|
| Plowboy & Jon S,
We have on various occasions raised 50 - 70 bu/a soybeans (dryland) on fields with pH of 4.7 to 5.4 (and the higher pH fields didn't yield any better that I've noticed). One field with pH 4.7 has had a lime plot in it for 8 or 9 yrs, and I've never seen a visual difference between any of the subplots, including zero and 2X rate. Measuring soybean yield comes up with negligible differences. I know of several similar plots in KS and Oklahoma with similar results for wheat and other crops. I realize that pH below 5.4 is getting rather scary for crops such as soybeans, but so far no major responses are showing up (part of this may be due to more alkaline subsoils in this part of the world).
Jon S,
Some textbooks are outdated on this. At one time, a neutral pH was considered optimum, but was basically conjecture and not substantiated by hard evidence. Many modern textbooks and soils labs have gradually backed away from that position and are now rather conservative in their lime recommendations. They may not be conservative enough based on what I've seen (again, this may be a regional thing, or maybe varieties have been bred for better adaptation to low pH).
As for that famous graph showing nutrient availability by pH, again, that was speculation. It is a relic from the early 1900s (I forget who came up with it originally), and has been disproven many times (again, newer textbooks have much better graphs depicting nutrient availability by pH, with notations about what chemical reactions are occurring to make the nutrient unavailable, and this very much *is* affected by soil type, i.e., geography). There are reports from North Carolina that liming a soil from upper 4s to low 5s caused severe zinc deficiency. This is a more common phenomenon than people realize.
Liming has been touted by some people/companies as the secret to unlocking soil nutrients. There is a tiny bit of truth in there, but it is greatly overblown.
| |
|
Lime application
