How to produce more, with less inputs, and more gently on the environment?

Those phrases pretty much sum up the current main driver of agricultural change worldwide and the research question behind another recent trial that we are happy to share.

Seeking sustainability

For a century or more, we can all recognize that the push was for productivity, perhaps at all costs. Now, we all know farming businesses that want to lower their input use, increase efficiency, and lessen their negative environmental effect. The question is how? Research with Polysulphate in France may be helping to answer that question.

Alfalfa field in Reims, France

Alfalfa trial results

Alfalfa is a significant livestock forage crop. The French research team wanted to examine the response of rainfed alfalfa yield and quality to increasing proportions of the natural polyhalite mineral that comprises Polysulphate, and to estimate the crop’s carbon footprint, compared to KCl alone and to an unfertilized control.

The trial, funded by the International Potash Institute (IPI), consisted of 3 replications on a randomized complete block design. Four different treatments were established with combinations of 2 different sources of potassium, potassium chloride (KCl), and Polysulphate at a similar dose of K (300 kg K₂O ha^-1) at 4 different proportions: all K from KCl, and 10%, 20 and 40% of the K from Polysulphate. A control was established which received no additional nutrient supply.

The trial was established on an alfalfa field on its 2^nd year of cultivation, on a silt-loam calcareous soil (pH 8.2) at Vésigneul-sur-Marne, France. Yield and feed quality parameters were measured in 6 cuts during 2019 and 2020.

In short, the results show that more balanced or optimized nutrition provision with Polysulphate was beneficial to both crop productivity and feed value and to its overall carbon footprint

Better balanced nutrition brings better news

The research report summarizes that, over the two-year experiment period, the treatments with Polysulphate yielded 1.6 ton ha^‑1 more than crop applied only with KCl, and 3.1 ton ha^‑1 more than the K₀ control, differences that were particularly pronounced in the second, drier, 2020 season.

A clear trend was observed in all cuts – especially in the second year – with improvements in all the quality parameters of the alfalfa fertilized with Polysulphate (protein contents).

An assessment of the C footprint of each treatment was obtained with the Cool Farm Tool, to assess the environmental impact of each strategy. Carbon footprints, calculated as CO₂ emissions on the basis of dry matter production, were slightly lower in the Polysulphate-applied crop. These are all positive indications of the benefits of optimized crop nutrition and signpost areas for future research work.

Effects of the fertilizer treatments on the alfalfa cumulative yield over the two successive growing seasons, 2019 and 2020. Similar letters indicate no statistical differences between treatments at P>0.05. Lines above bars represent standard deviations.

Browse sources of inspiration

Whether or not alfalfa is a crop that you are connected with, the themes behind the research questions for this recent research in the fodder fields of France are common to all of us. Browsing the outcomes of scientific work like this is an important part of getting a balanced diet of information, in order to help farming businesses refine, re-focus and refresh their crop nutrition strategy.

So, finally – if we can use just one more feed-related phrase, we hope that this edition of the Polysulphate Missive gives you food for thought.