Comparative study for the estimation of single leaf area in maize and for the verification of two different leaf area meters

Investigations on methods of estimating single leaf area in maize were carried out at Keszthely Agrometeorological Station during the 1996 and 1997 growing seasons. At the same time, two portable automatic planimeters of different construction were studied. Two maize hybrids with short growing seasons were grown in the field. The area of the investigated plot was 0.5 ha, with a plant density of 7.2 m(-2). The difference in the leaf areas calculated with the classic Montgomery equation and with a standard was about 8% in both hybrids. To improve the results, the constant in the equation was reduced by 0.05 for the top leaves of the plant, close to the tassel. The leaves were grouped into three categories depending on their shape, which is a function of where the leaf is located within the plant canopy. Changes in leaf shape were determined by using leaf cross sections every 5 cm. This modification of the constant in the Montgomery equation for the top leaves improved the leaf area estimation of the whole plant by 3%. A portable leaf area meter of the LI-COR 3000 type was tested both in the laboratory and in the field. The instrument gave excellent results in both situations. When the instrument is used under field conditions, attention should be paid to the frequent cleansing of the sensor head, especially during the flowering of maize. The other instrument studied was a laser leaf area meter of the CI-203 type. In the case of field application, the error of estimation was very high (25.47%). The instrument was sensitive to open-air field conditions. There is a cylinder within the sensor head, that measures the lenght of the leaves. The movement of this cylinder is often hindered by various particles (dust, pollen etc.). Continous cleansing and checking even during application was needed to get correct area results. The laser area meter can be recommended mainly for laboratory investigations, because its memory capacity is not large enough for series of measurements in the field. Its total capacity was only the area data of 20-25 whole plants. A larger quantity of data disturbed the transfer to the computer and sometimes caused loss of samples.