Sunday, 9 July 2006
2-9

Water Use and Plant Uptake of N and P in Relation to the Growth of Durum Wheat.

A. Fares Asfary1, A. Wahbi2, and M. Al. Oudat1. (1) Atomic Energy Commission of Syria, Dept of Agriculutre, Damascus, Syria, (2) International Centre for Agricultural Research in the Dry Areas (ICARDA), P O Box 5466, Aleppo, Syria

In a field experiment conducted in two successive seasons at Tel Hadya (Northern Syria) and in one season (2nd season) at Izraa (southern Syria). The seeds of local durum wheat (cv. Hourani) were irradiated with gamma irradiation doses 0, 5, and 10 Gy, and sown later in a randomized complete block design. At Tel Hadya, the fertilizer treatments included: two P rates (0 and 17.8 kg P ha1) and 50 kg N ha-1 in the first year and 0 and 50 kg N ha-1 in the second year. At Izraa; there were only two treatments: 0 and 40 kg N ha-1 t. Dry matter production, N and P uptake, and soil moisture contents at surface and deep soil layers using neutron probe were measured,, during the growing season in all experiments. Root samples were taken throughout the season at Tel Hadya only.

Phosphorus application significantly increased DM at tillering only. Nitrogen fertilizer increased significantly DM (13%) and grain (10%) at Tel Hadya whereas at Izraa the differences were insignificant. The highest growth rate was 174 kg ha-1 d-1 for 41 days between stem elongation and anthesis at Tel Hadya in the first reason.

Water use efficiency increased by seed irradiation with N fertilization at Tel Hadya by 20 and 18% for total DM and grain respectively but was reduced at Izraa, whilst no effect was observed with P. The contribution of soil moisture content at early growth (3-4 leaf stage) to total water use by crops were 78, 74 and 3% at Izraa and at Tel Hadya second and first season respectively. The major depletion of soil moisture occurred during tillering and anthesis (March- April). The contribution of soil moisture and depletion was dependent on total precipitation, rainfall distribution and crop development.

Phosphorus fertilizer also increased P & N uptake in the early stages of growth, whereas N application increased P uptake at Tel Hadya during early growth and significantly increased N uptake at Tel Hadya with insignificant increases at Izraa. The highest P uptake rate (0.016 g/m2/d) occurred between stem elongation and anthesis at Tel Hadya and for the highest N uptake (0.124 g/m2/d) between seedling and stem elongation at Izraa.

P fertilizer application significantly increased root length at stem elongation and harvest in the first season, whilst no response was observed in the second season. On the other hand N significantly increased root length for both seasons. The root length (km m-2) at anthesis, for all treatments, was in the range of 13.81- 13.85 in the wet season and 7.65 8.27 in the dry season. However 50% of root system was in the top 30 cm soil layer.

Keywords: Soil moisture, neutron probe, nutrient uptake, yield response, wheat, seed gamma radiation, root length, fertilization, nitrogen, phosphorus, Mediterranean, Syria.


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