Phosphorus Budget and Soil Extractable Dynamics in Field Crop Rotations in Mollisols
- Ignacio A. Ciampitti *ab,
- Fernando O. Garcíaa,
- Liliana I. Piconec and
- Gerardo Rubiod
- a International Plant Nutrition Institute, Latin America Southern Cone, Av. Santa Fe 910 (B1641ABO), Acassuso, Buenos Aires, Argentina
b currently at Agronomy Dep., Purdue Univ., 915 W. State St., West Lafayette, IN 47907-2054
c FCA-INTA Balcarce, Mar del Plata National Univ., CC 276, 7620 Balcarce, Buenos Aires, Argentina
d Agricultural College and INBA, Univ. of Buenos Aires, Av. San Martin 4453, C1417DSE, Buenos Aires, Argentina
A better understanding of the P cycle is necessary to provide insights into management strategies that could enhance P bioavailability for crops. Our objectives were to evaluate the effects of continuous P fertilization on (i) the P budget, (ii) soil-extractable P (Pe) dynamics, and (iii) the relationship between these variables. Two crop rotations during a 6-yr period were analyzed in seven on-farm experiments: corn (Zea mays L.)–double cropped wheat (Triticum aestivum)/soybean [Glycine max (L.) Merr.] (C-W/S), and corn–soybean–double cropped wheat/soybean (C-S-W/S). Calculations of net P input considered only P removal (output) and fertilization (input). Initial soil-test P was 13.4 mg P kg−1 (average for the four sites) for the C-W/S rotation and 37.9 mg P kg−1 for the C-S-W/S rotation (average for the three sites). Treatment combinations were two annual rates: unfertilized and grain P removal estimation +10% (average 34 kg P ha−1 yr−1). Not applying P to soils testing 45 to 68 mg kg−1 of initial Pe resulted in a steep Pe decline (slope 0.2 mg kg−1 per unit of negative P budget). Nevertheless, soils with <25 mg kg−1 of initial Pe levels resulted in a very small and gradual decline (slope 0.02 mg kg−1). Use of current P rates applied by local farmers probably results in a small soil-test P buildup with time. The P required to increase Pe by 1 mg P kg−1 was 11 and 8 kg P ha−1 yr−1 for the C-W/S and C-S-W/S rotations, respectively.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © 2011.