Nitrogen accumulation in plant tissues and roots and N mineralization under oilseeds, pulses, and spring wheat

Abstract

To understand how pulse and oilseed crops might use nitrogen (N) more efficiently under varying levels of water and N availability in soil, we conducted a 2-year field study to monitor N accumulation in aboveground (AG-N) and root material at five growth stages, for canola (Brassica napus L.), mustard (Brassica juncea L.), chickpea (Cicer arietinum L.), dry pea (Pisum sativum L.) and lentil (Lens culinaris Medicum) alongside spring wheat (Triticum aestivum L.). Crops were grown in lysimeters (15 cm diameter × 100 cm deep) installed in the field in southern Saskatchewan, Canada. AG-N in all crops was greater under high-water than under low-water conditions. In oilseeds and wheat, AG-N increased until flowering then tended to level off, while in pulses it increased gradually to maturity. At maturity, dry pea and wheat had the greatest AG-N and mustard the least. Enhanced water availability increased seed N but did not affect straw N; consequently, N harvest index was greater under high-water than under lowwater conditions. Root N increased until late-flowering or late-pod (dough stage in wheat) then decreased to maturity. Mustard had the lowest root N, chickpea the second lowest, and canola, wheat, dry pea, and lentil the highest. Improved water availability increased root N for oilseeds and wheat but did not affect root N in pulses. At maturity, average root N of oilseeds, pulses, and wheat was 14, 17, and 20 kg ha -1 , respectively. At the seedling stage pulse crops had about 27% of total plant N in their roots, a much greater proportion than for the non-legumes. However, by maturity all crops had about 14% of plant N in their roots. Soil NO 3 -N increased gradually between seedling and maturity in non-legumes but in pulses there was a sharp spike at early flowering. Estimated apparent net N mineralized was similar for wheat and pulse crops which were greater than for canola and mustard. Soil N amounts and temporal change patterns varied substantially among crops evaluated, and these differences need to be considered in the development of diverse cropping Plant Soil (2010) 332:451-461 systems where cereals, legumes, and oilseeds are included in rotation systems.

Gross nitrogen mineralization in pulse-crop rotations on the Northern Great Plains

“…In a comparison of wheat, oilseeds and pulses at the Swift Current site, Gan et al (2010) observed maximum accumulation of NO 3 --N under wheat, but similar accumulations between oilseeds and pulses (including field pea and lentil). Canola and wheat were also found to have comparable root N (kg N ha -1 ) compared to pulse crops (Gan et al 2010) indicating that despite the ability of pulse crops to fix their own N, the below-ground residues may not have a greater contribution to the net N benefit compared to fertilized wheat or oilseeds. Interestingly, they also observed similar apparent net N mineralization under W-CNL wheat-canola; W_0N continuous wheat, no N fertilizer; W_WN continuous wheat with N fertilizer; W-FP wheat-field pea; W-L wheat-lentil wheat and pulses, but rates under oilseeds were about 50 % lower (Gan et al 2010).…”

“…Canola and wheat were also found to have comparable root N (kg N ha -1 ) compared to pulse crops (Gan et al 2010) indicating that despite the ability of pulse crops to fix their own N, the below-ground residues may not have a greater contribution to the net N benefit compared to fertilized wheat or oilseeds. Interestingly, they also observed similar apparent net N mineralization under W-CNL wheat-canola; W_0N continuous wheat, no N fertilizer; W_WN continuous wheat with N fertilizer; W-FP wheat-field pea; W-L wheat-lentil wheat and pulses, but rates under oilseeds were about 50 % lower (Gan et al 2010). This last finding may be supported by Sangster et al (2010), who found significantly higher total root biomass in canola compared to field pea (including both living biomass and root exudates, quantified using 13 C labeling), but also noted that based on its biochemical composition, canola root biomass was likely more recalcitrant than field pea root biomass.…”

“…Most studies of N benefits from legumes have been conducted based on a comparison of cereal versus pulse crops (Lemke et al 2007;Lupwayi and Soon 2009); however, accumulation of mineral N has been associated with both pulse and canola (oilseed) crops (Kirkegaard et al 1999;Ryan et al 2006). In a comparison of wheat, oilseeds and pulses at the Swift Current site, Gan et al (2010) observed maximum accumulation of NO 3 --N under wheat, but similar accumulations between oilseeds and pulses (including field pea and lentil). Canola and wheat were also found to have comparable root N (kg N ha -1 ) compared to pulse crops (Gan et al 2010) indicating that despite the ability of pulse crops to fix their own N, the below-ground residues may not have a greater contribution to the net N benefit compared to fertilized wheat or oilseeds.…”

“…This study took advantage of established research plots in the Northern Great Plains that included cropping rotations both with and without pulse crops. This should allow a broader perspective on the longer-term effect of pulse crops in the rotation (Gan et al 2010). The primary objective of this paper was to evaluate the effect of pulse crops in the rotation on gross mineralization rates, including the variability of these rates across the growing season.…”

Sulanan ve sulanmayan koşullarda yetiştirilen nohut (Cicer arietinum L.)’un gelişme seyrinin belirlenmesi

“…Tanede azot içeriği sulanan koşullarda (% 3.409) sulanmayan koşullara (% 3.272) oranla daha yüksek belirlenmiştir. Bunun nedeni generatif devrede yüksek olan azot içeriğinin ve kuru madde miktarının sulanan koşullarda taneye daha fazla taşınmasıdır (Gan et al 2010;Yağmur & Kaydan 2011).…”