Decimetric-scale two-dimensional distribution of soil phosphorus after 20 years of tillage management and maintenance phosphorus fertilization
Cambouris, A.N., Messiga, A.J., Ziadi, N., Perron, I., Morel, C. (2017). Decimetric-scale two-dimensional distribution of soil phosphorus after 20 years of tillage management and maintenance phosphorus fertilization, 81(6), 1606-1614. http://dx.doi.org/10.2136/sssaj2017.03.0101
© Soil Science Society of America. Improving soil test P assessment at plot scale is essential for productivity in conservation agriculture systems. We characterized the distribution of Mehlich-3 P (PM3) concentrations at the decimetric scale with depth on either side of the sowing row in no-till (NT) and moldboard plow (MP) plots fertilized with 35 kg P ha-1 every 2-yr in a corn-soybean rotation (20-yr). A total of 996 soil samples (83 samples × 2 depths [0-5 and 5-20 cm] × 6 plots [3 blocks each MP and NT]) were collected at corn harvest in 2012. The average PM3 concentrations in the 0- to 5-cm layer were 35.7 and 63.4 mg kg-1 in MP and NT, respectively. The PM3 concentration in the 5- to 20-cm depth was similar between MP and NT and averaged 32.0 mg kg-1. The horizontal distribution of PM3 concentrations in these plots was less sensitive to extrinsic factors including tillage, P fertilization and soil depth. High coefficients of variation were associated with PM3 data in both MP (77 and 63% at 0-5 and 5-20 cm, respectively) and NT plots (46 and 66% at 0-5 and 5-20 cm, respectively). It is possible that this strong overall variability overshadowed any PM3 pattern that could have been introduced by NT management. Geostatistical semivariance analysis indicated a predominance of random spatial dependence in most plots, except two plots (one MP and one NT) with moderate spatial structures. The 2-D geospatial model related to tillage was not detected by the sampling grid used at this experimental site. Therefore, a similar sampling strategy would be appropriate and could be recommended for these two tillage systems in this long-term corn-soybean rotation.
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