Mitigation of phosphorus leaching losses via subsurface drains from a cracking marine clay soil

In Scandinavia, subsurface transport via tile drains contributes significantly to phosphorus (P) and nitrogen (N) leaching from arable land, which adds to the eutrophication of surface waters. Using flow-proportional water sampling, various options for mitigating subsurface P leaching losses (and N leaching) were examined in 28 experimental plots on a flat, tile-drained site with 60% marine clay. Two crop rotations and unfertilised fallow were monitored for a total of six years. In addition to topsoil management practices (different forms of tillage, structural liming and mineral P fertilisation), local spatial variations in subsurface transport were determined within the experimental area. Mean total P (TotP) leaching losses after conventional autumn ploughing and inverting the soil to a depth of 23 cm were 0.79 kg ha-1 year-1, with 87% occurring as particulate P (PP), and the corresponding mean total N leaching losses were 27 kg ha-1 year-1, with 91% occurring as nitrate. The coefficient of variation in TotP leaching both in spring before the experiment started (64%) and during the six-year experiment (60%) was higher than the coefficient of variation in P-soil status (20%), or drainage (25%), illustrating the importance of local-scale subsurface transport in this cracking clay. However, TotP and PP leaching losses were significantly (pr>FF <0.001) lower from unfertilised fallow than from other treatments and was not significantly lower after shallow autumn tillage than after conventionally ploughing, whereas PP losses tended to be higher. Infiltration measurements with tension infiltrometers revealed a high variation in saturated hydraulic conductivity within plots. In view of the generally high PP losses, efforts to combat eutrophication of the nearby Baltic Sea should concentrate on soil structure improvements, while extensive tillage and totally omitting P fertilisation of cracking soils with low soil P status appears to be inefficient mitigation options

Structure liming enhances aggregate stability and gives varying crop responses on clayey soils

It has been suggested that liming can improve soil structure and thereby decrease losses of particles and associated nutrients. In this study, two types of structure lime, slaked lime (Ca(OH)(2)) and a mixed product of calcium carbonate (CaCO3) and slaked lime (Ca(OH)(2)), were applied at three different rates in field trials on clayey soils (23%-40% clay). A combination of primary tillage and structure liming was also studied, in a split-plot trial on a clayey soil (25% clay). Aggregate (2-5mm) stability, measured as reduction in turbidity (which is strongly correlated with losses of particulate phosphorus), was significantly increased with the highest application rates of both structure lime products. Aggregate size distribution was also improved with structure lime, creating a finer tilth in the seedbed. Yield response to structure lime was not consistent, with both negative and positive responses over the four-year study period. Positive yield responses can possibly be attributed to the finer tilth preventing evaporation in two dry growing seasons. Negative yield responses were probably an effect of impaired phosphorus availability associated with limited precipitation in May-July in 2011 and 2013. Two years after liming, soil pH levels were significantly elevated in plots with the highest application rate of structure lime, whereas no significant increases were found three years after liming. However, a lingering effect of liming was still detectable, as manganese concentration in barley grain was significantly lower in plots with the highest application rates of both structure lime products in the fourth study year. These results indicate that structure liming can be used as a measure to mitigate phosphorus losses from clayey soils, thereby preventing eutrophication of nearby waters. However, the yield response was varying and unpredictable and thus further investigations are needed to determine the circumstances in which field liming can act efficiently not only to prevent phosphorus losses, but also to ensure consistent yield increases

Long-term evidence for ecological intensification as a pathway to sustainable agriculture

Ecological intensification (EI) could help return agriculture into a 'safe operating space' for humanity. Using a novel application of meta-analysis to data from 30 long-term experiments from Europe and Africa (comprising 25,565 yield records), we investigated how field-scale EI practices interact with each other, and with N fertilizer and tillage, in their effects on long-term crop yields. Here we confirmed that EI practices (specifically, increasing crop diversity and adding fertility crops and organic matter) have generally positive effects on the yield of staple crops. However, we show that EI practices have a largely substitutive interaction with N fertilizer, so that EI practices substantially increase yield at low N fertilizer doses but have minimal or no effect on yield at high N fertilizer doses. EI practices had comparable effects across different tillage intensities, and reducing tillage did not strongly affect yields.Intensifying food production sustainably is critical given growing demand and agriculture's environmental footprint. This meta-analysis finds that practices such as adding organic matter and increasing crop diversity can partly substitute for nitrogen fertilizer to sustain or increase yields

Markfysikaliska studier i långliggande försök med reducerad jordbearbetning

The minimum possible soil tillage is an important part of a sustainable crop production system. Research and practice of reduced tillage was originally started mainly to reduce energy and time consumption related to tillage. However, current research and practice of reduced tillage is also aimed at soil and water conservation as well as reduction of nutrient losses from arable land. Research on reduced tillage in Sweden has been conducted for more than two decades. Reduced tillage comprises different tillage systems, which replace the traditional moldboard ploughing. These also include modem plough shares by which depth of ploughing can be reduced to about 10 cm. This report summarizes investigations of soil physical properties in six long-term experiments with reduced tillage. The experiments were 6 to 24 years old at the time of investigation (in 1997 or 1998). In this study, soil physical properties after minimum tillage and conventional ploughing were compared. Soil physical properties investigated include dry bulk density , soil water content during the vegetation period, infiltration, saturated hydraulic conductivity, water holding capacity, air permeability in the field and laboratory, oxygen content of soil air after continuous or heavy rain, and soil temperature. Soil water content during the vegetation period was measured with TDR (Time Domain Reflectometry). The dry bulk density in the lower part of the top soil was greater in plots with reduced tillage than in plots with conventional ploughing. Many of the investigated soil physical properties were improved by reduced tillage. Variation of soil water content was smaller for reduced tillage than for conventional ploughing. This shows that drainage and water holding capacity often were improved, particularly in the heavy soils. crop yield in heavy clays has been improved by reduced tillage. In some cases, A decrease in yield was observed during the initial periods of reduced tillage, but the difference has been minimized with time, which can be attributed to the improvement of soil structure. This improvement, however, may be less pronounced in light soils. A well planned transition from conventional ploughing to reduced tillage, such as loosening of old plough pan and minimizing of infestation by perennial weeds, can minimize yield losses

Soil and crop responses to controlled traffic farming in reduced tillage and no-till: some experiences from field experiments and on-farm studies in Sweden

The purpose of this study was to investigate the impact of controlled traffic farming (CTF) with respect to soil physical properties and crop yield for Swedish conditions. Three field trials were conducted for six growing seasons in central and southern Sweden. In two of the trials, we compared CTF with random traffic farming (RTF) in deep chiseling (DC, 15-20 cm), shallow cultivation (SC, 5-10 cm) and no-till. The third trial was on farm study by using the existing CTF module at the farm. In the tracks of CTF (traffic zone) dry bulk density was increased and water movement was decreased. Soil penetration resistance was greater in the traffic zone than in the crop zone in some of the trials but the difference was not statistically significant. On average, crop yield was similar between CTF and RTF for all trials. Yield in the traffic zone was significantly less than that in the crop zone in the on-farm trial, but the yield in both zones were similar in the field trial at Lonnstorp, south Sweden. On the contrary, in the field trial at Saby 1 in Uppsala, central Sweden, crop zone produced less yield than traffic zone probably because of too loose soil, which impaired the uptake of nutrients and water. We conclude that if vehicle weight is not very high and the soil is not vulnerable to compaction, dual wheels and CTF are equal options