Considerations for a Potential Wet Year

The prolonged drought has increased the media buzz of the predicted El Nino. Although weather data suggests that it may be a strong pattern, it still doesnt mean automatic relief for the California water situation. In saying this, however, there stands a good chance that we will receive average rainfall, which means that things may be wetter through the winter months.

Winter sanitation, planting, and orchard maintenance are easier when it is dry. Operations can move quickly since the days are nice and orchards are accessible. If it rains frequently, however, these operations may be hindered. So whats the back-up plan?

Orchard sanitation. Weather assists with the various practices of orchard sanitation. Storms help remove leaves and mummies from the tree. Furthermore, rain helps degrade mummies once they are on the ground, reducing over-wintering populations. Trees are also easier to pole, which may have to be an option if heavy shaker equipment cannot be used for concerns of compacting wet soil. If possible, once harvest operations are completed, it may be best to begin winter shaking once a few rain events have occurred. Even if this doesnt remove every mummy, it will make it easier on poling crews.

Planting and replanting new blocks. Wet winters can be highly problematic for planting new orchards. Soil preparation is difficult in wet conditions as too much equipment work will compact the soil, creating future issues with infiltration and tree growth. Fields need to be ripped, backhoed, or slip-plowed in dry soil, prior to rain events. Rain that falls after the modification is performed will help with settling. Post-modification leveling and disking should occur after some rain, but before the fields are too wet. Prior to planting, land may need to be disked again due to settling, and berms should be pulled as soon as it is feasible.

Planting trees can be a challenge in wet years. Machine planting in clay containing soils may not be a good idea as the soil may form clods, creating air pockets. Hand planting will also be more challenging as the soil will be heavier. Crews often want to work fast as they are often paid piece-meal, so smaller-than-ideal planting holes may be dug. This may create issues with root-girdling or j-rooting. Do what it takes to make sure trees are being planted properly. Also, tanking in trees is a must when planting in wet soils. Although this may seem counter-intuitive, wet soils tend to form clods, which increase the number and size of air pockets. Applications of 4-5 gallons of water will help remove these pockets. This is an important step – this past year I observed nearly 500 trees die due to the farmers unwillingness to tank the trees in after planting.

Considerations for replanting are greater due to the extra step of soil fumigation. Although we have had success in fumigating soils in the middle of cold down pours, this is not ideal. Too high of soil moisture reduces fumigant movement and can also breakdown fumigants. Sandier soils (e.g. true sands, loamy sand) will be easier to fumigate in wet conditions than loams or clay containing soils.

Other orchard maintenance operations. Irrigation system and pump maintenance as well as pruning needs to occur between post-harvest and bloom. Perform any type of pruning schemes as soon as harvest is completed. Try to prune young trees when there is no rain in the immediate forecast. Young trees can be pruned as late as full leaf expansion without any impact on tree growth. For irrigation and pump maintenance, time will have to be scheduled when there is a break in the weather. Thankfully, if enough winter rain is received, pump time should be less because of reduced leaching requirements/winter recharge, and first the spring irrigation may be delayed a few weeks from wet soils and rain.

Although the drought has forced many to remove cover crops, this may be a good year to re-establish the planting. Cover crops help reduce compaction by increasing structure and helping to reduce soil moisture. This provides the ability access the orchard earlier after a large rain event – which is critical around bloom. It will also reduce sediment run-off. Cover crops should be seeded in the early fall once adequate soil moisture is present.

Although we cant predict the rain, we can implement strategies to help manage the impact of rain on our operations. Think ahead, develop a back-up plan, and hope that the rain does begin to fall.

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