Crop4Life biostimulant enhances the mineral nutrient content of oranges

INTRODUCTION

Crop4Life is a non-toxic, comprehensively studied, plant-extract-based biostimulant product sold in South Africa and in some other parts of the world. Although more than 1000 trials have been done on this product, very few of the research results have been made available publicly. In the following weeks, I will start publishing information about the effects the product has on citrus. In my capacity as science lead, I am revisiting the datasets in the R&D database, writing the information up in a standard format (since the research was done by independent contractors, such as myself) and eventually full technical guides, which make available the research data, will be published.

This article gives a short overview of the findings on mineral nutrition in oranges. Mineral nutrients are essential for crop productivity but it also contributes to human and animal nutrition. Macronutrients support the growth and health of plants and are critical to plant life. Nitrogen (N), phosphorous (P), potassium (K), magnesium (Mg), and calcium (Ca) are macronutrients. Plants metabolise micronutrients in smaller quantities than macronutrients and these nutrients often contribute to the quality of yield. Examples of micronutrients are boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) amongst others.

AIM

The aim of these studies was to evaluate the effect of the full spray programme of Crop4Life, three sprays per season, on the mineral content of orange fruit.

MATERIALS AND METHODS

The trial was replicated four times one time at each of four different localities in the Eastern Cape province of South Africa. The localities, cultivars, rootstock and irrigation regime under which the product was studied are indicated in Table 1.

Table 1. Trial number, locality, cultivar, rootstock and irrigation regime of the oranges on which the study was conducted

The treatment application was made as an additional spray to the farmer's standard spraying programs (nutritional, crop protection and others), while the untreated control represented the farmer’s standard spray programme. The treatment, dosage and timing of treatments are indicated in Table 2. Treatments were applied with a motorised knapsack ensuring adequate coverage of the product over the whole canopy. Timing of application was at 100% petal drop, with fruit set and during cell growth and development. These stages fall roughly in October, November and December in South Africa.

Table 2. Treatments, dose and application timings of products sprayed on Palmer and McClean navels?

Commercial trial

Additionally, the effect of the application of the product was tested in the commercial environment on Delta Valencia oranges. The product was also applied at 100% petal fall, at fruit set, and during the early growth and cell division of fruit, roughly during October, November and December on 5 hectares of Delta orange orchards.?

Assessments

At harvest, 20 fruit were collected from different canopy positions in the treated trees as well as in the control trees so to gather a representative sample. The samples were sent to the Accredited Agricultural Laboratory Bemlab in Strand in the Western Cape. Nutrient analysis was done for nitrogen, phosphorus, potassium, calcium, magnesium, sodium, manganese, iron, copper, zinc and boron. Macro elements N, P, K and Ca were measured in mg per 100g fresh mass and micronutrients Na, Mn, Fe, Cu, Zn and B were measured in mg/kg (parts per million).

?Data analyses

Values for the historic decline of nutrients in oranges were obtained from the literature (McCance and Widdowson, 2000). The more recent values (of 1991) were compared to the historic values of 1940. The recent values compared to earlier values by calculating the percentage difference between the values.

To do this, 1940 values are deducted from 1991 values to give a value in which more recently produced fruit differed from the historical fruit. A percentage value was calculated (value "year 1991"- value " year 1940/"value year 1940" *100 = percentage difference). This value then represents the “percentage difference” between the two values.

Similarly, the percentage difference was calculated between the control value and the treated value for each nutrient at each locality. The average values for the mineral nutrients of the four experimental and one commercial trial values were then calculated.

RESULTS AND DISCUSSION

The mineral nutritional value of fresh produce has been declining steadily over the past decades. This also holds true for oranges. Between 1940 and 1991 a decrease in most mineral nutrients in oranges was seen when studied by McCance and Widdowson (2000) (Figure 1; figure drawn from data for oranges as presented in McCance and Widdowson, 2000).?

All values decreased over time except for the values for calcium and sodium. Calcium is routinely added to the production environment, perhaps a practice occurring more commonly in recent years than in earlier days and this may indicate why the percentage of calcium is higher in the newer era. Interestingly, sodium was 72% greater in oranges in 1991 compared to oranges in 1940. This could be indicative of more sodium in the production environment as soils and water become saline due to a lack of water due to climate change.

When comparing the average values for treated fruit to those of untreated fruit, all nutrients in treated fruit were higher than for untreated fruit except for phosphorous which stayed the same and sodium which decreased (Figure 2).

The results of these studies are encouraging from various perspectives. The first is how it could contribute to human nutrition and health - fruit with lower sodium content might prove beneficial for the diets of those who suffer from hypertension. Moreover, it presents evidence that the nutrients that were provided to the trees were taken up in the plant tissues. Lastly, the mineral nutrients could support the post-harvest longevity of fruit. Higher calcium levels, for instance, are widely reported to be associated with lower rind disorders in citrus.

I'm currently reading the literature and trying to gain insight into how these results could be useful to citriculture. Please feel free to contact me for further discussion (or clarity) on the results or for any comments or suggestions. Kind regards, Ida - [email protected]. For product enquiries contact [email protected]

REFERENCES

Mayer AB, Trenchard L, Rayns F. Historical changes in the mineral content of fruit and vegetables in the UK from 1940 to 2019: a concern for human nutrition and agriculture. Int J Food Sci Nutr. 2022 May;73(3):315-326. doi: 10.1080/09637486.2021.1981831. Epub 2021 Oct 15. PMID: 34651542.

McCance, R.A. and Widdowson, E.M., 2000. A study on the mineral depletion of the foods available to us as a nation over the period 1940 to 1991.?Summary of 1st to 5th Edition “The Chemical Composition of Foods”, RSC/MAFF.

Thomas, D., 2007. The mineral depletion of foods available to us as a nation (1940–2002)–a review of the 6th Edition of McCance and Widdowson.?Nutrition and Health,?19(1-2), pp.21-55.

Yeatman, F. and Yeatman, K., 2020. Decline in nutrients in soils and foods, and the role of nutrients.?Adv. Agri. Sci. Oasis Agri (PTY) LTD www. oasis-agri. co. za.