Evolution of Smart Strategies and Machines Used for Conservative Management of Herbaceous and Horticultural Crops in the Mediterranean Basin: A Review

Preserving soil quality and increasing soil water availability is an important challenge to ensure food production for a growing global population. As demonstrated by several studies, conservative crop management, combined with soil cover and crop diversification, can significantly reduce soil and water losses. The aim of this review is to evaluate the spread of smart solutions to perform conservation agriculture (CA) well in the Mediterranean Basin, taking into account the evolution of the strategies and the machines used to perform conservative tillage systems in different contexts in the last 30 years, as well as the effects induced by their adoption on the productivity of herbaceous and horticultural crops, weed control and economic feasibility, in comparison with those obtained utilizing conventional techniques based on soil inversion.

Soil Properties after Eight Years of the Use of Strip-Till One-Pass Technology

Tillage is an agrotechnical practice that strongly affects the soil environment. Its effect on soil properties depends on the system and, more specifically, on the degree of soil inversion and loosening. Strip-till is a non-inversive method that loosens only narrow soil strips. In strip-till one-pass (ST-OP) technology, tillage is combined with a simultaneous application of fertilizers and seed sowing. In a static multi-year field experiment, the soil properties after application of ST-OP for 8 years were compared to those of soil under conventional tillage with the use of a moldboard plough to a depth of 20 cm (CT), and equally deep loosened and mixed reduced tillage (RT). A field experiment of these three treatments was performed since 2012 in sandy loam soil, Luvisol. A total of 44 features were examined that described the physical, chemical, biological, and biochemical soil properties in the 0–20 cm layer, and penetration resistance (PR), bulk density (BD), and soil moisture (SM) in the 25–30 cm layer. The influence of the ST-OP technology on the yield of crops was also determined. Multivariate analysis shows that the ST-OP method, in terms of affecting the soil properties, differs considerably from RT and CT treatments. The soil after the ST-OP method contained two- to four-fold more earthworms (En), with a mass (Em) 2- to 5-fold higher, than those in the soil following RT and CT, respectively. In the ST-OP soil the content of available phosphorus (Pa) and available potassium (Ka); the total count of bacteria (Bt), cellulolytic microorganisms (Bc), and fungi (Ff); and the activity of phosphatases (AlP, AcP) were significantly higher. Compared with CT, the content of total organic carbon (Ct) and its content in the fractions of organic matter were also higher, with the exception of humins (CH). The yields of winter rapeseed and winter wheat using the ST-OP technology were marginally higher compared with those using the CT and RT technology.

Germination ecology of dwarf amaranth (Amaranthus macrocarpus): an emerging weed in Australian cotton cropping systems

Dwarf amaranth (Amaranthus macrocarpus Benth.) is a problematic broadleaf weed in many crops in Australia; however, no information is available on the germination ecology of this species. Seeds from two populations of this species were collected from Hillston, NSW, Australia (D-P-01), and Yandilla, QLD, Australia (D-P-02). Seeds were germinated at a range of constant (20 to 45 C) and alternating temperatures (30/20, 35/25, 40/30, and 45/35 C day/night). For the constant temperature treatments, the highest germination occurred at 35 C for D-P-01 (89%) and D-P-02 (82%). Germination was higher at the alternating day/night temperature of 40/30 C for both populations D-P-01 (91%) and D-P-02 (85%). Seed germination of both populations was stimulated by light, which indicates a great amount of emergence of A. macrocarpus can occur on bare ground such as crop seed beds. Results also revealed that this species tolerates a moderate level of salinity and can germinate in slightly alkaline soil conditions. The emergence of this species was highest (47%) for the seed buried at 0.5-cm depth in grey cracking alkaline soil compared with seed buried at the same depth in acidic red soils. These results suggest that soil inversion by tillage to bury weed seeds below their maximum emergence depth could serve as an important tool for managing A. macrocarpus. The results from this study will help in developing more sustainable and effective integrated weed management tactics for the control of this weed and weeds with similar responses in summer cropping systems.

Influence of mechanical site preparation on regeneration success of planted conifers in clearcuts in Fennoscandia – a review

