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Los huertos de pistacho tienen árboles machos y hembras. Tenga en cuenta el árbol masculino en la parte delantera de la foto con árboles femeninos que llenan la fila detrás del macho. Foto por: Elizabeth J. Fichtner, UCCE Tulare County

 

Por: Elizabeth J. Fichtner, UCCE Condado de Tulare

Desde mediados de marzo hasta mediados de mayo, los residentes de Ivanhoe pueden notar que el polen emana de los huertos locales y deja una fina capa de polvo en superficies como los automóviles. Las personas con alergias estacionales pueden ser muy conscientes del recuento de polen, como se anuncia en las aplicaciones meteorológicas. El polen arrastrado por el viento de cuatro huertas en el condado de Tulare, todos cultivados cerca de Ivanhoe, es en parte responsable tanto del polvo como de la alergia. El pistacho, la nuez, la nuez y el olivo son cultivos locales polinizados por el viento que florecen en primavera, pero su floración puede pasar desapercibida debido a la falta de flores vistosas.

La floración del nogal, el pistacho y la nuez pecana es algo discreta en comparación con la espléndida y vistosa floración asociada con los almendros y otros cultivos de frutas frescas. Las vistosas flores asociadas con las almendras, las cerezas y los melocotones están adaptadas para atraer a las abejas polinizadoras necesarias para la polinización cruzada de los árboles. Los cultivos polinizados por el viento no dependen de los insectos y, por lo tanto, no dedican tanta energía a producir hermosas flores. Debido a que dependen de la dirección aleatoria del viento para transportar el polen, cada flor masculina produce una gran cantidad de polen. Luego, la planta depende de la deposición exitosa de un pequeño porcentaje de ese polen en las partes de las flores femeninas. La nuez, el pistacho y la pacana producen flores masculinas y femeninas separadas. La pacana y la nuez se reproducen de manera similar, con flores femeninas y masculinas (llamadas amentos) que nacen en el mismo árbol. Los huertos de pistachos contienen árboles machos y hembras. Los árboles machos solo sirven para producir polen y no producen nueces.

Las aceitunas producen uno de los tipos de polen más alergénicos. El condado de Tulare, sin embargo, tiene la mayor superficie comercial de aceitunas en California, y el polen, aunque alergénico, es necesario para establecer la cosecha de $30 millones.

A medida que los árboles de hoja caduca brotan, los productores están ocupados aplicando aerosoles foliares que generalmente incluyen micronutrientes. Las hojas jóvenes que están presentes justo después de la brotación son más capaces de absorber los nutrientes aplicados por vía foliar que las hojas más viejas, por lo que el momento de estas aplicaciones es fundamental para que los productores obtengan el mejor rendimiento económico de la inversión en fertilizantes. Los productores también controlarán las malas hierbas que han crecido en el suelo del huerto durante el invierno lluvioso. El nitrógeno a menudo se aplica a la superficie del suelo aproximadamente un mes después de la floración, cuando el suelo se ha calentado lo suficiente como para promover la actividad de las raíces. Los productores están monitoreando activamente las plagas y enfermedades y están atentos a las anomalías que puedan ocurrir como resultado de la intensa lluvia en la primavera.

Actualmente, gran parte de la superficie de los huertos se encuentra en varias etapas de remoción. Algunos huertos están programados para la remoción, pero la demanda de servicios de remoción de huertos excede la maquinaria disponible para estos trabajos. La eliminación generalizada de huertos no está relacionada con enfermedades de las plantas, sino más bien con una adaptación a los cambios en los factores económicos y regulatorios que afectan la agricultura. Nuestra tierra agrícola local puede cambiar un poco hacia los cultivos anuales, por lo que las decisiones de plantación se pueden tomar año tras año en función de la disponibilidad de agua.

Aunque la floración de la nuez, la pacana y el pistacho puede no ser tan llamativa, estos árboles producen un hermoso dosel a medida que se abren. A medida que avanza la primavera, disfruta viendo cómo se expanden los brotes y las hojas, produciendo áreas sombreadas en nuestro paisaje abierto y cálido, mientras proporciona alimentos nutritivos para nuestra comunidad y el mundo.

 

Pistachio orchards have both male and female trees. Note the male tree in the forefront of the photo with female trees filling in the row behind the male. Photo by: Elizabeth J. Fichtner, UCCE Tulare County

 

By: Elizabeth J. Fichtner, UCCE Tulare County

From mid-March through mid-May Ivanhoe residents may notice pollen emanating from local orchards and leaving a fine layer of dust on surfaces such as cars. Those with seasonal allergies may be hyper aware of the pollen count, as advertised on weather apps. The wind-blown pollen from four orchard crops in Tulare County, all grown near Ivanhoe, are partly responsible for both the dust and the allergy distress. Pistachio, walnut, pecan, and olive are all local wind-pollinated crops that bloom in spring, but their bloom may go largely unnoticed due to a lack of showy flowers. 

The walnut, pistachio, and pecan bloom are somewhat understated in comparison to the splendid showy bloom associated with almonds and other fresh fruit crops. The showy flowers associated with almonds, cherries, and peach are adapted to attract the honey bee pollinators required to cross-pollinate the trees. Wind-pollinated crops do not rely on insects, and therefore do not put as much energy into producing beautiful flowers. Because they rely on the random direction of wind to transport pollen, each male flower produces a tremendous amount of pollen. The plant then relies on the successful deposition of a small percentage of that pollen on female flower parts. Walnut, pistachio, and pecan all produce separate male and female flowers. Pecan and walnut reproduce similarly, with female and male flowers (called catkins) borne on the same tree. Pistachio orchards contain male and female trees. The male trees serve only to produce pollen and do not produce nuts. 

