Great question.

It is strange indeed: it seems a sort of 'rural' and/or technocratic point in a list of demands that is otherwise directed solely at cosmopolitan intellectuals and urban workers.

I've always struggled to explain it to my students when we tackle the Manifesto. So, I'll be excited to see a specialist on Marx or Socialism chip in her/his 2 farthings!

In the meantime, here's my own answer, which is a more generalized context:

Up through the 1840s (Marx & Engels wrote the Manifesto in 1847-1848), there was a great deal of interest in and talk about making lands "productive". And a lot of ink spilled by various reformers, by commercial- and scientific Societies, and (occasionally) by the odd forward-thinking political figure, on the need to increase the cultivation of "waste lands".

This notions (and/or rhetoric) in circulation about cultivating waste-lands tapped into three very different processes, though.

First:

• the draining of swamplands (with various engineering projects, such as canal and dam-building)

The late 18th and early 19th century was the golden age of European hydrology, with canal-building all over England, the straightening of the Rhine (see especially Blackbourn's outstanding book The Conquest of Nature), and so on. Indeed, in the French film Ridicule, the rational, enterprising young noble originally goes to Paris (on the eve of the Revolution) to secure funding for swamp-draining in his lands, in order to make them more productive. So, in this sense, "bringing waste lands under cultivation" tapped into this scientific, progressive discourse of swamp-draining. And it was not just about people actually draining swamps: as an anachronistic comparison, the rhetoric of swamp-draining might have corresponded in the 1790s to the rhetoric about high-speed rail today... namely, a sort of generalized invocation of rationality and/or applied technology, a shorthand for thinkers and politicians alike. (and it has persisted in politics as a metaphor, but we of course won't go into that...)

Marx certainly would certainly have encountered this rhetoric. Indeed, many of the French Revolutionaries of the early 1790s gave endless speeches about it in the National Assembly, and, as Marx was keenly attuned to the politics of the French Revolution (five decades earlier), he would certainly have read about it there, even if he hadn't been so interested in (what we today call) economics...which he in fact was.

Nonetheless: for this first meaning, drawing from hydrological projects, I get the sense that this is more Engel's idea (and voice). It's just so gosh-darn bourgeois in its rational reformism... and remember that Engels started out as a rational, reformer industrialist.

Second is:

• The (re-) allocation of former aristocratic-owned land to a local municipality (or more rarely, perhaps even subdivision to farmers)

Huge swaths of forest and other uncultivated areas had, by the 18th century had become "hunting" reservations for nobles, aristocrats, and great land magnates. In the 18th and early 19th century, there was a lot of pressure by local municipalities and governments to take it over, and make it 'productive.' The Grunewald Forest outside of Berlin was, in the 16th c., a hunting-territory for the Kurfürst Joachim II. Over the 18th century, though, it came more and more to be used to supply lumber and charcoal to the growing city of Berlin. In short, over a century, this "uncultivated" aristocratic land was made "useful" for "the (towns)people". The evolution of the actual legal ownership of the forest is more complex--but also a bit beside the point, as it was certainly fully under the control of municipal authorities by the 1870s, when--with new rail access from Berlin--it became sort of nature spot for (well-off) Berliners. (its second life of "usefulness.")

In the big picture, then, this "making land productive" was the long-term process of the bourgeoisie wresting land away from an aristocracy that was "wasting" it (by reserving it for fox hunting and the like).

And Marx was all about this larger process of the efficiency-driven bourgeoisie wresting ownership of resources such as land away from a (less efficient) aristocracy of privilege: Marx literally wrote the book on it. (Das Kapital) So, making "waste" land productive--indeed, making it maximally productive-was a core part of Marx's theory of the bourgeoisie's raison d'être.

Related to this, of course, is the flip side... the third backdrop to cultivating waste-land:

• some of this rhetoric also taps into the much longer and older (17th century, primarily) process of "enclosure" (as it's known in English history).

