August 2022

Managing maize after a drought
Drought-stressed maize creates many challenges for forage and grain growers. This article addresses the questions and concerns that growers face when harvesting maize for silage under moderate to severe drought stress.
 

Expected forage yield

Maize considered for an earlier than normal forage harvest in mid-August may not have any ears. Yield of this immature silage will likely be less than 50% of its original potential. A rule of thumb that can be applied to earless maize is that it will yield about 4 tonnes / hectare per 50cm of plant height. It may become necessary to ensile droughted maize early and quickly to avoid further losses to diseases such as Fusarium. 

Grain typically makes up 45-50% of silage yield
 

Nutritional value of silage

Drought stressed immature maize silage feeds like highly digestible grass silage. Lack of grain leads to no starch – sugars are not converted to starch and remain in the stalks. Sugar content of the forage will be elevated relative to normal mature maize silage and more aerobic instability is likely. Drought stress increases fibre digestibility, so Neutral Detergent Fibre (NDF) digestibility should be relatively high. In general, immature, drought stressed maize silage will provide about 50-70% of the energy value of a normal maize silage. Maize with some ear development will be lower in starch but higher in sugar and protein content.
 

Harvesting for silage

Silage maize with little ear development should be harvested when no further quality and yield development can be expected.                                                                      
Fields with some ear and green leaves around and above the ear can still enable the plant to grow in yield and quality because they deliver assimilates to the ear. Once those leaves start to turn dry, the maize should be harvested.

Decision aid for harvest of drought stressed maize
For successful ensiling, you still need to target dry matter at 32-38%. Lack of starch deposition in the ear helps dry down the entire plant. Even if leaves are completely dead, there can be significant moisture retained in the stalks. Chopping too wet is a real risk that not only puts feed at risk of clostridial fermentation, but may produce silage effluent that must be contained of course given its extremely high biochemical oxygen demand (BOD). The probability of yeast, moulds and mycotoxin activity in droughted maize is heightened, due to the plant stresses that are occurring and the lack of plant defences. Chop length can be increased to reduce effluent but will require close attention to silage compaction.
 

Inoculants for drought stressed maize

Use of an inoculant is more important than ever for drought-stressed silage to further reduce dry matter losses and preserve quality and palatability of the silage. Moisture/dry matter content will likely be variable. Use of a proven inoculant can help, but not eliminate, variation in fermentation that can result from moisture variability. Yeast levels will be higher than normal, and they consume lactic acid, thus increasing the instability of the ensiled forage. High sugar content in immature maize silage makes for increased risk of aerobic stability at feed-out and provides an excellent nutrient source for spoilage organisms to grow.                                                             
High sugar levels in drought stressed maize with limited or no ear production results in higher remaining sugar levels after ensiling, consequences of this are higher yeast activity and heating.

Feed inventories are likely to be tight and minimising shrink is paramount as every tonne of feed will be needed. The recommended inoculant should contain a strain proven to reduce heating such as the L. Buchneri strains  found in Pioneer® brand inoculants 11C33 or 11A44.

  • To prevent heating in the clamp
  • To keep the maize silage cool and mould free

  • Pioneer Rapid React L. buchneri strain establishes aerobic stability from 7 days after harvest
  • L. buchneri inhibits yeast growth to reduce heating in the clamp and during feed out
  • L. plantarum increases efficiency of fermentation limiting dry matter losses resulting from high nitrate levels

  • Not recommended as fibre digestibility will already be very high in droughted maize silage 
Buchneri - infrared thermography from experimental use
 

SAFETY is first

Priority around Silos, the reduction in nitrates via ensiling is because the nitrates are converted to nitrous gas – which is EXTREMELY TOXIC! This heavy gas kills. Extreme ventilation and breathing apparatus are legitimate considerations when working around this early storage silage – especially in enclosed environments.
 

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