Nitrogen uptake and N-use efficiency of Mediterranean cotton under varied deficit irrigation and N fertilization |
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| Affiliation: | 1. Soil Ecology and Biotechnology Laboratory, Goulandris Natural History Museum, 13 Levidou Street, 14562 Kifissia, Greece;2. National Agricultural Research Foundation, Institute of Soil Classification and Mapping, 1 Theophrastou Street, 41335 Larissa, Greece;3. USDA-ARS, University of Nebraska, 120 Keim Hall, Lincoln, NE, USA;4. Department of Statistics, University of Nebraska, 340 Hardin Hall, Lincoln, NE 68583-0963, USA;1. Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern Production Technology of Grain Crops, Yangzhou University, Yangzhou 225009, PR China;2. Cotton Research Institute, Chinese Academy of Agriculture Science, Anyang 455000, PR China;3. Texas A&M University, College Station, TX 77843, USA;1. Department of Agriculture and Environment, Instituto de Investigación y Formación Agraria y Pesquera (IFAPA), Córdoba, Spain;2. Department of Agronomy, Institute of Sustainable Agriculture (IAS-CSIC), Córdoba, Spain;3. Efficient Use of Water Program, Institut de Recerca i Tecnologia Agroalimentàries (IRTA), Lleida, Spain;4. Department of Agronomy, University of Córdoba, Córdoba, Spain;1. Technical University of Cartagena (UPCT), Department of Plant Production, Paseo Alfonso XIII, 48, ETSIA, 30203 Cartagena, Murcia, Spain;2. UPCT, Department of Food Engineering, Paseo Alfonso XIII, 48, 30203 Cartagena, Murcia, Spain;1. Faculty of Agriculture, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece;2. School of Land and Food, University of Tasmania, Tas 7001, Hobart, Australia;3. Hellenic Agricultural Organization—“Demeter”, Institute of Industrial and Fodder Plants, 413 35 Larissa, Greece;1. University of California, Davis, Dept. of Plant Sciences, One Shields Ave, Davis, CA 95616-8683, USA;2. University of California, Davis, Dept. of Land, Air and Water Resources, One Shields Ave, Davis, CA 95616-8683, USA;3. University of California Cooperative Extension, 1031 S. Mt. Vernon Ave., Bakersfield, CA 93307, USA |
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| Abstract: | Efficient N management is essential to optimize yields and reduce degradation of the environment, but requires knowledge of deficit irrigation effects on crop yields and crop N outputs. This study assessed the N content and N-use efficiency of cotton over the 2008 and 2009 growing seasons in a single field site of the Thessaly Plain (central Greece). The experiment consisted of nine treatments with three fertilizer rates (60, 110 and 160 kg N ha−1) split into three irrigation levels (approx. 1.0, 0.7 and 0.4 of the amount applied by the producer). Reduced water supply induced a shift in the distribution of N within the plant with seeds becoming an N sink under conditions of water stress. Total crop N increased linearly with irrigation level and reached a maximum average of 261 and 192 kg N ha−1 in 2008 and 2009, respectively. Fertilizer application did not trigger a crop N or yield response and indicated that N inputs were in excess of crop needs. Variation in weather patterns appeared to explain annual differences of nitrate-N in the top soil and N uptake by the crop.The index of lint production efficiency (iNUE) detected crop responses caused by irrigation and annual effects, but failed to account for excessive N inputs due to mineral fertilizer applications. A maximum average iNUE of 9.6 was obtained under deficit irrigation, whereas an iNUE of 8.1 was obtained under 40 cm irrigation when crop N uptake was not excessive (192 kg ha−1 in 2009). In contrast, NUE, as an estimator of N recovery efficiency, identified excessive fertilizer inputs as N losses to the environment and indicated that 60 kg N ha−1 was a rate of high N removal efficiency and long-term N balance. However, NUE failed to account for crop N responses to irrigation and weather/management patterns. In this case study, neither index was able to detect all the factors influencing the N mass balance and both were required in order to provide a comprehensive evaluation of the environmental performance of our cropping system. |
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| Keywords: | Soil nitrates N losses Rainfall Plant fractions Seeds Roots |
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