Make your own compost the easy way, grow it and cut it! A green manure crop is grown to replenish and feed the soil. Instead of leaving vegetable garden space fallow over winter, sow these crops instead. Come spring time these crops can be turned back into the soil ready for the summer growing season. A winter green manure crop also acts as a living mulch and reduces loss of soil when it is windy. It is an easy way to provide organic matter to your garden as it is grown in situ – no wheel barrowing heavy loads across the garden!
Planting, growing and harvesting green manures.
Plant these crops in late summer and allow them to grow over winter. Cut down in early spring and let them breakdown for 3-4 weeks before sowing your spring crops.
The easiest and most cost effective way of growing these crops is by seeds. After you have harvested your crops, smooth over the soil with a rake and sow seeds according to the instructions on the packet. Then rake again lightly to cover seeds. Each crop will have different growing rates and harvesting times. When the plants start to develop flowers, it is time to cut down and plough back into the soil. It is as simple as that. If you let them set seed you may get a ‘weed’ problem.
These are the crops which I use as Green Manures
Phacelia-this is probably my pick as it has so many other benefits. The flowers are like ice cream for beneficial insects such as hover flies and lacewings. It does self seed but is not invasive so I let it come up where ever and just pull it out and use it as a mulch around vegetable plants if I want to use that growing space for plants. The attractive purple flowers look nice in the garden. Buy seeds through www.kingsseeds.co.nz or Yates.
Mustard seed-Sow this thickly. You can use the small seedlings in your salad or sandwiches. Plough it in when it is about 20cm high. Buy the seeds in bulk at most garden centres.
Lupins- These are great nitrogen fixers and release nitrogen back to the soil when cut down.
Broad beans and peas- I use these as an edible crop and then once the harvest is over I chop down the stalks into 10-20cm long pieces with a sharp hand saw or knife and then let it rot where it was grown. This will replace all the nitrogen back into the soil. I grow a ‘hungry” crop such as brassicas after this.
Oats-These provide quick cover and breakdown quickly when ploughed back into the soil. I often give the chickens a treat by feeding them a handful when sowing.
Corn, pop corn or maize and sunflowers- these are not strictly cover crops but what they do is replace carbon back into the soil. Plants cannot grow without carbon and eventually the soil structure collapses. This is what happened in the Dust bowl in USA in the 1930′s. Carbon holds the structure and nutrients of the soil together. After growing these crops cut the fibrous stalks into 20cm or smaller pieces and plough back into the soil.
Vetch-This is a good annual to sow for winter growth. It is a nitrogen fixer. It makes a great weed suppressant but don’t let it go to seed as it can become invasive. Buy in bulk from www.kingsseeds.co.nz.