Effect of deep-tillage and nitrogen fertilization interactions on dryland corn (Zea mays L.) productivity

Subsoiling a compacted soil should loosen it, improve the physical conditio ns, and increase nutrient availability and crop yields. The aim of this wor k is to compare the effects of different tillage and fertility treatments i n a loamy Typic Hapludoll soil, and to determine the interactions of N fert ilization with several soil properties and dryland corn (Zea mays L.) produ ctivity, The experiment, conducted in 1995 and in 1997, had a split-plot de sign consisting of three tillage systems (MB=moldboard plowing, CH=chisel p lowing or NT=no-tillage) in a corn-soybean (Glycine max (L.) Merrill) rotat ion since 1991 as main treatments. Four subtreatments: (i) subsoil (paratil l 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 subsoili ng+no N fertilization. Chemical and physical properties in the top layer of the soils were determined at seeding in 1995. Penetration resistance was m easured 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 biom ass 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 crop s, but the effect of the deep-tillage did not modify the corn grain yields. Grain yields were strongly related to the N fertilization treatments. Alth ough bulk density values (BD) ranged between 1.05 and 1.33 Mg m(-3) differe nces in crop yields were attributed to differences in the ED and the N fert ilization. In the western Pampas Region of Argentina, the production of hig h yielding corn crops, under no water stress conditions, is independent of the tillage systems but negatively related with the soil BD values, and pos itively dependent on N fertilization. (C) 2000 Elsevier Science B.V. All ri ghts reserved.