Crop yield response to water - Cra

Table 3 Sample calculation of monthly water budget for irrigation scheduling in a high density (510tree/ha), 5-year-old olive orchard grown in a loam soil at Venturina (central Italy). Two levels(full, deficit) of irrigation are reported yearly ET o = 965 mm; precipitation 708 mm. Floweringoccurred on 13 May 2007. The crop coefficient was 0.55, the coefficient of ground cover 0.8.Average monthly min and max temperatures and ET o are reported. Effective rainfall (ERain)was calculated as 70 percent of total rainfall (Rain), excluding precipitations less than 4 mm.(Caruso et al., 2011)Month T max (°C) T min (°C)ET o(mm/day)ET c(mm/month)Rain(mm/month)ERain(mm/month)ET c - ERain(mm/month)Fullirrigation(mm/month)Deficitirrigation(mm/month)J 14.7 5.5 0.7 9.6 30 21 -11.4F 15.6 4.6 1 12.3 96.6 67.62 -55.32M 16.4 5.3 1.9 25.9 76.6 53.62 -27.72A 22.3 6.9 3.3 43.6 6.8 4.76 38.84 2.8 2.8M 24.2 10.6 4.3 58.7 130.8 91.56 -32.86 2.8 2.8J 27 14 4.8 63.4 68.8 48.16 15.24 3.9 3.9J 30.3 14.6 5.4 73.7 0.6 0.42 73.28 58.9 19.7A 29.8 12.9 4.3 58.7 36.2 25.34 33.36 36 13S 26.7 10.2 2.8 37 19 13.3 23.7 30.4 30.4O 22.5 7.9 1.5 20.5 88 61.6 -41.1N 16.8 4.7 0.9 11.9 102.6 71.82 -59.92D 18.1 -1.6 0.7 9.24 52.2 36.54 -27.3the water supply is normally adequate to meet the full ET needs, but as the summer starts andthe ET o increases, supply from the drip system is insufficient and water is extracted from thesoil reservoir to meet the demand.As the season progresses, water deficits set in, to increase in severity as the summer advances,but by the end of summer ET o start to decline and the rains may arrive. At this time, the levelof stress is reduced or eliminated, which is desirable during the fruit growth and maturationperiod. By manipulating irrigation frequency, the grower can run the system a fixed time(normally at its maximum capacity) and scheduling becomes straightforward. The RDI 2approach permits the installation of irrigation systems designed to cope with situations ofvery limited water allocation, for instance in cases when water is drastically restricted duringmidsummer (mid-July, end of August) for conflicting urban uses (e.g. tourism in Liguria, Italy).A key factor for success with the RDI 2 approach is to start irrigating early enough to conservethe soil water reserve for when the ET o demand is high.The sustained deficit irrigation strategy (SDI) is planned by distributing the water deficitproportionally to the monthly ET requirements. In this case, for the same amount of water,the anticipated water deficits are of less magnitude at midsummer than in RDI 1 , while thestress that develops earlier and later in SDI, should be of greater magnitude than in the RDI 1 .310crop yield response to water