The leaf area index increased linearly as the plant population of corn (Zea mays L.) was increased from 34,500 to 69,000 plants per hectare. The leaf area per plant, however, decreased as the plant population increased. Nitrogen rates of 112 to 280 kg per hectare and row width had no effect on leaf area per plant nor the leaf area index. The yield of grain per plant was dependent upon the leaf area per plant. The efficiency of a given leaf area to produce grain was higher as nitrogen rates increased. The yield of grain per hectare of the long season hybrid was not influenced by row width except under drought conditions where 53‐cm wide rows gave higher yields than 106‐cm wide rows. Highest grain yields were obtained at 280 kg of N per hectare and 51,750 plants per hectare. Maximum yields were obtained with a leaf area index of 3.5 and remained constant up to an index of 4.5 with adequate nitrogen.

In recent years, the intensification of livestock production in Southern Chile has resulted in a high potential for environmental damage through nitrogen (N) losses, creating the need for the evaluation of N flows from these systems. The aim of the research was to determine N budgets and N use efficiency in two grazing systems in Southern Chile. For this, inputs and outputs were measured during one year on two grazing systems (heavy grazing, HG; and light grazing, LG). Also, a control treatment with no grazing (C) was considered. The annual N soil budget was determined by the difference between all N inputs (Σ inputs) and all N outputs (Σ outputs). The results of the experiment indicate that HG treatments received the biggest N input (427, 359 and 288 kg N ha -1 yr -1 for HG, LG and C treatment, respectively), however this treatment also had the biggest N losses (406 kg N ha -1 yr -1 ), with a nitrogen recovery efficiency from fertilizer of 71%. In addition, herbage dry matter yield (DM) was greater in the HG than in the LG and C treatments (10.4; 8.1 and 7.1 t N ha -1 yr -1 , respectively). Also, N concentration in the forage was higher in this treatment (2.9%) than in the LG (2.7%) and C (2.5%) treatments. The results indicate that HG increases N use efficiency in pastures in Southern Chile, increasing the herbage production and quality, but also increasing the potential for N losses to the wider environment. Farmers should consider this when choosing the appropriate grazing system.