November 23, 2017
Trials Highlight Relative Organic Manure Value
Organic manure can give significant improvements in soil health and productivity in a relatively short time, confirms the latest Agrii research. But the type and scale of the improvements is likely to vary widely between different manures, making it important to employ the right manure for both the conditions and the task in hand.
Five different manuring regimes were examined at a field scale on silty clay loam ground over four seasons at the AgriiFocus Technology Centre near Marlborough in Wiltshire. The fully replicated treatments of chicken manure, biosolids, farmyard manure and green compost were applied and incorporated to deliver exactly the same levels of total nitrogen/year within RB209 guidelines. A double rate of green compost was also included.
After three applications in the spring barley/winter OSR/winter wheat rotation, most treatments gave clear increases in bread wheat yields. Subsequent measurements of organic matter levels, earthworm populations and infiltration rates also showed noticeable improvements in most cases. However, the treatments giving the greatest yield increases were not necessarily those improving the key soil health indicators to the greatest extent.
“From an untreated average of 2.7%, the most impressive soil organic matter improvement – to well over 4% – came from our double rate of green compost addition (150 t/ha in all over four seasons) reported Agrii trials manager and agronomist, Dr Syed Shah at a special soil health briefing.
“A total of 30 t/ha of chicken manure over the trial boosted the average OM to just under 4% while 60 t/ha of biosolids only increased the level to just over 3%, 75 t/ha of compost to around 3.25% and 120 t/ha of FYM to just over 3.5%.
“The higher rate compost and biosolids treatments also gave the most significant increases in earthworm populations – from an untreated average of just over 80g/m2 to around 150g/m2 and 130 g/m2 respectively. FYM and standard rate compost did a similar job to biosolids here. But chicken manure actually reduced the earthworm population to around 70g/m2.
“FYM gave us by far the best wheat performance, though,” Dr Shah pointed out. “Averaged across in crop fertiliser nitrogen rates it raised Gallant yields from around 10.45 t/ha to almost 11.55 t/ha.
“The double rate of compost delivered 11.15 t/ha, poultry manure 10.77 t/ha, the standard rate of compost 10.61 t/ha and biosolids 10.23 t/ha.”
The performance superiority of FYM in the Agrii trials was underlined by the fact that raising in-crop fertiliser N rates from 160 kg/ha to 260 kg/ha gave little or no yield increase compared to 0.5-1.5 t/ha recorded with the untreated control and the other manuring regimes.
While all the treatments improved water infiltration rates, FYM also proved noticeably better than the other manures in this respect.
These results underline how much more there is to improving arable performance through organic manuring than just improving the key soil health indicators of organic matter levels, earthworm populations or infiltration rates.
“We need to think more broadly here,” suggested Dr Shah. “There may be more carbon in green composts and chicken manure but they aren’t nearly such good food sources for soil micro-organisms as FYM. And the acidity of chicken manure is quite obviously a negative factor as far as earthworms are concerned.
“The straw in FYM is good for soil structure and drainage and may also be making a valuable addition to potash levels. Biosolids, on the other hand, can be useful in increasing phosphate indices.
“Our trials clearly underline the value of organic manuring in improving the health and productivity of arable soils for the greatest cropping resilience. Which manures are best is very much matter of horses for courses as well as local availability and relative cost.
“FYM will almost certainly be the best choice where your priority is across-the-board clay-based soil health and productivity improvement,” he advised.
“On sandy soils where increasing the infiltration rate is undesirable you’d be better off using compost, which also has a particular value in improving trace element status. It’s relatively high volume makes compost useful as a surface mulch for black-grass control too.
“Biosolids can be especially valuable where you want to improve phosphate indices. And chicken manure is probably best on high pH soils.”