The Yield

The Government Department responsible for advising on corn growing in my region suggests the following:

Recommendation 1: use between 500 and 700 mm of irrigation

I applied 172 mm washing machine water
There was also 282 mm of rain during the crop (with 120 mm coming in just 2 days much of which ran off the surface). That makes a total (irrigation plus rain) of 454 mm.

Recommendation 2: Apply 200 kg N fertiliser (50 kg at planting, 120 kg at 3 weeks and 30 kg at 5 weeks).

I applied no fertiliser or manure at planting. I measured 500 ppm nitrate in the deeper wetting front detector one week after planting. Using calculations I will not give you here – that means I already had more than 200 kg of N in the top 60 cm of my soil. But I did apply 10 kg N/ha at both weeks 4 and 7. Total N fertiliser application 20 kg/ha.

Recommendation 3: Expect a yield of 12 to 22 t/ha of fresh corn (in husk)

My yield was 22 t/ha but some of the cobs were not properlly filled with kernels (the second ones on the plant), which dropped the marketable yield to 20 t/ha

My conclusion:
Good yield with not much water and very little fertiliser.

But wait till you see what the washing machine water did to the soil pH and the level of phosphorus!

Actually I’m monitoring the adjacent bed which was planted one month later. I’m using a pure sodium chloride solution – to the same electrical conductivity as the washing machine water - and getting very different results.

More soon….

The Harvest

For the last two weeks we have been eating the corn. By next week I'll be able to give you total yield and water use.
There are no other graphs this week because I did not irrigate.
More data is coming including the change in soil pH and phoshorus levels over the past 3 months

Week 11: Salt

By now I expected the salt to be in the red zone. I'm wrong

Week 11 Nitrate

Very little nitrate detected at 20 and 40 cm depths

Week 11: Water

The 60 mm of rain in week 11 has wet the top soil again.

This is the week where I ran out of time to look at the data. And this is also the time the logger decided to stop working. You will see next week that there will be several days of missing data.

There is a lesson here. I collect lots of data from lots of places and usually have too much information to make sense of it all. Add to this the inevitable hardware breakdowns and we have information overload plus information gaps = wasted opportunities.

The point is that the effort in monitoring (time and expense) must be matched by the amount I am learning. If I can't turn the information into better decisions and a deeper understanding of the system I'm managing then .....

Week 11: Irrigation

Another wet week. 60 mm over 3 days got a response from both detectors. No irrigation was required.

Week 11: The Crop

Close watchers of this blog will note that this post is almost a week late. The whole idea of a blog is to let the experiment unfold in real time, so we can see the data together and so that I can explain (justify) the decisions I make. Last week I got too distracted and ran out of time. As you will see later - there is a price to pay for this!

The crop is almost ready to be picked.

Week 10: Salt

Before the experiment started I produced the axes of the graphs with the green, orange and red shading. This was to give you some idea of what I expected to happen. I expected the salt to get up into the orange and maybe the red and then I would leach it out. But it did not happen that way. But stay tuned.....the story is not over yet.

Week 10: Nitrate

I collected water samples from both 20 and 40 cm detectors this week. The nitrate has gone. I'll never know how much was taken up by the crop and how much was leached in the rain. But I am confident I managed the system as well as I could to give the crop the best chance of getting the deep nitrate out of the soil. It is why I gave the small irrgations and let the topsoil dry out on weeks 6, 7 and 9.

Week 10: Water

The soil got very wet after all the rain in week 8. In week 9 I only irrigated till the 20 cm detector responded. We cannot see the week 9 irrigation (11 mm) on the water graph - the soil just keepos getting drier. That is why I did the big irrigation this week until the 40 cm detector responded. Now the top soil is fully wet again.

Week 10: Irrigation

This week I decided to keep irrigating until both the 20 cm and 40 cm detectors collected a sample. This required 34 mm, which was 1.17 times the potential evaporation for the week.

Week 10: The crop

Hopefully the kernels are filling inside the cob.

Week 9: Salt

After lots of rain, this time I do not expect to find a lot of salt!

Week 9: Nitrate

The small irrigation was just enough to activate the detector at 20 cm depth - and there is very little nitrate at this depth.

Week 9: Water

The 125 mm of rain during week 8 got the soil totally wet, but the topsoil is drying down quickly. The 11 mm of irrigation applied this week apparently did not reach the sensor at 30 cm depth.

Week 9: Irrigation

After all the rain during week 8, I decided on a small irrigation for week 9 - only 11 mm or 0.36 of potential water loss. This was just enough to activate the detector at 20 cm depth. I irrigated because my soil sensor at 30 cm depth showed the soil was already getting dry - but I wish I had a water sensor in the sub soil.

Week 9: The Crop

The corn still looks OK

Week 8: Salt

I thought 125 mm of rain would wash all the salt away. Not so - the salt is still there, but as I've said each week it is not as high as I expected it to be. It was obvious during the rain that water had trouble infiltrating into the soil. Water ran off the beds into the furrows. It took two days and 100 mm of rain before the deeper detector collected a sample. In other parts of the garden, detectors at the same depth responded with half that amount of rain. Clearly the salt in my washing powder is changing the soil structure.

Week 8: Nitrate

I applied the same amount of nitrogen fertiliser on week 7 as I did on week 4. But there was no sign of the added nitrate in the shallow detector (green). But there is stacks of nitrate at 40 cm depth (red).

Week 8: Water

With all that rain, the soil is now fully wet. The corn is particularly sensitive to water stress during silking and pollination. There will not be a problem this year!