Effect of contrasting crop rotation systems on soil chemical, biochemical properties and plant root growth in organic farming: first results

Abstract

Organic farming is claimed to improve soil fertility. Nonetheless, among organic practices, net C-inputs may largely vary in amount and composition and produce different soil conditions for microbial activity and plant-root system adaptation and development. In this study, we hypothesised that, in the regime of organic agriculture, soil chemical and biochemical properties can substantially differ under contrasting crop rotation systems and produce conditions of soil fertility to which the plant responds through diverse growth and production. The impact of 13 years of Alfalfa-Crop rotation (P-C) and Annual Crop rotation (A-C) was evaluated on the build up of soil organic carbon (SOC), active (light fraction organic matter, LFOM; water soluble organic carbon, WSOC) and humic fraction (fulvic acids carbon, FAC; humic acids carbon, HAC), soil biochemical properties (microbial biomass carbon, MBC; basal respiration, dBR; alkaline phosphatase AmP; arylsulfatase ArS; orto-diphenoloxidase, o-DPO) and the amount of available macro-nutrients (N, P, and S) at two different soil depths (0-10 cm and 10-30 cm) before and after cultivation of wheat. We also studied the response of root morphology, physiology and yield of the plant-root system of wheat. Results showed that the level of soil fertility and plant-root system behaviour substantially differed under the two crop rotation systems investigated here. We observed high efficiency of the P-C soil in the build up of soil organic carbon, as it was 2.9 times higher than that measured in the A-C soil. With the exception of o-DPO, P-C soil always showed a higher level of AmP and ArS activity and an initial lower amount of available P and S. The P-C soil showed higher rootability and promoted thinner roots and higher root density. In the P-C soil conditions, the photosynthesis and yield of durum wheat were also favoured. Finally, cultivation of wheat caused an overall depletion of the accrued fertility of soil, mainly evident in the P-C soil, which maintained a residual higher level of all the chemical and biochemical properties tested.

Seasonal Soil Respiration Dynamics and Carbon-Stock Variations in Mountain Permanent Grasslands Compared to Arable Lands

“…The reasons behind the soil C depletion are not ascribable to microbial activities, as the heterotrophic soil respiration showed no differences between grassland, lentil and emmer (Figure 4). Nevertheless, similarly to other studies, the conversion of permanent grassland to cropland has indeed been shown to lead to decreased soil C stock [4,11]. The debate on the effects of water soil erosion on the soil C sink/source is still open, as diametrically opposing data emerge from the recent literature (e.g., [23]).…”

“…Enhancement of the soil C stock is considered a virtuous practice at the global scale, and there is wide agreement that conversion from arable land to grassland leads to soil C stock increases [4,13,29,35]. However, some recent studies have suggested that a change in short-term land use from permanent grassland (i.e., of >30 years) to arable lands (e.g., 2 years of corn) followed by a return to grassland can actually increase the soil C stock [15], although other studies have suggested that the light fraction of the organic matter of grasslands might be lost soon after the tillage [11].…”

“…Grasslands are considered to be pivotal for biodiversity conservation, and they also have a significant role in greenhouse gas emission, as they have potential to mitigate global warming [8]. For these reasons, it has become crucial to study the effects of human activities on C stored in terrestrial ecosystems [11], and particularly for soil heterotrophic respiration, which is strongly related to soil organic C decomposition [12,13]. Due to low soil temperatures, soil organic matter in mountain temperate grasslands tends to decompose at low rates [14], although management practices such as soil tillage might have relevant roles on the soil C cycling because of their influence on soil aggregate turnover, aeration, erosion, infiltration and water-holding capacity [15].…”

Short-Term Effects of Changing Soil Management Practices on Soil Quality Indicators and Crop Yields in Greenhouses

“…Although total organic carbon is the most widely used indicator to assess soil quality, soil productivity and agricultural sustainability [24,25], it is generally accepted that the change in its content is not very sensitive in the short and medium term [26,27], so labile fractions-which often include particulate organic carbon (POC), light fraction (LF), and water-soluble organic carbon (WSOC) [28]-have been used as short-term indicators after changing soil management practices [29][30][31][32][33][34]. POC, LF and WSOC are three fractions considered active in the nutrient cycles, readily available for microbial breakdown and closely associated with nutrient supply to crops [35,36].…”

Wheat yield as a measure of the residual fertility after 20 years of forage cropping systems with different manure management in Northern Italy

“…Crop rotations can also affect soil fertility and, hence, crop yields (Berzsenyi et al, 2000). Inclusion of legume leys in rotations increases the N supply (Riedell et al, 2009) as it is expected from N-fixing species, while enhancing other biochemical and physical aspects of soil fertility (Monaci et al, 2017).…”