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New maize hybrids has been intensively used as the first and second crop at the Cukurova region of Turkey in recent years. Therefore, nutritional problems of corn needs to be solved for the optimum yield, and protection from the potential insect and disease damages. Influence of nitrogen (N) and row spacing (RS) on corn yield, grain protein content, and selected plant parameters have been studied under field conditions in 1994 and 1995. Nitrogen was applied in the rates of 200, 250, 300, and 350 kg N ha-1 to main plots where row spacings were 10, 15, 20, and 25 cm in each subplots. Phosphorus (P) and potassium (K) were applied to each plot as basal rates. The experiment was arranged in a split-plot design in three replications. During course of the experiment and after harvest, selected plant parameters, leaf nutrient contents, root length, grain yield, and crude protein content were measured, and the data were statistically analyzed for determination of treatment effects. The selected plant parameters either influenced by N, RS, or both in 1994 and 1995. The leaf N content was affected by N and RS in 1995, and a RS effect was only observed in 1994. Grain yield was influenced by RS and N and RS in the first and second years, respectively. Grain yield ranged between 7.3 to 12.8 Mg ha"1 for both years. Treat ment effects on crude protein content was significant in 1994 but no response was obtained in 1995.

Although the plant root system is one of the most important plant parameters affecting nutrient uptake by plants, root studies in field experiments are rarely conducted in plant nutrition and fertility studies. Since collection of root samples and measurements are difficult and time consuming, they are not considered as a routine plant parameter. Therefore, the effect and importance of the corn root system on plant nitrogen (N) uptake and grain yield was studied under field conditions in Adana, Turkey. Nitrogen was applied at rates of 200, 250, 300, and 350 kg N ha-1 as urea in a randomized complete block design experiment with three replications. During course of the experiment, soil, plant, root, and grain samples were collected and prepared for chemical analysis. Nitrogen uptake by plants was predicted using a COMP8 mathematical computer model and compared to actual plant uptake. Grain yield and leaf N content increased with increasing N rates, but root length did not change statistically. Predicted N uptake increased with added N, but was much smaller than observed N uptake under field conditions. Consequently, additional soil and plant parameters should be considered in nutrient uptake models to make the prediction more sensitive.

Economically valuable pistachio nut trees are extensively grown in the Southeastern part of Turkey. A great percentage of the total annual pistachio nut yield in Turkey is obtained from this region. However, fertility aspects of these pistachio trees have not been studied in detail. Thus, there is a need to determine the optimum fertilizer rates to increase the yield and quality of pistachio nuts. Fertilizer trials were conducted on an established 37 year-old-pistachio orchard. Inorganic nitrogen (N) and phosphorus (P) fertilizers were applied in three and two rates, respectively. Potassium (K) was added to all trees as a basal rate. In addition, selected trees received air-dried sheep manure, and additional inorganic macro- and micro-nutrients as a foliar application at three different times during the course of experiment. Fertilizer treatments influenced the fruit yield, productivity, fruit size, percentages of dehisced fruit shell, and nutmeat. Positive effects of these treatments on leaf element content, N, P, and K, were also obtained. Fruit protein and oil contents were not influenced by addition of organic and inorganic fertilizers.