A simple tile drainage model was incorporated into a recent version of the CROPGRO-soybean model. The model was calibrated and validated using four years of data from the Water Quality Research site, located at the Iowa State University Northeast-Research Center near Nashua, Iowa having two soil types (Readlyn and Kenyon). The data consisted of measurements of soil water contents at different depths and times, cumulative monthly tile flow, and final crop yield from 36 different 0.41 ha plots that were individually tile drained. The model was calibrated to give the best fit between the predicted and measured tile flow, soil water content, and crop yield from 1993 and 1994 for each soil type. It was validated by using data from 1995 and 1996 for each soil type. Predicted soil water contents, tile drainage and soybean yield matched measured values very well over all years for these two soil types. The results of this study show that the modified CROPGRO model does a very good job in simulating soybean yields and water dynamics for Readlyn and Kenyon soil in the experiment.Agricultural Science | Agriculture | Agronomy and Crop Sciences | Bioresource and Agricultural Engineering | Forest Management | Water Resource Management Comments ABSTRACT. A simple tile drainage model was incorporated into a recent version of the CROPGRO-soybean model. The model was calibrated and validated using four years of data from the Water Quality Research site, located at the Iowa State University Northeast-Research Center near Nashua, Iowa having two soil types (Readlyn and Kenyon). The data consisted of measurements of soil water contents at different depths and times, cumulative monthly tile flow, and final crop yield from 36 different 0.41 ha plots that were individually tile drained. The model was calibrated to give the best fit between the predicted and measured tile flow, soil water content, and crop yield from 1993 and 1994 for each soil type. It was validated by using data from 1995 and 1996 for each soil type. Predicted soil water contents, tile drainage and soybean yield matched measured values very well over all years for these two soil types. The results of this study show that the modified CROPGRO model does a very good job in simulating soybean yields and water dynamics for Readlyn and Kenyon soil in the experiment.
The available contents of microelements in the topsoil can influence the yield and quality of flue-cured tobacco. Xuancheng is the dominant tobacco-planting region in Anhui province since 2008. In this paper, the topsoil available Fe, Mn, Cu and Zn contents of 4197 farmlands mainly under rice-rice rotation and wheat-rice rotation in 2008 and of 124 typical farmlands under tobacco-rice rotation in 2015 in Xuancheng city were analyzed in order to disclose the changes and spatial distributions of these microelements and to instruct the reasonable application of the microelement fertilizers. The results showed that the topsoil average available contents in the farmlands under rice-rice rotation or wheat-rice rotation in 2008 were 105.9 mg•kg −1 for Fe, 19.6 mg•kg −1 for Mn, 4.5 mg•kg −1 for Cu, and 3.0 mg•kg −1 for Zn, respectively, increased by 33.14%, 64.29%, 51.11% and 36.67%, respectively, compared with those in the 2 nd Soil Survey in 1980s, and the historic, once intensive and overall application of microelement fertilizers was attributed to the great increases. The topsoil average available contents in the farmlands under tobacco-rice rotation in 2015 were 31.1 mg•kg −1 for Fe, 9.8 mg•kg −1 for Mn, 2.1 mg•kg −1 for Cu, and 0.3 mg•kg −1 for Zn, respectively, decreased by 70.63%, 50.00%, 53.33% and 90.00%, respectively, compared with those of the farmlands under rice-rice rotation or wheat-rice rotation in 2008, and the net deficiencies in the input and output of microelements were attributed to the significant decreases in the topsoil microelements. It is necessary to monitor the farmlands under tobacco-rice rotation dynamically and in time in order to decide whether applying microelement fertilizers or not.
pH, exchangeable Ca 2+ and Mg 2+ of soil can influence the yield and quality of flue-cured tobacco. Xuancheng city is the dominant tobacco-planting region in Anhui province since 2008. A general soil survey was conducted in Xuancheng city to understand the current situations of pH, exchangeable Ca 2+ and Mg 2+ of farmlands under tobacco-rice rotation and to decide whether continuous applying dolomite powders to abate soil acidification. In total 124 topsoil samples (0 -20 cm) were collected from the typical farmlands and soil pH, exchangeable Ca 2+ and Mg 2+ were measured. The results showed that soil pH and Ca 2+ and Mg 2+ in Xuancheng city were generally in the suitable grades, pH ranged from 4.56 to 8.42 with an average of 5.87, exchangeable Ca 2+ ranged from 1.01 cmol(1/2Ca 2+ ) kg −1 to 100.55 cmol(1/2Ca 2+ ) kg −1 with an average of 11.07 cmol(1/2Ca 2+ ) kg −1 , and exchangeable Mg 2+ ranged from 0.14 cmol(1/2Mg 2+ ) kg −1 to 2.86 cmol(1/2Mg 2+ ) kg −1 with an average of 0.81 cmol(1/2Mg 2+ ) kg −1 , all spanned from the low grades to the high grades. To the whole Xuancheng city, 37.10%, 62.10% and 72.58% of the surveyed farmlands were in the low grades of pH, exchangeable Ca 2+ and Mg 2+ , respectively, while 52.42%, 25.00% and 20.97% of the farmlands were in the suitable grades, respectively. pH had an extremely significantly positive Napierian logarithm correlation with exchangeable Ca 2+ and an extremely significantly positive power correlation with exchangeable Mg 2+ . In total about 338.2 kg•hm −2 of Ca 2+ and 202.4 kg•hm −2 of Mg 2+ are annually input into the farmlands, while about 110.4 kg•hm −2 of Ca 2+ and 7.4 kg•hm −2 of Mg 2+ are annually moved out from the farmlands, exchangeable Ca 2+ and Mg 2+ were annually increased by 225.2 kg•hm −2 and 187.6 kg•hm −2 in the farmlands, respectively. It
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