Long-term cropping effects on maize: crop evapotranspiration and grain yield

CÁRCOVA, J., MADDONNI, G. A. AND GHERSA, C. M

AGRONOMY JOURNAL

AMER SOC AGRONOMY

Año: 2000 vol. 92 p. 1256 - 1265

0002-1962

Long-term cropping in the Rolling Pampa of Argentina may reduce available soil water for maize (Zea mays. L) production. Grain yield, however, has not decreased possibly because of genetic improvement of maize hybrids. Our objectives were to: (i) evaluate root and shoot growth and its relation to crop evapotranspiration (ETa), (ii) analyze interactions among hybrids and length of the cropping period on grain yield and its components and (iii) establish functional relations between grain yield components and their determinant processes. Three hybrids with contrasting production stability coefficients and representing different eras of maize breeding were grown at three farms in 1994/95 and 1995/96 in fields with short (S) and long (L) cropping periods on silty clay loam soils (fine, illitic, thermic, Typic Argidolls). Silking took place 5 to 6 days later in L than in S and a significant (P<0.05) reduction (21% to 36%) of ETa was observed in L vs S around this stage. Lower root abundance (reduction of 60%) and canopy size (reduction of 6% to 13%) in L have probably contributed to less ETa. In addition, the ontogenic delay exposed crops grown in L to more stressful meteorological conditions during the period around silking. Kernel number (KN), closely related to grain yield (r2>0.65), was significantly associated with daily ETa around silking. The modern hybrid, which had the highest production stability coefficient, established a greater KN mm-1 d of ETa (853 kernels m-2 mm-1 d) compared with the older ones (386 kernels m-2 mm-1 d). This characteristic may mask the deleterious effects of long-term cropping on maize grain yield.