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Fluid Journal : Summer 2016
22 The Fluid Journal Summer 2016 ▼ DOWNLOAD Table 1. Analysis of variance regarding source, rate, and locality of application of N for gross yield (GY) and industrial characteristics1. Control treatments were disregarded in this analysis. Cause of variation GY TRS TPH TSH ton/ha kg/ha ton/ha Source UAN 81.72a 126.74a 10.34a 10.36a AN 81.14a 125.71ab 10.14a 10.17a Urea 74.38b 119.30b 8.81b 8.91b Rate 60 78.35 123.80 9.68 9.74 120 80.50 123.72 9.92 9.97 180 78.39 124.23 9.68 9.73 Locality In furrow 79.24 123.03 9.71 9.76 Surface 78.92 124.81 9.82 9.87 CV(%) 11.79 7.56 15.35 14.76 Mean 79.08 123.92 9.76 9.81 1 Industrial characteristic: total recoverable sugar (TRS), total POL per hectare (TPH), and total sugar per hectare (TSH). Means followed by the same letters do not differ (Duncan P>0.05). and available K, Ca, Mg 76, 1.8, 34, and 15 mmolc/dm3,respectively, and BS 67%. Field. A three-year-old sugarcane field was used to set up the study after harvest in May 2014. Results Response. Table 1 presents the results for gross yield and industrial characteristics of sugarcane in response to treatments applied. Nitrogen source affected all parameters evaluated, while rate and locality of application did not affect anyone. For every parameter, UAN and AN presented a similar performance and were superior to Urea. Exception was made to the amount of total recoverable sugar (TRS) while AN performed similarly to UAN and Urea, although UAN Was superior to Urea. Effectiveness. Table 2 presents the relative agronomic effectiveness (RAE) of N sources for gross yield. Under in- furrow application of sources, UAN and AN presented a similar RAE of 108%, when compared to Urea. Considering the surface application, UAN and AN were 112% and 110%, respectively, more efficient when compared to Urea. Gross yield. Figure 1 presents the gross yield response to rates and sources of N, regarding the locality of application. Quadratic models were adjusted to UAN and AN, while a linear model was adjusted to Urea for both localities of application. Gross yield with UAN and AN application were, respectively, 12% and 14% higher as compared to Urea at the rate of 60 kg N/ ha. At the recommended rate (120kg N/ha), UAN and AN produced, respectively, 10% and 12% more gross yield as compared to Urea. Discussion Vitti et al. (2007) studied N fertilizers (urea, AP, AN and UAN) at a single rate (70 kg N/ ha), submitted to two places of application (broadcast vs. strip), and observed no effect on yield caused by the locality of the fertilizer application. Authors observed that N losses due to volatilization with urea and UAN decreased gross yield significantly as well. In another study, Costa et al. (2003) also found yield decrease to be related to N losses due to volatilization. The absence of yield response to N rates and places of application may be attributed to dry weather conditions during the period of the trial, as well as due to partial supply of N coming from residue decomposing from previous seasons. Summing up Nitrogen application is a key practice for Table 2. Relative agronomic effectiveness (RAE) of N sources† for gross yield of sugarcane, regarding the locality of application, in the state of São Paulo, Brazil. Source RAE (%) In furrow Surface Urea 100 100 UAN 108 112 AN 108 110 † Considering all N rates applied for each source. ‡ No nitrogen applied. high sugarcane yields, but the right source must be selected in order to avoid losses under certain soil and climate conditions. Under the agronomic conditions of this study, UAN and AN showed to be more effective than Urea, disregarding if it is applied in furrow or to the soil surface. Soil surface application of fertilizer tends to be cheaper and easier for farmers, being a great advantage for sources like UAN and AN. Figure 1. Gross yield of sugarcane in response to sources, rates and locality of application N in the state of São Paulo, Brazil. Dr. Eros Franscisco is Brazil Program Deputy Director, Dr. Fabio Dias and Dr. Raffaella Rossetto are researchers at Sao Paulo Agribusiness and Technology Agency, Dr. Yebin Zhao is an Agronomist at CF Industries, and Dr. Luis Prochnow is Brazil Program Director at IPNI in Brazil.