Enclosure is where lands formerly held in common were deemed "little-used" or even "waste" lands... because the use of such lands by foragers, local herders, and tiny-scale peasant farmers was either not evident or deliberately disregarded. Declared 'waste-land', the land was then appropriated by 'gentlemanly' patrician (semi- or proto-capitalist) landowners through various legal shenanigans and other devious means, enclosed (usually more in the legal sense than with an actual fence), and put into crop-rotation worked with peasant-laborers. This hurt those on the margins of society quite a bit... and benefitted the large landowners quite a bit more. It's part of the long process that used to be called the Agricultural Revolution--Mark Overton's The Agricultural Revolution is key here-- but today we don't call it that anymore, because it's no longer cool to overuse the word revolution. But whatever it is called, the process certainly fed into industrialization (aka the process formerly known as the Industrial Revolution), in that dispossessing the rural poor of once-upon-a-time common land had the "benefit" (to the factory owner) of driving these poor sods into towns and eventually into factories to find work... at subsistence wages (i.e. dirt cheap). So, enclosure "freed up" labor (in the words of an economist)...

.... or in the words of Marx, enclosure turned a portion of the rural peasantry into the urban proletariat. Again, Marx would write the book on proletarianization, and the preceding enclosure movement in England loomed large as a precursor.

So, that's where we are, in terms of what Marx & Engels were drawing on.

But now, here's the problem with all three of these aforementioned contexts of waste-land cultivation (draining swamps; making aristocratic hunting lands productive; "privatizing' the commons):

all of these are indelibly associated with the bourgeoisie. Indeed, it was Marx himself (in the Manifesto itself and other writings) who so indelibly associated them with "the Bourgeoisie" in the first place.

So what in the heck is a BOURGEOIS process doing in a list of COMMUNIST demands??!

Here's where I speculate a bit.

My theory is this: that it is a triple-aimed gesture...

1. by Engels, aimed at middle-class readers and intellectuals to buttress the 'rational' and 'productivist' credentials of his and Marx's ideas to progressive intellectuals and middle-class elements

2. by Marx, as a way to differentiate his socialism from utopian, reformist, and other socialisms, by underscoring Communism's "scientific" nature using well-established rhetoric of rationalism ... i.e. "we're more scientific than the Owenites, because we're thinking about how to cultivate waste-land while they're back home swapping wives."

and

3. by Marx and Engels, as a shameless political crumb to throw at poor peasants. The land shortage, especially in German lands, was acute--it's why so many poor Germans were heading to America... to get land. But the same is true all over Europe. So, Marx is basically promising, "follow us: we'll get you the farmland you so desperately need."

But, these last three arguments, I don't know for sure. (please note the lack of cited sources) More pointedly, I don't know enough about the various programs of the Proudhonists, the Saint-Simonians, the Owenites, the Blanquists, etc., to know to what degree Marx was cribbing from their manifestos, or instead throwing in something to make "scientific" Communism seem different. Was there a narrower context in 1847-early 1848, that this demand spoke to? I'm not sure.

So, I am eagerly (eagerly) awaiting a Marxist/History of Socialism specialist to weigh in!!

--> But, regardless of the reason, the demand would prove very, very useful in the long run.

Though the Manifesto was largely ignored for a few decades, it gained new life after the 1870s, and in particular, after 1900... and in places that Marx never dreamed it would be relevant, such as imperial Russia or even (gasp) China.

And the note about cultivating lands proved to be a VERY useful lever with which to pry Communist ideas into the landscape of the Russian (and later, Chinese) peasantry:

"See, Marxism is not only about the industrial proletariat, we are also going to get each and every one of you peasants your own parcel of land! Free land for all peasants--it's all right here, in this classic treatise!"

Lenin and Mao both built a huge part of their following out of the dispossessed peasantry, so this little odd duckling about land reform in the long-obsolete Manifesto certainly helped to build modern Communist movements.

EDIT: on Owenite wife-swapping see Taylor's classic book Eve and the New Jerusalem... a great read.

can you give a bit more of info about what you're talking about? Which chapter, page etc?

Thanks in advance