There are 20 essential nutrients necessary for complete plant growth and development. Not all are required for all plants, but all have been found to be essential to some. Three of the 20 (carbon, hydrogen, and oxygen) and are derived from CO2 and H2O and are not usually considered in terms of managing a plant nutrition and soil fertility program.
The remaining 17 are commonly referred to as mineral nutrients (N, P, K, Mg, Ca, S, Fe, Mn, Mo, Cu, B, Zn, Cl, Na, Co, V, and Si). Of the 17 mineral nutrients, N, P, and K are the macronutrients; Mg, Ca, and S are secondary nutrients; and Fe, Mn, Mo, Cu, B, Zn, Cl, Na, Co, V, and Si are referred to as micronutrients. The terms macro-, secondary, or micronutrients do not refer to any level of importance but rather to relative amounts required by plants.
The amount of a given nutrient found in a plant will depend on several; factors, governed in general by a broad range of plant and environmental interactions. The percentage composition of plant nutrients can vary considerably among species and locations. Since all the mineral nutrition is provided to the plant by nutrient uptake from the soil through the root system, an understanding of the soil conditions and the effects on plant nutrition are very important.
There is usually a rather poor relationship between the total amount of a given nutrient found in the soil (i.e., P or K) and the amount available to the plant for uptake and utilization. This is certainly true in Arizona where our agricultural soils are commonly rather young (geologically) alluvial soils with a high native fertility level.
Soil tests are commonly used to establish a relationship between an estimated level of a “plant-available” form of a given nutrient and its sufficiency, deficiency, or toxicity for the crop in question. The relationships between a soil test and actual crop nutrient needs are usually specific for a crop and region and a set of common soil conditions.
Developing a sound fertilization program begins with a good understanding of actual soil conditions. The collection and analyses of a good(representative) set of soil samples and then relating that information to established guidelines are the first steps toward developing a strong soil fertility and plant nutritional management program for any crop. This is important for the overall efficiency of a crop production system, including agronomic, economic, and environmental efficiency.
To maximize nutrient management efficiency, it is good to consider the 4R concept of plant nutrient management and application, consisting of:
1. Right fertilizer source at the
2. Right rate, at the
3. Right time and in the
4. Right place
The 4R nutrient stewardship approach utilizes the implementation of best management practices (BMPs) that optimize the efficient use of fertilizer by the crop. The primary objective of the 4R approach and BMPs is to match nutrient supply with crop requirements and to minimize nutrient losses from fields. Each case can vary among farms and fields, dependent on local soil and climatic conditions, crop, management conditions, and other site-specific factors.New automated/robotic ag technologies are coming out all the time. Ever wonder how they function in the “real world” and whether they are cost effective? Western Growers recently released a case study report on the economic impact of Stout Industrial Technology, Inc.’s Smart Cultivator on overall weeding costs. The study tracked expenses, productivity, and labor savings of the machine operating over one year on five types of lettuce crops and 2,700 acres at Triangle Farms in Salinas, CA. It is a well done, detailed study with machine costs and labor savings broken down by crop type and acreage. It’s an easy read and worth the time for those interested in the economic and overall feasibility of automated mechanical weeding. Check it out here or by clicking the image below. I don’t want to be a spoiler, but I was surprised to learn that costs for hand weeding lettuce in Salinas, CA were so high - $525/acre (conventional) and $750/acre (organic) and that in these conditions, the return on the $330K investment for the machine was less than one year when used on 2,700 acres.
Stay tuned. Western Growers plans to release four more automation technology case study reports within the next year. Upcoming reports include grower case studies experiences with the automated weeding machine from Ecorobotix; and with autonomous ag platforms from Burro, GUSS Automation, and Bluewhite. Their first report, which examined the economics of Carbon Robotics’ Laser Weeder at the commercial scale, can be found here.
