Dr FG Adriaanse, for Kimleigh Chemicals SA (Pty) Ltd
Along with specific pre-season soil analyses, foliar analyses should be used for diagnosing and treating nutrient deficiencies during seasons. Reasons for performing foliar analyses include leaching of nitrogen (N), boron (B) and molybdenum (Mo) down the soil profile, phosphorus (P) sorption by clay minerals, unavailability of Mo under acidic soil conditions, unavailability of zinc (Zn), B, manganese (Mn), Mo, iron (Fe) under alkaline conditions, and copper (Cu) fixation by organic material.
The norms for dried leaf analysis have been well-established for many crops over the years. Leaf sap analysis was introduced more recently but norms have also been well established for many different crops. Leaf sap analyses include more and different analyses of both older and younger leaves at specific growth stages.
The objectives of this study were to compare the accuracy of diagnosing nutrient deficiencies according to dried leaf analyses and leaf sap analyses, based on soya yield responses to foliar application of new-generation, highly advanced foliar fertilisers from Kimleigh Chemicals SA.
Materials and methods
Leaf samples were taken from a field close to the Vaal River, approximately 30km from Potchefstroom on 4 January 2023. Dried leaf samples were analysed by NviroTek Laboratories and leaf sap by NovaCropControl, and interpreted by Agropedo. According to the dried leaf analyses, deficiencies of B, Cu and Mo were identified whereas the leaf sap analyses indicated Zn, B, Mn, Mo, Fe, P and calcium (Ca) deficiencies.
Soil analyses from October 2021 in respect of the top 15cm increment, showed: clay = 15%; pH (potassium chloride or KCl) = 4,9; P (Bray 1) = 21mg/kg; potassium (K) (AmAc) = 148mg/kg; Ca (AmAc) = 280mg/kg; Mg (AmAc) = 85mg/kg; and S (AmAc) = 6mg/kg. Only 4,3 ton of compost/ha was broadcast, and soil incorporated before planting, but no fertiliser was applied.
Eight foliar spray treatments and four replications were arranged in a randomised block design. This article only focusses on a control treatment which received no foliar spray, a treatment according to deficiencies identified by dried leaf analyses (Treatment 1), and another according to leaf sap analyses (Treatment 2).
Treatment 1 received 48g B/ha, 48g Cu/ha, and 18g Mo/ha. Treatment 2 received 129g Zn/ha, 48g B/ha, 99g Mn/ha, 33g Fe/ha, 18g Mo/ha, 270 g P/ha, and 80 g Ca/ha. Treatment 2 was repeated twice within each replication.
The Metalin range of micronutrients supplied as suspension concentrates from Kimleigh Chemicals were used. Of these elements, Zn, Cu, Mn, and Fe were based on nanotechnology. The watersoluble product, Fertilin CaP from Kimleigh Chemicals, supplied macronutrients. The trial was planted on 15 November 2022 at a plant population of 223 498/ha and treatments were sprayed on 21 February 2023 (R5 growth stage). Harvesting took place on 2 May 2022. Yields were corrected to 12,5% moisture.
Results and discussion
Treatment 1 increased yield by 0,14t/ha (3,88%) above the control, which was statistically significant at 90% (Figure 1). The increase in income at a soya price of R8 500/t is R1 190/ha and the product cost is R209,31/ha resulting in an increase in profit of R980,69/ha. Treatment 2 increased yield by 0,22t/ha (6,09%) above the control, which was statistically significant at 95%. The increase in income is R1 870/ha and the product cost is R521,50/ha resulting in an increase in profit of R1 348,5/ha.
The accuracy of results is further confirmed by a very low coefficient of variation (CV) for yield of 2,72%.
Conclusions
Soya bean yield responses to foliar applications based on leave sap analyses were economically more justifiable than when based on dried leaf analyses and should therefore be preferred. Leaf sap analyses also identified deficiencies for more elements compared to dried leaf analyses.
The Kimleigh Metalin range of advanced micronutrients together with Ferilin CaP demonstrated to be very effective in addressing nutrient deficiencies. A specific combination of Zn, B, Mn, Mo, Fe, P and Ca increased soya yield which was 95% statistically reliable and economically justifiable, increasing profit above product cost by R1 348,5/ha at a soya price of R8 500/t.
Thanks to Dewald Bothma and Anievaal Boerdery for conducting this trial and providing results. Consult Kimleigh Chemicals for product details, location-specific applications, and references. Visit www.kimleigh.com or call 018 293 1028.