In the Nordic countries Finland, Norway and Sweden, the most common regeneration method is planting after clearcutting and, often, mechanical site preparation (MSP). The main focus of this study is to review quantitative effects that have been reported for the five main MSP methods in terms of survival and growth of manually planted coniferous seedlings of Norway spruce ( (L.) Karst.), Scots pine ( L.) and lodgepole pine ( var. Engelm.) in clearcuts in these three countries. Meta analyses are used to compare the effects of MSP methods to control areas where there was no MSP and identify any relationships with temperature sum and number of years after planting. In addition, the area of disturbed soil surface and the emergence of naturally regenerated seedlings are evaluated. The MSP methods considered are patch scarification, disc trenching, mounding, soil inversion and ploughing. Studies performed at sites with predominately mineral soils (with an organic topsoil no thicker than 0.30 m), in boreal, nemo-boreal and nemoral vegetation zones in the three Fenno-Scandinavian countries are included in the review. Data from 26 experimental and five survey studies in total were compiled and evaluated. The results show that survival rates of planted conifers at sites where seedlings are not strongly affected by pine weevil ( L.) are generally 80–90% after MSP, and 15–20 percent units higher than after planting in non-prepared sites. The experimental data indicated that soil inversion and potentially ploughing (few studies) give marginally greater rates than the other methods in this respect. The effects of MSP on survival seem to be independent of the temperature sum. Below 800 degree days, however, the reported survival rates are more variable. MSP generally results in trees 10–25% taller 10–15 years after planting compared to no MSP. The strength of the growth effect appears to be inversely related to the temperature sum. The compiled data may assist in the design, evaluation and comparison of possible regeneration chains, i.e. analyses of the efficiency and cost-effectiveness of multiple combinations of reforestation measures.Picea abiesPinus sylvestrisPinus contortalatifoliaHylobius abietis

Investigating the Influence of Biochar Particle Size and Depth of Placement on Nitrous Oxide (N2O) Emissions from Simulated Urine Patches

The use of biochar reduces nitrous oxide (N2O) emissions from soils under specific conditions yet the mechanisms through which interactions occur are not fully understood. The objectives of this glasshouse study were to investigate the effect of (i) biochar particle size, and (ii) the impact of soil inversion—through simulated mouldboard ploughing—on N2O emissions from soils to which cattle urine was applied. Pine biochar (550 °C) with two different particle sizes (<2 mm and >4 mm) was mixed either into the top soil layer at the original 0–10 cm depth in the soil column or at 10–20 cm depth by inverting the top soil to simulate ploughing. Nitrous oxide emissions were monitored for every two to three days, up to seven weeks during the summer trial and measurements were repeated during the autumn trial. We found that the use of large particle size biochar in the inverted soil had significant impact on increasing the cumulative N2O emissions in autumn trial, possibly through changes in the water hydraulic conductivity of the soil column and increased water retention at the boundary between soil layers. This study thus highlights the importance of the role of biochar particle size and the method of biochar placement on soil physical properties and the implications of these on N2O emissions.

Yellow bristle grass (Setaria pumila) germination biology

The presence of Setaria pumila in dairy pastures lowers feed quality and may cause grazing avoidance. More information is required about the germination biology of this weed to improve the effectiveness of control strategies. Base temperature and germination profile were determined on a thermo-gradient table. For emergence depth, seeds were buried at 0—50 mm and time to emerge recorded. Seed persistence was tracked at seven field sites over 5 years and in a laboratory-based controlled-ageing test. Base temperature for germination was 10.2˚C, germination was most rapid at 30—35˚C and most numerous from 20—30˚C. Emergence occurred from 2—50 mm depth but mostly from 2—15 mm. The controlled-ageing test indicated the seed was viable for <3 years. However, some Setaria pumila seed continued to germinate after 5 years of burial in all but the clay soil. Farmers should try to prevent this species from seeding for at least 5 years to reduce the seed bank. Soil inversion could promote dormancy and seed persistence. If followed by effective control, cultivation could stimulate germination and further reduce the seed bank.

Evidence for soil carbon enhancement through deeper mouldboard ploughing at pasture renovation on a Typic Fragiaqualf

Permanent pastures require periodic renewal (cultivation and resowing) to maintain their productive potential, which involves a short-term carbon (C) loss. Normal cultivation (ploughing or discing) often involves only the top 10–15 cm, or less, of pasture soils. A regrassing field trial with ryegrass plus white clover swards was established in 2011 to assess the effect of deeper ploughing (25 cm) on C storage in an imperfectly drained soil (Tokomaru silt loam). The site was core sampled (0–30 cm depth) 2 and 4 years (i.e. in 2013 and 2015 respectively) after cultivation and regrassing (soil inversion treatment) to assess changes in soil C content at different depths. At both times, an adjacent uncultivated ryegrass paddock (undisturbed pasture treatment) under similar grazing intensity was also sampled and C stocks were compared. Profiles of cultivated soils (soil inversion) showed higher (P < 0.01) C stocks than the adjacent permanent pasture at the nominal 15–25 and 25–30 cm depths and significantly lower (P < 0.01) C stocks in the topsoil (nominal 0–5 cm depth) for both years sampled (2013, 2015). These findings imply that the differences (inversion – pasture) were consistent 4 years after cultivation and deep ploughing at pasture renewal had resulted in an overall increase in soil C mass to approximately 30 cm of ~18% (13.9 Mg C ha–1; equivalent soil mass 3701 Mg soil ha–1) compared with not undertaking the regrassing. This gain in soil C may be temporary, but in a period of 4 years it has significantly increased the net residence time of C in soil related to soil inversion.