Physiological impacts of soil moisture stress and plant population on leaf gas exchange and radiation use of maize

Soil moisture stress is the major future threat for sustainable crop cultivation to the forthcoming generation. The soil moisture stress and plant population experiment conducted with maize (Zea mays L.) (COH(M)5) crop at Coimbatore, India during the year 2009. Treatments imposed are three soil moisture levels 100% irrigation water (0.8 IW/CPE ratio), 75% irrigation water (0.6 IW/CPE ratio) and 50% irrigation water (0.4 IW/CPE ratio), plant population treatments are Normal spacing (60x20 cm), Narrow spacing (45x20 cm) and Reduced narrow spacing (30x30 cm) levels. The increases in plant population, which will alter the radiation use efficiency, absorbed PAR, light extinction co efficient (‘k’). The reduction in yield of maize by the reducing soil moisture was compensated by increasing the plant population which leads to change in radiation use efficiency, absorbed PAR and light extinction co efficient (‘k’) that causes improvement in chlorophyll content, photosynthetic rate, dry matter accumulation and yield of maize. Yield increment of narrow planting by 5%, 6% and 13% over the normal spacing in 50%, 75% and normal water requirement respectively. The normal Irrigation (0.8 IW/CPE ratio) level with narrow spacing (45x20cm) observed as best with increase in yield of 800 kg ha⁻¹ over the control, which was supported by RUE, APAR, Pn, g_s, RWC and chlorophyll content.