The influence of the planting density and soil moisture on the foliar surface index and the net rate of assimilation

--Gavrilescu, L, Bonea, D, Dobre, M, Paraschivu, M

Former research carried out at the Research Station of Simnic have shown that planting density is the major factor that influences the physiological processes which, in turn, determine the level of the yields.

The present paper deals with four corn hybrids (F322, F376, Olt, Cocor) planted at different densities (40,000; 50,000; 60,000) and in two soil moisture conditions (irrigated and unirrigated) within the 1999-2001 period, on a luvic brown-reddish soil with a 5.8 pH. Climatically, 1999 was relatively favorable for the corn crop, and 2000 was extremely dry, with a large soil water deficit and high air temperatures. In 2001, a soil moisture deficit was recorded beginning with the end of July and August, as well as very high air temperatures.

The foliar surface of each plant (FSI) was calculated per square meter of soil and as average values over three years.

The study carried out with the irrigated crop (Fig. 1) emphasizes the role of water for optimal physiological processes. There was a 58% increase in the FSI with the F322 hybrid at a 50,000 plant density in comparison with a 40,000 plant density, followed by the Olt hybrid which, with the same plant density, had a 39% increase in comparison with the minimum density (40,000). The F376 and Cocor hybrids have a FSI of 25–26% with the maximum density in comparison with the minimum density.

Figure 1. The FSI in function of the plant density and corn hybrid with irrigated plot

With the unirrigated crop (Fig. 2) the FSI values range between 1.16-1.68 m²/m² with the F322 hybrid (49%); between 1.64–2.02 m²/m² with F376 (23%); between 1.25–1.72 m²/m² with Olt (37%) and between 1.46–1.89 m²/m² with the Cocor hybrid (29%).

Figure 2. The FSI in function of the plant density and corn hybrid with unirrigated plot

It can be noted that there is a difference between irrigated and unirrigated, as well as between densities, of approximately 14% with F322, 3% with F376 and 2% with Olt.

We conclude that (1) The FSI increases with the plant density, the maximum value being recorded with the maximum density (60,000), both with irrigated and unirrigated plants; (2) With regard to the ISF, the best results were given by F322 (irrigated) and F376 (urirrigated).