Available at: https://digitalcommons.calpoly.edu/theses/170
Date of Award
MS in Agriculture - Soil Science
Earth and Soil Sciences
Dr. Terry Smith
Rice (Oryza sativa L.) is an important crop in many countries. According to the IRRI, more than 2 billion people globally depend on rice as a staple food (Dawe, et al. 2003). Studies on micronutrient content in rice and the effect of water in availability of the nutrients may aid in decreasing global nutrient deficiencies. Rice is grown under different water regimes such as AWD and intermittent flooding, sprinkler and furrow irrigation. A greenhouse pot experiment of rice utilizing a split plot design under different water regimes was conducted to assess the affect of water on (1) DTPA extractable soil micronutrients Fe, Mn Cu and Zn; (2) stem micronutrient concentration and uptake of rice (Oryza sativa L.) alone and with ground legume incorporated; and (3) yield of rice. The water regimes included: (1) rice pots watered to field capacity, or well-drained (drain); (2) pots submerged for 3 weeks, dried down for 1 week, then re-submerged for three weeks, or alternate wet and dry (AWD); and (3) continuous flooded (flood) conditions. A preliminary study which examined vegetative yield and micronutrient uptake of rice, faba beans, and sesbania using two different soils (Zaca clay and a loam) under flooded and drained conditions was conducted. Ground sesbania from the exploratory experiment was used for the study to explore the effects of organic matter (OM) on yield and micronutrient content. All DTPA extractable soil micronutrients except Zn were highest in the flood and AWD water treatments and in the lowest pH value. The DTPA extractable Zn values in the drain water treatment were twice as high as the AWD and flood water treatments. Stem Zn concentration was highest in drained, whereas Fe, Mn and Cu stem concentration were highest in AWD and flood treatments. Addition of sesbania incorporated into the soil only affected Mn soil micronutrient concentration, where Mn soil content was observed to be higher in the flood treatment with sesbania incorporated into the soil. Grain weight and grain to stem ratio were significantly increased by AWD and flood water treatments (p<0.05). Organic matter (sesbania) incorporated into the soil did not affect Fe, Mn, Cu or Zn stem to grain ratio. A comparison of stem concentration to grain yield highlighted the effects of Mn and Zn content on yield. Manganese stem content was highest in AWD and flood treatments where grain yield and grain to stem ratio were highest, while Zn content was lowest in AWD and flood treatments. Zinc stem content was highest in the drain treatment.