The nitrogen fertilizer conundrum: why is yield a poor determinant of crops’ nitrogen fertilizer requirements?

Sustainable agriculture requires optimizing nitrogen fertilizer applications to crops. It is commonly assumed that higher yielding crops need more nitrogen, and smaller less, despite some evidence that optimum nitrogen applications are poorly related to yields. In contrasting experiments, we show that year-to-year climatic variations cause the poor correlations. New approaches to nitrogen recommendations are needed to account for this uncertainty.

Thorburn, P.J., Biggs, J.S., Puntel, L.A. et al. The nitrogen fertilizer conundrum: why is yield a poor determinant of crops’ nitrogen fertilizer requirements?. Agron. Sustain. Dev. 44, 18 (2024).

Insect excrement as an alternative fertilizer for sustainable agriculture

Picture by Dennis Kress

The mass breeding of insects for animal protein production could compete efficiently with conventional livestock to feed the ever-growing human population. Insect excrement (frass) is one of the main outputs of this process. In a recent review, scientist Poveda highlighted the benefits of reusing frass as bio-fertilizer in agriculture. Insect frass provides soils with nutrients, beneficial microorganisms and different biomolecules of great interest. Therefore it promotes plant growth and increases crop productivity for a sustainable agriculture.

Phosphorus fertilization reduces zinc concentration of cereals

Picture copyright Zhang et al.

Zhang et al. highlighted recently that phosphorus fertilizer application reduces grain Zinc (Zn) concentration by 16.6% for wheat and 20.2% for maize. However, Zn content in grain of wheat and rice increases with increasing P fertilization. They ascribe this effect to a mere ‘dilution effect’ (i.e., same abundance in greater biomass) because grain biomass increases in response to P applications while root Zn uptake efficiency declines. They reckoned that attempts for increasing grain Zn concentration by biofortification should consider these effects carefully.

Novel insights in cassava NPK nutrition

Picture copyright Adiele et al.

Fertilizing cassava improves productivity and fulfills the rising demand for food, feed or raw materials in processing industries. For cassava field crops, Scientists Adiele et al. determined crop growth dynamics, NPK demand, and nutrient allocation to organs. They developed nutrition indices for N, P and K using a “dilution curve” approach. Their novel insights help to identify sustainable management practices to optimize fertilizer application, develop nutrient-limited crop models and improve cassava production.

Do all grain legumes provide comparable ecosystem services?

Picture copyright Guinet et al.

Legumes have a key role to play in agriculture transition towards greater sustainability, due to their ability to provide ecosystem services. However, choosing the right grain legumes to provide specific ecosystem services remains difficult because references are lacking for a diversity of species. Guinet et al. characterized and distinguished ten-grain legumes according to their ability to deliver contrasted nitrogen-related ecosystem services. Their study provides a rationale for choosing legumes species according to intended objectives and for adjusting N management in cropping systems.

Optimizing nitrogen fertilization for sustainable potato production

Picture copyright Wang et al.

Food security and environmental protection require optimizing crop N fertilization. Scientists Wang et al. reviewed studies on Chinese potato production to determine the optimal N-fertilization rate at a regional scale. The recommended rate improved N use efficiency and agronomic efficiency without sacrificing potato yield. These practices establish a reasonable trade-off between potato production and N-fertilizer management for the development of more sustainable agricultural systems.

Cover crops with subterranean clover reduce the adoption of synthetic herbicides and fertilizers

Picture copyright Scavo et al.

Cover crops are gaining in popularity for their positive effects in agroecosystems, especially under organic farming and in low-input agriculture. Based on a 3-year field experiment, scientists Scavo et al. found that self-residing subterranean clover with the incorporation of dead mulches into the soil reduced weeds and increased the soil nitrogen. These results are useful for reducing the utilization of synthetic herbicides and mineral nitrogen fertilizers in Méditerranéenne orchards.

Intercropping grain legumes with cereals reduces synthetic fertilizer requirement

Picture copyright ES Jensen

Intercropping or cultivating simultaneously more than one species on the same land is a means of improving resource use in agriculture. In a recent analysis, scientists Jensen et al. revealed that intercropping grain legumes with cereals could reduce the requirement for synthetic N-fertilizer by 26% on a global scale, thus allowing important net land saving. Intercropping supports, therefore, the development of more sustainable cropping systems.

Increasing soil carbon storage in agroecosystems under low nutrient inputs

Picture copyright Frak Elzbieta, Inra

Agriculture has to reduce synthetic inputs. Consequently, ecological processes and alternative agricultural practices will become the main regulators of carbon (C), nitrogen (N) and phosphorus (P) in cropped soils. Scientists Bertrand et al. recently observed that soil C storage is constrained by N and P supplies in various agricultural situations. Several agroecological practices that improve nutrient recycling can resolve this constraint.

Cash for trash: recycling urban organic wastes as fertilizers

Picture copyright Thuriès et al.

In sub-Saharan Africa, rapid-growing cities generate increasing volumes of organic wastes that can be recycled and transformed into organic fertilizers. Scientists Thuriès et al. found considerable variability and discrepancy in both agronomic and economic values of these wastes. Their results suggest that the composting process needs to be improved. They reckoned that the humus potential should be calculated to assess more accurately the amendment value and used to adjust their market price.