Search for: All records

Monitoring soil nitrogen (N) dynamics in agroecosystems is foundational to soil health management and is critical for maximizing crop productivity in contrasting management systems. The newly established soil health indicator, autoclaved‐citrate extractable (ACE) protein, measures an organically bound pool of N. However, the relationship between ACE protein and other N‐related soil health indicators is poorly understood. In this study, ACE protein is investigated in relation to other soil N measures at four timepoints across a single growing season along a 33‐year‐old replicated eight‐system management intensity gradient located in southwest Michigan, USA. On average, polyculture perennial systems that promote soil health had two to four times higher (2–12 g kg⁻¹higher) ACE protein concentrations compared to annual cropping and monoculture perennial systems. In addition, ACE protein fluctuated less than total soil N, NH₄⁺‐N, and NO₃⁻‐N across the growing season, which shows the potential for ACE protein to serve as a reliable indicator of soil health and soil organic N status. Furthermore, ACE protein was positively correlated with total soil N and NH₄⁺‐N and negatively correlated with NO₃⁻‐N at individual sampling timepoints across the management intensity gradient. In addition, ACE protein, measured toward the end of the growing season, showed a consistent and positive trend with yield across different systems. This study highlights the potential for ACE protein as an indicator of sustainable management practices, SOM cycling, and soil health and calls for more studies investigating its relationship with crop productivity.

 

Soil carbon (C) is a major driver of soil health, yet little is known regarding how sensitive measures of soil C shift temporally within a single growing season in response to short-term weather perturbations. Our study aimed to i) Examine how long-term management impacts soil C cycling and stability across a management intensity and plant biodiversity gradient and ii) Assess how sensitive soil health indicators change temporally over the course of a single growing season in response to recent weather patterns. Here we quantify a variety of sensitive soil C measures at four time points across the 2021 growing season at the W.K. Kellogg Biological Station’s Long Term Ecological Research Trial (LTER) located in southwest Michigan, USA. The eight systems sampled included four annual soybean ( Glycine max ) systems that ranged in management intensity (conventional, no-till, reduced input, and biologically-based), two perennial biofuel cropping systems (switchgrass ( Panicum virgatum) and hybrid poplars ( Populus nigra x P.maximowiczii )), and two unmanaged systems (early successional system and a mown but never tilled grassland). We found that unmanaged systems with increased perenniality enhanced mineralizable C (Min C) and permanganate oxidizable C (POXC) values. Additionally, all soil health indicators were found to be sensitive to changes in short-term weather perturbations over the course of the growing season. The implications of this study are threefold. First, this study assess indicators of labile and stable C pools over the course of the growing season and reflects the stability of soil C in different systems. Second, POXC, Min C, and ß-glucosidase (GLU) activity are sensitive soil health indicators that fluctuate temporally, which means that these soil health indicators could help elucidate the impact that weather patterns have on soil C dynamics. Lastly, for effective monitoring of soil C, sampling time and frequency should be considered for a comprehensive understanding of soil C cycling within a system. 

Soil health has received heightened interest because of its association with long‐term agricultural sustainability and ecological benefits, including soil carbon (C) accumulation. We examined the effects of crop diversity and perenniality on soil biological health and assessed impacts on mineralization and C stabilization processes across 10 systems including four no‐till annual row crops, two monoculture perennials, and four polyculture perennials. Crop diversity increased soil biological health in both annual and perennial systems. Rotated annuals with a cover crop increased permanganate oxidizable C (POXC) and soil organic matter relative to continuous corn (Zea maysL.). Perennial polycultures also had 88% and 23% greater mineralizable C relative to the annual and monoculture perennial systems, respectively. All polyculture perennials had significantly greater POXC relative to switchgrass (Panicum virgatumL.) and annual systems, with the exception of restored prairie. Of the systems assessed in this study, incorporating perennial polycultures into rotations is the most effective way to increase soil biological health and enhance C stabilization.

 

Abstract Perennial grain crops are expected to sequester soil carbon (C) and improve soil health due to their large and extensive root systems. To examine the rate of initial soil C accumulation in a perennial grain crop, we compared soil under perennial intermediate wheatgrass (IWG) with that under annual winter wheat 4 years after the crops were first planted. In addition, we tested the effect of three nitrogen (N) sources on C pools: Low available N (Low N (Organic N); 90 kg N ha −1 poultry litter), moderately available N (Mid N; 90 kg N ha −1 urea) and high available N (High N; 135 kg N ha −1 urea). We measured aboveground C (grain + straw), and coarse and fine root C to a depth of 1 m. Particulate organic matter (POM-C), fractionated by size, was used to indicate labile and more stabilized soil C pools. At harvest, IWG had 1.9 times more straw C and up to 15 times more root C compared with wheat. There were no differences in the size of the large (6 mm–250 µm) or medium (250–53 µm) POM-C fractions between wheat and IWG ( P > 0.05) in surface horizons (0–10 cm). Large POM-C under IWG ranged from 3.6 ± 0.3 to 4.0 ± 0.7 g C kg soil −1 across the three N rates, similar to wheat under which large POM-C ranged from 3.6 ± 1.4 to 4.7 ± 0.7 g C kg soil −1 . Averaged across N level, medium POM-C was 11.1 ± 0.8 and 11.3 ± 0.7 g C kg soil −1 for IWG and wheat, respectively. Despite IWG's greater above and belowground biomass (to 70 cm), POM-C fractions in IWG and wheat were similar. Post-hoc power analysis revealed that in order to detect differences in the labile C pool at 0–10 cm with an acceptable power (~80%) a 15% difference would be required between wheat and IWG. This demonstrates that on sandy soils with low cation exchange capacity, perennial IWG will need to be in place for longer than 4 years in order to detect an accumulated soil C difference > 15%.