship of SOC with aggregate stability was not significant in this study.…”

“…Long-term application of nitrogen decreased soil pH in 0–10 cm depth by >16%. Ammonium based fertilizers are known to acidify the soil due to nitrification of NH 4 + which releases H+ ions, further reducing the pH of this acidic soil ( Are et al., 2018 ; Bouman et al., 1995 ). The greater acidifying effect of ammonium sulphate than of ammonium nitrate was due to the higher ammonium added in former than the latter at a given application rate.…”

The Effects of Crops Together with Winter Cover Crops on the Content of Soil Water-Stable Aggregates in Organic Farming

“…Furthermore, as the subsoil was located below the plow layer, it was unaffected by direct soil disturbances caused by the tillage, which further increased the contrasts between those soil layers. The high variability of the WSA content over the years was nothing novel, especially on such sandy-textured soils [13,29]. In the current study, those annual variations, besides the coarse soil texture, were most likely caused by the combination of the wetting-drying and freezing-thawing cycles [30], as well as by differences in plant growth, especially in the root development [31], and in the tillage [32].…”

“…Among crops, potato, due to its high tillage requirements, is known to reduce the WSA content [12,13] as a consequence of enhanced mineralization of the soil organic matter [14] as well as by the mechanical disruption of aggregates. The effects of legumes on the WSA content are not unambiguously understood.…”

Effects of Organic Amendments on Soil Aggregate Stability and Microbial Biomass in a Long-Term Fertilization Experiment (IOSDV)

“…IOSDV experiments were set up in 15 different locations in 8 countries following the same principles [45]. Publications on IOSDV experiments mainly concerned changes in crop yields and soil organic matter content [44,[46][47][48], but there are a number of articles which deal with aggregate stability [49,50] or soil microbial biomass [51].…”