Subsoiling a compacted soil should loosen it, improve the physical conditions, and increase nutrient availability and crop yields. The aim of this work is to compare the effects of different tillage and fertility treatments in a loamy Typic Hapludoll soil, and to determine the interactions of N fertilization with several soil properties and dryland corn (Zea mays L.) productivity, The experiment, conducted in 1995 and in 1997, had a split-plot design consisting of three tillage systems (MB=moldboard plowing, CH=chisel plowing or NT=no-tillage) in a corn-soybean (Glycine max (L.) Merrill) rotation since 1991 as main treatments. Four subtreatments: (i) subsoil (paratill subsoiler to 40 cm depth in fallow 1995)+N fertilization (100 kg ha(-1) N as ammonium nitrate, at the V6 development stags of corn), (ii) subsoil+no N fertilization, (iii) no subsoiling+N fertilization, and (iv) no subsoiling+no N fertilization. Chemical and physical properties in the top layer of the soils were determined at seeding in 1995. Penetration resistance was measured at seeding, flowering and at harvest in 1995 and at seeding in 1997. Corn shoot dry matter during vegetative stages and grain yield components were also determined. The preparation of seedbed using either moldboard or chisel plowing with or without deep-tillage, increased the vegetative biomass by 27% and the grain yield of the corn crops by 9% over the no-tillage system. Subsoiling no-till plots improved the vegetative growth of the crops, but the effect of the deep-tillage did not modify the corn grain yields. Grain yields were strongly related to the N fertilization treatments. Although bulk density values (BD) ranged between 1.05 and 1.33 Mg m(-3) differences in crop yields were attributed to differences in the ED and the N fertilization. In the western Pampas Region of Argentina, the production of high yielding corn crops, under no water stress conditions, is independent of the tillage systems but negatively related with the soil BD values, and positively dependent on N fertilization.
