Inga alley cropping experiment update

I have been following the development of Inga alley cropping in south america for quite a while and I am very excited by the results to date.

https://www.ingafoundation.org/alley-cropping/

The idea is to use rows of densely planted ice-cream bean (inga) allowed to grow to 2-3 m to form a weed suppressing canopy and dense mulch to create a weed free space. You then chop back the trees, chop and drop the resulting green mulch, and sow an annual crop like maize through the mulch. This is easier than clearing grass to sow, protects the soil from disturbance and erosion, enriches the soil with nitrogen and deep soil minerals, and also provides firewood and fodder for animals if wanted (goats adore inga leaves and pigs love the pods). By the time the inga canopy closes over the crop is finished, then you rest the land until ready again.

I have started my own trials now I have farming land to work on. I have started on a section of creek flats that occasionally gets inundated by slow moving water for about half a day each year. The soil here is deep and silty. The area was originally kikuyu pasture. I cleared it back with glyphosate last winter in 2014 over a patch of about 40 x 10 m making three long cropping rows between four rows of alley trees. (say what you will about the choice, but I am content to use it for landscape transformation as long as I don't get in the habit of using it for repeated maintenance). I sowed the main alley rows with pigeon pea as a pioneer last spring in 2014 and now they are all about 3 m tall and nicely shading the tree rows. I also planted bare root seedling Inga seedlings about 5 cm high in the spring from a mass planting pot, but about 90% of them didn't take due to the very dry spring. I suspect the direct sunlight finished them off as well- dry shade might be tolerated better. This autumn after the summer rains I planted out 10-15 cm tall Inga seedlings grown on over summer in 4cm tubes, about every 50cm within the rows. The shade from the pigeon pea made establishing them much easier. I also tried sowing excess Inga seed directly into the positions, but I was worried about rats taking them so sowed them about 2.5 cm deep, too deep it appears so only about 10% germinated successfully (lots of others found germinated but still buried a month later). The area also grew a magnificent crop of about 10 feedbags full of open pollinated white maize over summer, and I could have sowed twice as much again in the space. The ground is gradually covering up with Vigna parkeri and other soft weeds, and I spot spray/hand weed/ hoe any reestablishing grasses.

I think next patch of pasture I will clear this winter, spring sow pigeon pea and other crops and then surface sow the Inga seed in the early autumn and just cover with a handful of hardwood mulch. This will save on potting and maintaining the Inga seedlings all summer, and making planting them out a lot faster (I can sow 40 seed positions in about 20 minutes, versus an hour for seedlings that need a deeper hole and greater care). Some of the few Ingas that did establish in the spring are now over a foot high, so they can grow quickly once established. I figure by the time the pigeon pea are running out of steam (2-3 years) the inga will be big enough to take over their role.

I also think the system will work very well with arrowroot as the crop between the inga rows. This crop is ideal because it is tolerant of being harvested at unpredictable times, and also relatively shade tolerant, making the timing of pruning the inga easier. It also grows it tubers above ground so soil disturbance will be minimal (unlike cassava) and its aerial parts also make good animal fodder. I will be planting the first section rows to arrowroot tubers over the winter so they can take off in spring.

Interested to hear if anyone has some feedback on my approach or suggestions. I'm in subtropical Australia, mild frosts every few years, hot humid summers, unpredictable rains at times, reasonably good old volcanic soil.

 

The Pigeon Pea will self-sow in the rows easily but I suppose the Inga, with some care, will crush those seedlings when they can.

I had better results with 150mm Inga as opposed to 100mm pots, the 150 did get a good jump on them. I'd assume your autumn seeded germinations will appreciate having a dense frost protecting from the Cajanus.

Are you chop-dropping the Cajanus on any timed system during? You could collect the seed after Winter, then chopdrop around the Inga. Speaking of which, can you maintain some seed collection of the better stock, I've run through all of mine. I hand sowed my collection and wished for a tool such as yours, I ended up putting 5 seeds a hole as it was getting painful.

I can see your theory behind the Cassava but you could move that mass bulk (and great mulch/fodder) to the rows after a growing season and then use that disturbance to run an annual green manure crop or other annual food. You could broadcast sow the seed and then harvest the cassava, all your walking on the rows, ripping up tubers and dropping leaves would set many seeds up for germination. A nice sunflower would look fantastic on contour amongst the Cajanus and Inga? Those dense canopies should keep the grasses at bay. Edit: Temporarily while the rows get established, I mean.

and they are multi-stacking the rows for successional timed removals over the life of the row. Bit different for yours when the pioneer is the climax but it may give you an idea or too. Not sure if I already sent you this one: https://vimeo.com/119906026


Edit: Post that photo of the corn rows. Might get a comment or too.

 

I'd be more worried about the inga self sowing than the pigeon pea- after six months they are really hard to pull out. I figure every fruiting season will involve chopping the immature pods, hopefully mature pods one day to feed livestock. I can definitely see larger inga seedlings getting off to a quicker start, but after planting 200 of them out in that one small plot I am looking for any way to speed up the process, hence wanting to go the other way and plant seed. Having a smaller number of seedlings in tubes to fill in gaps seems to be the better approach to me. I agree the Cajanus canopy will help get the inga seedlings through their first critical winter, and was planning pruning the cajanus if necessary as the inga grow, but I suspect the morning and afternoon sun between the rows will be enough (the rows are oriented north/south).

I can see your point with using the cassava harvest disturbance to get the next seed crop growing, but can see a few problems. Cassava is pretty hungry so the soil might need a cycle of inga growth to recharge it. The place also floods occasionally, so I wouldn't want bare soil in case of water erosion. Im even considering east/west vetiver rows crossing the inga rows to slow flood water travelling north/south (might even help catch extra flood silt).

No luck uploading the pics.....doesnt seem to want to work.

 

Here is the photo bucket link to some images of the inga rows

 

In alleycropping the trees are generally cut back at least once a year so don't produce seed.