And if it turns out the cheapest and best "tech" is soil conservation, what then?
"Tech" tends to mean high-tech, but high-tech is also high cost (see vertical farming). It's quite possible that low tech / appropriate tech solutions will win in the end.
Also, how many decades of R&D delay for this (rather... ambitious) Replace All The Plants Project are you asking for? The whole 60 years? Or should we tap the brakes (ie implement known soil conservation techniques) before going off the cliff?
Playing devil's advocate, there's no guarantee that these trends will continue. For a related example of this go and look up the Malthusian catastrophe
Several of the farms around where I live still use 40+ year-old farming equipment. Most likely, any new tech won't be deployed fast enough to make a difference, at least not on a global scale.
> A major environmental concern known as topsoil erosion occurs when the topsoil layer is blown or washed away. Without topsoil, little plant life is possible. The estimated annual costs of public and environmental health losses related to soil erosion exceed $45 billion. Conventional agriculture encourages the depletion of topsoil because the soil must be plowed and replanted each year. Sustainable techniques attempt to slow erosion through the use of cover crops in order to build organic matter in the soil. The United States alone loses almost 3 tons of topsoil per acre per year.[10] This is of great ecological concern as one inch of topsoil can take between 500 and 1,000 years to form naturally.
> Based on 2014 trends, the world has about 60 years of topsoil left.
So yeah go ahead feed the overpopulation of the hungry, hopefully in 60 years there is tech to replace all the plants that can no longer be grown. In 60 years this is going to be another global warming situation that we have known about but yet let continue until we could no longer do so.