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Variable rate irrigation (VRI) is a new irrigation method developed in precision agriculture. VRI technologies allow the producers to site-specifically apply irrigation water at variable rates within a field to adjust the temporal and spatial variability in soil and plant characteristics. Use of VRI in agricultural production has the potential to improve water use efficiency. Developing VRI practice and documenting the benefits of VRI to producers are critical to accelerate the adoption of VRI technologies. Comparison of VRI with uniform rate irrigation (URI) in soybean and corn crops was studied in Stoneville, Mississippi, USA. A center pivot VRI system was employed for delivering irrigation water. Soil apparent electrical conductivity (EC) of the fields was used to delineate VRI management zones and create VRI prescription. Irrigation was scheduled using soil moisture content measured by soil moisture sensors. Crop yield and irrigation water productivity in VRI treatment was compared to that in the URI treatment. There was no significant difference in yields of soybean and corn between VRI and URI treatments. Compared to URI, VRI treatment saved 25% irrigation water in soybean and 21% irrigation water in corn. Irrigation water productivity (WP) of VRI was 31.2% and 27.1% higher than the URI in soybean and corn, respectively. Results demonstrated that VRI management was superior to the URI in terms of water use efficiency. Soil EC coupled with soil physical properties could be used to establish VRI management zones. Development of novel algorithms with more inputs to site-specifically determine appropriate amount of water to apply is a major challenge facing VRI industry.

Purpose To describe the phenotype and genotype of three Mainland Chinese families affected by choroideremia (CHM). Methods Complete ophthalmic examinations were conducted in three unrelated Chinese families with CHM. Peripheral blood samples were collected from the families for genetic and immunoblot analysis. All exons and flanking intronic regions of the gene encoding Rab escort protein-1 (Rep-1) were amplified with PCR and screened for mutations with Sanger sequencing. The three-dimensional structure of mutated Rep-1 was modeled using sequence homology with rat proteins to analyze the effect of the mutation detected in one family. Results All affected males had characteristic signs and symptoms of CHM; however, central visual acuity impairment occurred earlier than expected. All female carriers older than 45 years had pigmentary changes, and one female carrier was symptomatic with vision loss. Three different mutations in Rep-1, c.1801–1G>A, c.1130 T>A, and c.612delAG, were detected in the three families. Conclusions In Mainland Chinese families, the central visual acuity of male patients with CHM can be affected at an early age (second decade), whereas female CHM carriers may manifest signs and symptoms at a later age (≥45 years). One previously reported and two novel Rep-1 mutations were detected in three Chinese patients with CHM.