Background and aims: Organic fertilizers and cover crops (CC) are considered crucial strategies to pursue the objective of increasing soil organic carbon (SOC). The present research focuses on an ‘on farm experimentation’ to assess the combined effects of organic fertilization with different biomasses, CC and irrigation on SOC stock. Methods: A 4-year on-farm experimentation was co-developed with local farmers and a land reclamation authority in north-eastern Italy on a biennial maize-soybean rotation. We examined the effects of two organic fertilizers (compost or digestate), three CC treatments (a fixed cover crop species – x triticosecale; a succession of cover crop species – Sinapis alba and Lolium multiflorum; no CC) under rainfed and irrigated conditions on the SOC content and stock, and crops yields. Results: All these integrated practices – except when digestate was applied in the field in the absence of a CC under rainfed conditions – determined a significant increase of the SOC stock after 4 years, matching the goals set by the ‘4 per mille’ initiative. The highest SOC increase was observed under irrigated management and compost fertilization, regardless of the presence or absence of a CC (range: 9.3–10.3 Mg ha⁻¹ in the first 0–40 cm of soil). Soybean grain yields were comparable with those obtained in farms of the same rural district under business as usual, but maize grain yields were lower. Conclusion: SOC accumulation is achievable in the short term with abundant applications of organic biomass, but the strategy might lead to economic loss such as lower maize productivity.

Cover crops (CCs) can affect the cropping systems’ N dynamics and soil water content (SWC), but optimizing their potential effects requires knowledge of their growth pattern, N accumulation, and mineralization. For this purpose, a 3-year field experiment was initiated in northeast Italy involving a maize-soybean rotation. The objectives of this study were to (i) evaluate the use of time series vegetation indices (VIs) obtained from the Sentinel-2 satellite for monitoring the growth of CCs and estimating their biomass and N uptake at termination; (ii) investigate the effects of different CCs on cash crop yield and SWC; and (iii) use the simulation model CC-NCALC to predict the nitrogen contribution of CCs to subsequent cash crops. Three CC systems were tested: a fixed treatment with triticale; a 3-year succession of rye, crimson clover, and mustard; and a control with no CCs. Satellite imagery revealed that rye and triticale grew faster during the winter season than clover but slower compared to mustard, which suffered a frost winterkilling. Both grasses and mustard produced greater biomass at termination compared to clover, but none of the CC species affected SWC or yield and N uptake of the cash crop. A net N mineralization of all the CC residues was estimated by the model (except for the N immobilization after triticale roots residues). During the subsequent cash crop season, the estimated clover and mustard N released was around 33%, and the triticale around 3% of their total N uptake, with a release peak 2 months after their termination. The use of remote sensing imagery and a prediction model of CC residue decomposition showed potential to be used as instruments for optimizing the CCs utilization and enhancing cropping water and N fertilization management efficiency; however, it must be further analyzed with other CCs species, environmental conditions, and cropping systems.

Agricultural management affects soil fertility through the frequency and type of agronomic practices such as mechanical operations, type and rate of fertilizers, crop rotations, and residue management. This study evaluated the evolution of soil chemical properties (pH; electrical conductivity; soil organic carbon, SOC; total Kjeldahl nitrogen, TKN; and available phosphorous, PO4-P) over time in two farming systems, organically and conventionally managed, after 5 and 14 years after the establishment of both systems, in northeastern Italy. SOC content remained stable in the conventional farming system, but slightly decreased in the organic farming system, despite inputs from organic amendments. In contrast, soil TKN remained consistently higher in the organic farming system. The PO4-P increased over time, in both farming systems. Moreover, we observed that an increase of 1% in soil clay content resulted in increases of 0.0534 and 0.0053 g kg–1 in SOC and TKN, respectively. In conclusion, our results indicate that organic management does not have an advantage over conventional management in terms of soil organic matter accumulation. Highlights - Organic management did not increase soil organic carbon content 14 years after the system was established. - The soil organic carbon was stable over time in the conventional system. - Soil organic nitrogen was higher in the organic farm than in the conventional farm. - Soil C/N ratios in organic and conventional management were <10, indicating active mineralization.

This study aimed to assess whether hemp (Cannabis sativa L.) behaves as a Cr(III)-tolerant or a hyperaccumulator species and whether it could be a suitable species for the phytomanagement of Cr(III)-contaminated soils. The experiment was conducted in pots under greenhouse conditions comparing two fiber hemp (Fibranova and Carmagnola) and two seed hemp (Futura 75 and Fedora 17) varieties under four different soil Cr levels (24.3, 40.1, 55.8, and 87.4 mg kg⁻¹) supplied with tannery sludge. The Cr level did not significantly influence hemp biomass production or Cr accumulation in the aboveground biomass. Focusing on marketable fractions, Cr uptake was 0.03 ± 0.04 mg plant⁻¹ in the stems of fiber varieties and 0.60 ± 0.17 mg plant⁻¹ in the seeds of seed varieties. The only significant accumulation of Cr content was indeed observed in the root system, where it reached 0.63 mg plant⁻¹ for the fiber varieties and 1.76 mg plant⁻¹ for the seed varieties in the fertilization with 200% N by tannery sludge (T200) treatment. The Cr translocation factor (aboveground-to-belowground biomass) decreased from 2.17 to 0.37, increasing the Cr level applied from 24.3 to 87.4 µg g⁻¹. The maximum Cr concentrations in aboveground biomass fractions (average value of 40.4 mg kg⁻¹) were found in the seeds, regardless of treatment. The low Cr content in the aboveground biomass suggests that hemp can be considered an excluder species, valid as a candidate for Cr-contaminated soils’ phytomanagement.

Nocturnal transpiration (E) can reduce water productivity by causing water loss during a period without photosynthetic activity. This study quantifies tomato nocturnal E under greenhouse conditions, comparing two irrigation managements (full irrigation – FI vs. Deficit irrigation – DI) and four fertilization treatments (raw compost vs. sieved compost vs. mineral vs. no fertilization), addressing a key gap in understanding potential inefficiencies in crop water use. Physiological and environmental parameters were monitored weekly from transplanting to harvesting at four different hours each day (06:00, 12:00, 18:00, and 24:00). At harvest, fruit yield, quality, and water productivity were assessed. Only irrigation significantly affected E, with FI plants exhibiting higher daytime E rates (+11–16%) than DI. Stomatal conductance varied by time but was not influenced by irrigation. Nocturnal E persisted at ~12–13% of daytime rates, indicating residual stomatal opening. Under FI, E positively correlated with leaf temperature and vapor pressure deficit, while under DI, E was more influenced by environmental temperature, reflecting tighter environmental control under water stress. Neither irrigation nor fertilization significantly affected total (on average 64.1 Mg ha⁻¹) or marketable fruit yield (about 77.5% of total yield). Water productivity was significantly higher under DI (+14.7%) than FI (21.5 kg m⁻³). DI also increased fruit dry matter content (+6.5%) and slightly lowered fruit pH without affecting total soluble solids, titratable acidity, or electrical conductivity.