title: Influence of nitrogen nutrition management on biomass partitioning and nitrogen use efficiency indices in hydroponically grown potato.
abstract: The National Aeronautics and Space Administration (NASA) has been conducting controlled environment research with potatoes (Solanum tuberosum L.) in recirculating nutrient film technique (NFT)-hydroponic systems as a human life support component during long-duration spaceflight. Standard nutrient solution management approaches include constant pH regulation with nitric acid (HNO3) and daily adjustment of electrical conductivity (EC) equivalent to half-strength modified Hoagland's solution, where nitrate (NO3-) is the sole nitrogen (N) source. Although tuber yields have been excellent with such an approach, N use efficiency indices are expected to be low relative to tuber biomass production. Furthermore, the high amount of N used in NFT-hydroponics, typically results in high inedible biomass, which conflicts with the need to minimize system mass, volume, and expenditure of resources for long-duration missions. More effective strategies of N fertilization need to be developed to more closely match N supply with demand of the crop. Hence, the primary objective of this study was to identify the optimal N management regime and plant N requirement to achieve high yields and to avoid inefficient use of N and excess inedible biomass production. In separate 84-day cropping experiments, three N management protocols were tested. Treatments which decreased NO3(-)-N supply indirectly through lowering nutrient solution EC (Expt. I), or disabling pH control, and/or supplying NH4(+)-N (Expt. III) did not significantly benefit tuber yield, but did influence N use efficiency indices. When supplied with an external 7.5 mM NO3(-)-N for the first 42 days after planting (DAP), lowered to 1.0 mM NO3(-)-N during the final 42 days (Expt. II), plants were able to achieve yields on par with plants which received constant 7.5 mM NO3(-)-N (control). By abruptly decreasing N supply at tuber initiation in Expt. II, less N was taken up and accumulated by plants compared to those which received high constant N (control). However, proportionately more plant accumulated N was used (N use efficiency) to produce tuber biomass when N supply was abruptly lowered at tuber initiation in Expt. II. Hence, a hydroponic nutrient solution N management system may be modified to elicit greater plant N-use while maintaining overall high tuber yield as opposed to achieving high tuber yields through excess N supply and shoot growth.
authors.affiliation: Dynamac Corporation, Kennedy Space Center, FL 32899, USA. gregory.goins-1@ksc.nasa.gov
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Goins
authors.forename: Neil C
authors.initials: NC
authors.lastname: Yorio
authors.forename: Raymond M
authors.initials: RM
authors.lastname: Wheeler
mesh_terms: D018533:Biomass; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D018504:Ecological Systems, Closed; D005308:Fertilizers; D006863:Hydrogen-Ion Concentration; D018527:Hydroponics; D008021:Life Support Systems; D009566:Nitrates; D009584:Nitrogen / Q000172:deficiency / Q000378:metabolism* / Q000493:pharmacokinetics; D018517:Plant Roots / Q000254:growth & development; D018547:Plant Stems / Q000254:growth & development; D011198:Solanum tuberosum / Q000254:growth & development* / Q000378:metabolism*; D013026:Space Flight
chemical_list: D003470:Culture Media; D005308:Fertilizers; D009566:Nitrates; D009584:Nitrogen