Green Manure- Feeding The Soil

Friday, September 25, 2009
I've alluded to our use of green manure crops in a previous post. Basically, green manure or cover crops are the indispensable foundation of organic farming and sustainable land management. They are grown, not to be harvested, but rather as a fast growing crop to be incorporated into the soil before they reach maturity to contribute to the care and feeding of the soil.

We use green manures primarily to increase organic matter in the soil. The living and/or decaying plant material feeds and increases earthworms and beneficial micro organisms which alternately feed and create new, healthy soil and therefore plants (+ animals and people).  In the process, carbon and nitrogen is increased and as the soil structure is improved and can act like a sponge, improved moisture retention and air penetration is achieved along with better root penetration for the vegetables we grow. 

Oats, then garlic then neighbour's paddock of cow pasture.

Our paddock above in the foreground was virtually bare excluding patches of weeds when we first moved onto this land a couple of winters ago, having been mainly grazed and compacted by cows with the odd hay crop grown on it for many years. Improved soil structure, including the increased and deeper plant roots, also stabilises the soil to prevent erosion. Erosion has become a major factor in the degradation of Australia's agricultural lands. 

Currently we are working with our winter green manure crop of oats. Oats are great because they are very leafy and so produce lots of organic matter/bulk and carbon sequestration. This is particularly important for us with our red volcanic soil which is very fertile by nature but also lacks organic matter and so tends to dry out easily during summer. They grow well in the cold and wet. Our oats have gone wild this winter with all the rain we've been getting. 

Our wild oats!

You can either dig in a cover crop whilst still green for a quick nitrogen boost to the soil just before planting vegetable crops, like we've been doing recently with the oats or you can slash it and leave it a while until the litter and stubble browns before digging it into the soil as more of a slow release, carbonaceous fertiliser, which we'll be doing prior to planting out our tomatoes in a few months. Green manure crops also regenerate the soils and nourish food crops subsequently planted via their ability to bring to the surface deep minerals. The oats' root depth matches their large leaf size and so they are good for mining the deep soil minerals. The increased soil coverage and types of plants used also provide habitat and food for beneficial insects which in turn reduce the populations of soil and plant pests.  

Our preferred summer green manure is cow pea, which is good for fixing nitrogen into the soil being a legume. It also handles our hot, dry summers better than many other green manure varieties. It grows more thickly with regular rain but is drought tolerant which is handy in what have become dry summers for us. 

The other huge benefit of green manure crops is that over time they out compete and effectively smother weeds, partly by their mere physical presence and partly due to the improved structure and nutrient status of the soil rendering it unsuitable for many persistent weeds to proliferate. This is the other major benefit on our farm...weeds are possibly the biggest thorn in an organic farmers' side and take a lot of time and labour to manage. Our oats are currently doing a great job of suppressing the wild radish and Cape weed which are our major pernicious and persistent weeds!

Recent Posts


Pigs Will Flog Community Blog Snow Food ethics zucchini flowers open pollinated Farmers' Markets culinary herbs roses and herbs relocalisation Swiss Italian heritage new season garlic home grown tomatoes Blakes Feast Catering garlic sales online Daylesford-Macedon Harvest Festival 2011 Angelica Organic Farm cucumbers Winter Warmers Vogue Entertaining and Travel Produce Awards ABC Delicious Produce Awards 2010 Andrew Blake organic farmer Vic Central Highlands Weather organic industry organic garlic backyard poultry Irrigation new season herb bouquets The Chefs Table Cool climate veg growing green manure crop polytunnel garlic braids heirloom lavender farm Tonia Todman GM Foods Corn Dollies rain organic pest control Japanese Mustard Greens Barbara Ross Lake House organic weed managment Heritage Beetroots Andrew Blake, Blakes Feast shallots Fertiliser Australian garlic Melbourne Farmers' Markets bok choi ABC Delicious magazine Rocambole garlic harvest Daylesford Victoria organic tomatoes organic vegetables Genetically Modified Seeds Organic chickens lavender harvest Daylesford heirloom tomatoes Jerusalem artichokes Worldwatch Institute heirloom vegetables eschallots soil preparation heritage tomatoes Golden Shallots bird scarers soil food web garlic bulbs Victorian Farmers' Market Association Accreditation home made preserves autumn produce organic farmer, website, blog, sharing GE foods garlic plaits rocket capeweed Monsanto garlic harvesting Christmas 2009 Angelica Organics blog sharing mesclan salad Summer produce Joel Salatin website Spa Country Matt Wilkinson zucchinis Boroondara Farmers' Market garlic update VFMA Angelica Pope Joan cafe old fashion tomatoes Lavandula Sunflowers Ethical eating seedlings seed raising mulching Compost Blumin Spring