Effects of water distribution uniformity on waxy (Zea mays L.) yield: first results

L. Bortolini, M. Martello
2013 Journal of Agricultural Engineering  
In 2050 an increase in water consumption up to 11% and a duplication in food production needs have been predicted (UNESCO-WWAP, 2003) . For this reason the correct choice of irrigation method along with a rational irrigation water management will be essential to increase the water use efficiency. Therefore a reduction in water losses and a utilization of low irrigation volume are needed, integrating the irrigation practice into a sustainable cultivation with a rational water use (Castaldi,
more » ... use (Castaldi, 2009; Bortolini, 2008 ). The irrigation system performance is evaluated in the study area on the basis of adaptability, efficiency and distribution uniformity. The distribution uniformity is a parameter to indicate the irrigation system capability to apply the same application rate to a surface unit for the surface and sprinkler methods, or to discharge the same water volume from each emitters for the microirrigation methods. Without an appropriate uniformity distribution it is impossible to irrigate in a appropriate and efficient manner and with a good water use efficiency. In fact, with a scarce distribution uniformity some zones will be over-watered and other ones will be under-watered Camp, 1997; Lameck, 2011) . The irrigation uniformity can affect the crop yield and influence more or less heavily the environmental impact of the irrigation (Salmeron, 2012). Corn is a very important crop in the North of Italy, especially in the Po Valley Plain where it is cultivated with high water and fertilizer use and often with high energy consumption. The limitation of high crop yield is especially due to an incorrect use both of water and fertilizer elements. For these reasons, it is advisable to use fertigation technique that allows for an optimum use of water and the fertilizers are easily and uniformly distributed near the roots in the correct time and quantities. The proper use of production inputs is an indispensable condition not only for the farm finances but even for the collectivity, and espe-cially for irrigation water, evermore subjected to use limitation and withdrawal restriction, and its efficient use have to involve both engineering aspects of the distribution system and the management strategies of the irrigation operations ( Ghinassi, 2010) . The scope of this work is to quantify the impact of water distribution uniformity of a drip irrigation system on the waxy corn yield and on water use efficiency, by comparing this system with the more traditional sprinkler irrigation system, even on the profitability basis, in order to evaluate its real possible use in the Venetian Plain. Materials and methods The trials were carried out during summer 2012 on the farm of Società Cooperativa Agricola Zootecnica "La Torre" located in Isola della Scala (Verona, Italy), in a drip irrigated plot of 12 ha, subdivided into 3 irrigation zones of 4 ha, and in a gun sprinkler irrigated plot of 1 ha. The soil is a sandy loam (USDA classification), with a good organic matter content. A 30 cm plough was done during autumn burying 42 t ha -1 of cattle slurry, corresponding to about 170 unit of nitrogen. A FAO 600 cultivar was seeded, with a plant spacing of 0.16 m and row spacing of 0.75 m. Fertigation in three different applications was done in the drip irrigated area using N 30 liquid fertilizer, while urea was distributed during hoeing operation in the sprinkler irrigated area, for a total of about 100 unit of nitrogen per ha in each. The waxy corn harvesting was done on the 9 th of August. The drip system was made up of a centrifugal pump with a 37 kW diesel engine, a hydrocyclon and self-cleaning screen filter of 120 mesh, and a Venturi fertigation pump. The drip lines were Aqua-Traxx® PC drip tape of 22 mm of diameter with 1.14 L h -1 of flow rate at 0.8 bar and 20 cm emitter spacing, installed 5 cm underground, located in the furrow and in every other row, supplied by a layflat 5" manifold. The solid-set sprinkler system was made up of a multistage centrifugal pump containing three impellers with a flow rate of 67 m 3 h -1 , a head of 70 m and an engine of 130 kW. The sprinklers were turbine gun sprinklers with a nozzle of 28 mm operating at 5 bar pressure (measured with a Pitot tube) with a flow rate of 1096 L min -1 , positioned with 40 x 40 m spacing and supplied by aluminum pipes of 100 mm of diameter. To define the distribution uniformity of the drip irrigation system the discharge was measured at 24 points within each irrigation zone according to ISO 9261; as the sprinkler system, 100 catch cans were positioned with a grid of 5 m apart, covering an area of 160 m 2 equal to the distance between gun sprinklers and the application rate was measured at each survey point (Figures 1 and 2) . The waxy corn yield was carried out weighing the whole epigeous part of the crops harvested in each survey point for drip system and in 16 points for sprinkler system (all plants of two rows x 1.2 m of length),
doi:10.4081/jae.2013.s2.e162 fatcat:ggx2cvzl3jdwnmqaszf6xubiu4