Onion response to nitrogen doses and planting density

الملخص EN

Field experiments were conducted during the 1999/2000 and 2000/2001 growing seasons in the Agricultural Research Station - University of Jordan in the Jordan Valley, in order to evaluate onion (Allium cepa L.) response in terms of dry yield and nitrogen absorption (kg/ha) to planting densities and nitrogen doses.

The impact of wasted nitrogen portion (added N – removed N in kg/ha) in relation to each dose on the environment was also studied.

The following factors: Two planting densities (i.e., 67 and 83 plants/m2) and six nitrogen doses (i.e., 100, 120, 140, 160, 180 and 200 kg/ha) were tested on the short day cultivar “Texas Early Grano 502”.

Numerically, nitrogen application at rates between 120 and 200 kg N/ha gave higher yields than 100 kg N/ha at both planting densities during both growing seasons.

Nitrogen uptake by onion plants was the lowest with 100 kg N/ha at both planting densities during both growing seasons.

Nitrogen content in onion bulbs with 160 kg N/ha was significantly higher than lower rates at the lower planting density and with 140 kg N/ha at the higher planting density in the first growing season, while it was numerically higher with 180 and 200 kg N/ha during the second growing season at both planting densities.

Consequently, nitrogen loss was the lowest at the lowest rate of nitrogen application.

The loss was increased with higher rates of application.

As there were no significant yield differences among rates of nitrogen application beyond the 120 kg N/ha, it is concluded that additional nitrogen amounts are not necessary for boosting yield.

Instead, unutilized nitrogen will eventually volatilize or leach down in the soil, thus contaminating the environment.