Growing Plants in Straw Bales

Plants do not need soil, as we all know from the fact of hydroponic cultivation,a  kind of culture which involves an inert growing medium enriched by a liquid nutrient solution which contains all the nutrients necessary for the plant to thrive. It is not as good as soil, as plants benefit from a symbiotic relationship with mycorhizal soil fungi to thrive, but they do succeed without it. But there are alternatives to hydroponic cultivation, for example straw. Straw [not hay] bales are a useful growing medium that provides an environment in which a wide range of plants may be grown, and as they rot they  provide the plant with a steady supply of nutrients to augment the fertilizer applied to them. 

The advantages of straw bales are several. One is that they can be laid on a stone/paved surface. Sometimes they are encased in wooden containers to make what appears like a raised bed. In fact, containers are advantageous as the bale breaks  down over the year and is quite crumbly at the end of the process, so the wooden sides keep it together. But this friability is an advantage, as the decayed bale can be turned into garden compost and used to fertilize beds. Furthermore, you cannot over-water bales, as the surplus water simply comes out at the bottom. Moreover, they are non-combustible, as straw is not a fire hazard. 

Hay bales can be used, but their disadvantages outweigh their advantages. Hay bales can sag as they rot, and while they provide more nutrients than straw does,they often contain grass seeds , which flourish in the bale and need to be weeded out. Hay is also combustible, as farmers have sometimes found it to their cost when a haystack ignites. 

You will need to know the technique of straw bale cultivation. Firstly, it is desirable to place the bale on a hard surface, sometimes this can be paving stones, but some growers place the bales on a tarpaulin or geotextile. The advantage is that weeds cannot grow through the tarpaulin to infect the bale. 

I am now going to explain fertilizers, with apologies to those of you who know already.When reading the list of contents you see three numbers, for example 23:10:16.  These stand for N:P:K, nitrogen,phosphorus, potassium:  The bale should have  a high nitrogen fertilizer applied, e.g. 27:2:8. This should be spread across the top of the bale and the water applied in a gentle stream to avoid washing off the fertilizer. Gently water until the water begins to flow from the base of the bale The amount of fertilizer should be about half a cupful. The next day the bale should be watered as it was the previous day.At this point the bale's temperature should be taken. As it is decomposing it should be about 45 C. 

I would also apply seaweed meal of liquid seaweed, as this is a useful source of micronutrients, which conventional N:P:K fertilizers are not. 

The procedure should be repeated. On the third and subsequent odd numbered days apply water and fertilizer as on day one. On even numbered days just add water.  On day 10 add a balanced fertilizer, e.g.12:12:12 and continue watering. On day 12 if the temperature as dropped below 45 Celsius you can begin to plant.    

If you are using organic rater than chemical fertilizers, ensure that the doses of fertilizer are about 25% larger than the non-organic quantities that I have prescribed, as organic fertilizers tend to be less nutrient intense than non-organic ones. Regular feeding with fertilizer every few days is necessary, but only give the same dose as you gave in the first twelve days outlined above. But stick to an equally balanced N:P:K. compost, such as 10:10;10. You do not need the high nitrogen fertilizer at this stage, as the rotting that it produces has been well-started.  

However, there is  the matter of the planting medium. Some growers apply a coating of soil or compost about five centimetres deep across the top of the bale, but others scoop out planting holes and fill with soil. Some use an alternative to soil, such as vermiculite or other soil-less medium, and then continue to add fertilizer. As the bale rots the plants will feed on the rotting straw.   

Anything other than a tree or a bush can be grown on a bale. Plants that produce their edible sections above ground are easy. Thus peas and beans, cabbages, salad crops,pumpkins,and marrows for example are prime candidates for straw bale cultivation. Sweet corn will send its long root down into the depths of the bale to absorb nutrients. Onions and leeks also root shallowly and produce near crops to the surface, so there are no problems. Potatoes, parsnips and carrots,all root vegetables, can also be grown, for they are able to push down into the decaying straw.  However,if you grow members of the Brassica family [cabbages, kale, cauliflower, broccoli, sprouts calabrese,turnips] you will need to add some lime, as this family requires a pH higher than other vegetables do, so if you do want to grow a range of vegetables,different straw bales for vegetables with difering requirements might be a good idea. 

Some plants require staking, such as beans, and this can cause a problem, as stakes cannot be easily  driven into a straw bale. The solution can be to fix stakes into the ground near the bale and fix the plants to them. This is likely to be the case with beans, peas and marrows. If the ground is too hard placing the bale near a mesh fence allows the plants to be tied to the fence 

Certain vegetables are greedy feeders, such as pumpkins,so they will need a large dose of fertilizer. But the up-side of this is that members of the pumpkin family are well suited to straw bale cultivation. One large pumpkin per bale can be quite a nice little project that can allow you to specialize with different plants for different bales.

Herbs and salads can have the soil spread  a few centimetres deep  across the top  of the bale, and  these two kinds of easy-to grow-vegetables will happily thrive. However,  some, especially root crops, will benefit from a small compost filled hole specially dug out of the straw surface into which the seedling can grow. Potatoes, especially,require some depth of soil and an application of manure,or failing that potato fertilizer. The manure applied can be in the form of liquid manure  or pelleted manure, which can be purchased from garden centres and a variety of other outlets. Compost can also be liquidized and applied to the bale. 

There is an issue that has yet to be resolved, which is how well to different kinds of straw fare in straw bale cultivation. More research is needed, but wheat straw seems to be popular. However, it depends upon the cereal most grown in your locality. In my area barley is dominant.

There is also the issue of safety. Straw bales are heavy, and it is possible to strain your back sifting them. Don't overstretch yourself,  and when you are laying them seek assistance. At sixty five I know that while I am still strong, there are garden tasks in which I need, or at least benefit from, the aid of my thirty four year old eldest son.  

However, do not think that you will always be free of weeds, for there are airborne weed seeds, and what grows  from them needs to be eradicated. Often you find small mushrooms growing. You have to be careful about eating wild mushrooms, but inkcaps, which commonly flourish in nitrogenous waste, are not poisonous. But beware, glistening inkcaps contain antabuse, so taking them with alcohol causes physical problems for a few hours. But mushrooms can be composted. A basic rule for mushrooms is "play safe and if you are unsure do not eat."

The bale will survive a year, but towards the end it will be disintegrating. When the growing season is over, compost it and use the resulting compost on the beds in your garden.

Straw bales are useful for cultivation on a hard surface, and they can be used to grow on a worn out patch of land while it is refreshing. It does not replace conventional gardening, but supplements it,adding to the rich repertoire of the gardener's art.