Fig. 1. Western Growers case study report on the economic impact of Stout Industrial
Technology, Inc.’s weeding machine on weeding costs in lettuce on 2,700 acres at
Triangle Farms, Salinas, CA. Click here or on the figure to view. (Photo credit: The
Western Growers Centerfor Innovation & Technology)
This inquiry has been brought to us for different herbicides; How much time does this product require to safely plant lettuce?
Of course, this depends on many variables such as the management done in the crop before lettuce, texture, water applied, rate, climatic conditions presented, and many other factors.
The following table published in this Newsletter by Barry Tickes can serve as a general guideline to base Integrated Pest Management decisions and program our strategies. It’s always recommended to check the label for the product used in previous crops.
As the intense heat of the Yuma summer finally fades, cooler days bring the promise of lush fields which set the stage for a vibrant growing season. However, the cooler weather also signals the arrival of seasonal pests, ready to take advantage of your organic fields. These pests tend to have an especially strong appetite for organic crops, making it essential to stay vigilant. Thus, it is important to implement appropriate IPM techniques to combat these insect pests effectively. It is crucial to plant resistant varieties, scout regularly, ensure your crops are healthy, diversify your crops, use physical/mechanical control, enhance biological control, or apply biopesticides when necessary.
Remember, some IPM tactics may be unsuitable in some situations because IPM is not a one-size-fits-all. Therefore, an IPM program should be planned on a case-by-case basis.
Both organic and conventional lettuce are high-demand crops for nitrogen, with organic lettuce requiring organic nitrogen and conventional lettuce requiring general nitrogen sources. Lettuce requires a substantial amount of nitrogen to support its growth, particularly during the heading stage when most nitrogen uptake occurs. This demand is driven by its rapid growth rate and the production of large leaf biomass.
Organic nitrogen/nitrogen management for lettuce production in Yuma, Arizona, is acritical aspect of efficient and sustainable agriculture. Proper nutrition(organic nitrogen or nitrogen) management can improve crop yield, reduce environmental impact, and optimize resource use. This is significantly correlated with sufficient soil moisture availability. As a result, improper or excessive water and nutrient management for both organic and conventional lettuce production systems could significantly and negatively impact growth, development, and yield quality.
Moreover, several studies have reported that proper water and nitrogen management could potentially reduce aphid attraction to lettuce, as aphids are more prevalent in lettuce with higher nitrogen content. Elevated nitrogen levels in lettuce can attract and support larger aphid populations.
There are many approaches that could be adopted for coupled water and nutrient management, or in other words, best management practices to avoid excessive or inadequate application of either element. After soil sample analysis in the pre-season, one of these approaches involves utilizing high-tech site-specific sensors, which can be installed between two healthy plants that represent the majority of the field to monitor nitrate-N levels in the soil throughout the growing season. These sensors monitor nitrate-N levels on a daily or weekly basis to evaluate nutrient levels at different soil profile depths, especially during critical lettuce growth stages. Many studies have reported that site-specific, sensor-based nutrient management increases efficiency compared to traditional methods, resulting in significant nitrogen savings.
Preliminary results from ongoing research comparing nutrient levels by utilizing AquaSpy Nitrate sensor (Figures 1. 2. And 3) with soil analysis conducted in the lab (Ward Laboratories Inc.) as part of the study on organic vs. conventional iceberg lettuce under subsurface drip irrigation at the Yuma Ag Center-Valley Research Center, suggest that the findings are comparable to a considerable extent so far. Soil moisture availability and soil temperature fluctuations significantly influence the data reflected by the sensors, particularly at varying profile depths. This is an ongoing project; however, the results are promising regarding the aforementioned objectives in organic and conventional lettuce production systems. Stay tuned for the results and conclusions after harvesting.
Figure 1. Nitrate sensor from AquaSpy was installed between two healthy plants in the
organic lettuce production field at the Valley Research Center at the University of
Arizona, Yuma Agricultural Center, Yuma, Arizona.
Figure 2. Nitrate level in the conventional lettuce production field at the Valley Research
Center at the University of Arizona, Yuma Agricultural Center, Yuma, Arizona.
