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Pak. J. Bot., 45(S1): 83-90, 2013.

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SHOOT: ROOT DIFFERS IN WARM SEASON C₄-CEREALS WHEN GROWN ALONE IN PURE AND MIXED STANDS UNDER LOW AND HIGH WATER LEVELS

AMANULLAH¹ AND B.A. STEWART²

Abstract: Shoot: root (S:R) response of three warm season C₄-cereals (grasses) viz., corn (Zea mays L., cv. Hybrid-5393 VT3), grain sorghum (Sorghum bicolor L. Moench, cv. Hybrid-84G62 PAT), and foxtail millets (Setaria italica, cv. German Strain R) grown in pure and mixed stands was investigated at one month interval in pot experiment at West Texas A&M University, Texas, USA during spring 2010. The results indicated that the three warm season grasses responded differently in terms of S:R when grown in pure and mixed stands under low and high water levels at different growth stages. In the mixed stands, the roots and shoot biomass accumulation in millets decreased while its S:R increased and was considered the least competitor in the mixed stands than sorghum and corn. Corn plants on the other hand with higher root and shoot biomass accumulation but lower S:R was ranked first (strong) in terms of competitiveness in the mixed stands. In contrast, grain sorghum in the mixed stands produced more root and shoot biomass while grown mixed with millets, but produced less root and shoot biomass in the corn mixed stands  was therefore ranked second  in terms of competitiveness (corn > grain sorghum > millets). Better understanding of root architecture of different crop species in pure and mixed stands could maximize water and nutrients uptake. Early emergence of the three crop plants had positive effects on shoot and root biomass accumulation and was considered the best criteria in crops competitiveness. We also found that decreasing water level increased root biomass which declined the S:R in all three crop plants. With advancement in crop age, increase in shoot biomass was more than root biomass, and therefore, reduction in S:R was observed. We suggests that more studies are required to assess more accurately the root biomass contribution of different crops species in pure and mixed stands to improve carbon sequestration into the soils under different environmental conditions.

¹Department of Agronomy, Faculty of Crop Production Sciences, Khyber Pakhtunkhwa Agricultural University, Peshawar, Pakistan;

²West Texas A&M University, Canyon Texas-USA

^*Corresponding author’s e-mail: amanullah@aup.edu.pk & amanullah.aup@gmail.com