Narrow rows and high maize plant population improve water use and grain yield under conservation agriculture

The relationship between maize (Zea mays L.) population density and grain yield is influenced by soil and crop management strategies, including Conservation Agriculture (CA). However, little is known about the response of maize grain yield to varying plant population and/or row spacing under CA. A 3-yr study was conducted under CA to evaluate the effects of plant population and row spacing on maize grain yield, plant available soil water, and soil temperature. Plant populations ranging from 40,000 to 80,000 plants ha(-1) were evaluated at three row spacings (0.5, 0.76, and 1.0 m). The response of maize grain yield to plant population was highly variable between seasons: it was not affected by plant population in the season with the highest early season rainfall but increased with increasing plant population in the driest season and in the season with well-distributed, near average rainfall. Higher plant populations resulted in lower soil water levels, presumably due to greater water extraction. Plant population affected soil water availability in the 20- to 80-cm soil layer in Season 2, while plant population affected soil water availability at all soil layers except the 10- to 20- and 60- to 80-cm soil layers in Season 3. Rapid maize leaf-canopy closure provided by increased plant population and narrower row spacing is critical to adequately utilize the benefits associated with CA.