Olives produce one of the most highly allergenic types of pollen. Tulare County, however, has the largest commercial acreage of olives in California, and the pollen, albeit allergenic, is necessary to set the $30 million crop. 

As deciduous trees leaf out, growers are busy applying foliar sprays which generally include micronutrients. The young leaves that are present just after bud break are better able to absorb foliar-applied nutrients than older leaves, so the timing of these applications is critical for growers to get the best economic return on the fertilizer investment. Growers will also be managing the weeds that have grown on the orchard floor through the rainy winter. Nitrogen is often applied to the soil surface approximately one month after bloom, when soil has warmed enough to promote root activity. Growers are actively monitoring for pests and diseases  and are keeping a watchful eye for anomalies that might occur as a result of the intense rain in the spring.

Currently, much orchard acreage is at various stages of removal. Some orchards are scheduled for removal but the demand for orchard removal services exceeds the machinery available for these jobs. Widespread orchard removal is not related to plant disease but rather an adaptation to changes in the economic and regulatory factors impacting agriculture. Our local agricultural land may shift somewhat toward annual crops so planting decisions may be made on a year-to-year basis based on water availability.

Although the bloom of walnut, pecan, and pistachio may not be as showy, these trees produce a beautiful canopy as they leaf out. As spring progresses, enjoy watching the shoots and leaves expand, producing shady areas in our otherwise hot and open landscape while providing nutritious food for our community and world. 

 

La remoción de toda la huerta es más común durante los meses de invierno. Foto cortesía de of Elizabeth Fitchner.

A medida que llegan los meses de invierno al sur del Valle de San Joaquín, muchos cultivadores de nueces están terminando sus cosechas y preparándose para la próxima temporada de cultivo. Con el final de la cosecha de almendras, pistachos y nueces, la maquinaria de cosecha ha dejado el campo y el polvo se ha asentado, literalmente.

Whole orchard removal is most common during the winter months. Photo courtesy of Elizabeth Fitchner.

A UC agricultural advisor explains the harvest cycle, soil amendments

By Elizabeth Fichtner, Agricultural Advisor, UCCE Tulare County

As the winter months arrive in the southern San Joaquin Valley, many nut growers are wrapping up their harvests and getting ready for the next growing season. With the end of almond, pistachio, and walnut harvest, the harvest machinery has left the field and the dust has settled—literally.

You might still see one nut crop being gathered. Pecans are the last of the nut crops to be harvested, and their late fall harvest proceeds more slowly than that of other nut crops, namely because they are harvested after the start of the rainy season when wet ground makes it more difficult  to drive into orchards. As a result, pecans are often harvested into December, while the other nuts are harvested by the end of October.

During the dormant season, growers are busy preparing orchards and land for the following year. Trees are pruned to remove dead or diseased wood and to improve light interception in the canopy. Less productive orchards may be removed to prepare the ground for replanting with another crop, or to fallow land to reduce groundwater use. Upon pushing over the trees, the remaining wood is either chipped and reincorporated into the orchard floor or burned. Burning is less costly than chipping and is likely to get rid of pests and diseases associated with the wood. The downside of burning is the adverse effect on air quality. Consequently, burning operations are both limited and regulated, and growers must receive permission to burn orchard debris from the Air Pollution Control District. Mixing chipped wood into the soil has its own advantages such as improvement of soil structure and fertility.

You might also see big piles of what looks like chalk dust at the edges of orchards. This is the time of year that most soil amendments are applied to the orchard floor. Inorganic materials, such as sulfur (yellow) and gypsum (white), are often applied during the winter to allow the products to mix with water  and enter the soil profile. Because soils in this region are generally calcareous (high pH), sulfur is used to acidify the soil. Gypsum is a source of calcium and is added to improve water penetration, ameliorate salinity, and provide plant nutrition.

Dormant season in a walnut orchard. Photo courtesy of Elizabeth Fitchner.

Have you noticed piles of  compost applied to orchards? You’re seeing organic amendments that are applied to the soil as a source of plant nutrition. Because some forms of inorganic nitrogen are readily leached through the soil and may threaten groundwater quality, growers apply compost as a form of slow-release nitrogen that is less likely to enter groundwater than nitrogen applied in inorganic forms. Incorporation of organic matter to the soil also improves water retention and water penetration.

Growers tend to apply compost soon after harvest to maximize the amount of time the material is in the field before the following year’s harvest. Over time, food safety risks associated with microbes in animal waste decrease and organic matter slowly decomposes to release nutrients for plant growth. The decomposition of compost is achieved by soil microbial activity. The microbes actively metabolize the debris, producing heat and carbon dioxide as they respire. On cold winter mornings, the steam arising from the soil surface is evidence of microbial activity.

Although dormant, nut trees in the southern San Joaquin Valley rely on the cold temperatures to produce a crop the following year. Freezing temperatures, however, particularly in the fall, may cause damage to trees, resulting in dieback. As a community, we can appreciate the cool, foggy mornings of winter knowing that the flower buds are preparing for a bountiful season the following year.