The efficacy of a novel polyacrylamide spray application method to mitigate soil crusting and enhance seedling emergence on crust susceptible soils

<p>Over 36% of the arable area in England is at moderate to very high risk of surface sealing/crusting and erosion, including much of the better-drained and more easily worked land, especially sandy soils (Evans, 1990).</p><p>The intensive production of leafy greens consists of short growing cycles –between 21 and 28 days- and intensive seedbed preparation. From seeding to emergence, the bare soil is susceptible to rainfall and irrigation induced soil sealing. The direct consequence is an impeded seedling emergence, a delay in stand establishment and reduction in plant populations, with direct impacts on productivity. To avoid soil sealing, the grower is required to undertake additional field operations such as breaking the crust, applying supplementary low intensity irrigations or, in extreme cases, replanting crops, in a vicious cycle that spirals into soil structure degradation, loss of nutrients and further soil-sealing susceptibility.</p><p>Polyacrylamides (PAMs) are long-chained carbon polymers featuring an amide functional group that allows them to form bonds with an array of soil surfaces. The efficacy of PAMs to stabilise soil aggregates and prevent soil splash, capping and erosion has been documented for >25 yrs. Further, it has been demonstrated that PAMs consistently outperform bio-polymers and other synthetic alternatives. However, a technological innovation is required to effectively spray PAM on to the soil surface as typically PAM’s become extremely viscous when mixed with water making conventional spray application un-viable. This research investigates the efficacy of a dual-fluid nozzle to apply PAM to the soil surface. Conventional applications  to mitigate soil sealing are either in powder form or diluted within the sprinkle irrigation system and are effective at application rates ranging from between 10 and 20 kg ha<sup>-1</sup>[SR1] (Levy et al. 1992). However, the powdered form is extremely susceptible to wind drift, and the sprinkle irrigation alternative is severely limited by the amount of water required to deliver the same amount of product.  Initial nozzle calibration results indicate that PAM can be applied at rates of 13-20 kg ha<sup>-1</sup> using 110-150 litres of water ha<sup>-1</sup> instead of 1000 m<sup>3</sup> ha<sup>-1</sup>(Levy et al. 1992). Subsequently, the effect of three PAM formulations with contrasting molecular weight and charge density were tested on a crust susceptible soil. Soil microcosms were subjected to two consecutive simulated rainfall events, representing pre-emergence conditions of field grown leafy salads. Treatment performance was assessed in terms of degree of crust formation. This was quantified by assessing pre and post rainfall changes in Soil Surface Roughness (SSR) using a Creaform HEXAScan laser scanner at 0.20 mm resolution, in infiltration rate using a Decagon Devices minidisk infiltrometer, and in crust penetrative resistance with a 3 mm diameter probe using an Instron 5542 tension and compression testing machine.</p>

Response of Two Potato Varieties to Irrigation Methods in the Dry Mediterranean Area

Due to water scarcity and dry Mediterranean conditions, improving water use efficiency is a major challenge for sustainable crop production and environment protection. Field experiments were conducted for two consecutive years (2010 and 2011) to assess the effects of variety and irrigation method on potato crop, following a 2 × 4 factorial experiment type arranged in a split plot design with two spring potato varieties (Spunta and Marfona), and four irrigation methods (drip irrigation with two modes of dripper spacing/dripper flow: 30 cm at 4 l/h and 60 cm at 8 l/h, sprinkle irrigation, and furrow irrigation), with three replicates. Potato was irrigated when soil moisture in the active root depth was within the range of 75-80% of field capacity as determined by the neutron probe technique. Results did not show any differences between both varieties. Moreover, no differences in marketable yield, total dry matter, and harvest index were found between irrigation methods. However, results showed that sprinkle irrigation significantly enhanced nitrogen use efficiency. Furthermore, both water productivity and irrigation water use efficiency were significantly increased under drip irrigation compared with the other irrigation methods. They were about twice those under furrow irrigation, indicating that the employment of drip irrigation method can effectively address water shortage and sustainable potato production, in the dry Mediterranean region.

Artificial neural network model for simulation of water distribution in sprinkle irrigation

ABSTRACTDetermining uniformity coefficients of sprinkle irrigation systems, in general, depends on field trials, which require time and financial resources. One alternative to reduce time and expense is the use of simulations. The objective of this study was to develop an artificial neural network (ANN) to simulate sprinkler precipitation, using the values of operating pressure, wind speed, wind direction and sprinkler nozzle diameter as the input parameters. Field trials were performed with one sprinkler operating in a grid of 16 x 16, collectors with spacing of 1.5 m and different combinations of nozzles, pressures, and wind conditions. The ANN model showed good results in the simulation of precipitation, with Spearman's correlation coefficient (rs) ranging from 0.92 to 0.97 and Willmott agreement index (d) from 0.950 to 0.991, between the observed and simulated values for ten analysed trials. The ANN model shows promise in the simulation of precipitation in sprinkle irrigation systems.