Residual effects of B and Zn fertilizers applied to dry season crops on the performance of the follow‐up crop of maize in Nepal

Abstract

AbstractBackground: Diversified food crop production systems with high‐value vegetable crops are increasingly replacing conventional rice–wheat rotations across Nepal. These newly emerging systems are likely to enhance the demand for the micro‐nutrients boron (B) and zinc (Zn), which are already widely deficient throughout in Nepal. However, B and Zn fertilizers often are either unavailable in rural areas, not available in a timely manner, or when available not affordable by smallholder farmers.Aims: To overcome multiple constraints concerning the need and efficient use of B and Zn amendments in a technical feasible way with a high financial efficiency for farmers and without compromising the environment, the current study assessed whether soil stock provisioning, e.g., B and Zn fertilizer applications to dry season crops, may provide sufficient residual effects for the succeeding non‐fertilized wet season crop.Methods: A pot experiment was conducted in a sheltered greenhouse using two contrasting but representative soil types (Acrisol and Fluvisol) collected from rice‐ and from maize‐based production systems in Nepal. Boron and Zn amounts were supplied individually or in combination to wheat, cauliflower, and tomato grown in the dry season of 2018, whilst measuring biomass accumulation, B and Zn concentrations in plant tissues of all crops which allowed calculating B and Zn uptake in the unfertilized follow‐up crop of maize.Results: Soil‐applied B and Zn fertilizers, sole and combined, slightly enhanced biomass of the succeeding non‐fertilized maize only, but significantly increased total B and Zn plant uptake, with significant differences between soil types. Furthermore, while maize shoot B concentrations were consistently increased above the critical levels in both soils, but especially in the Fluvisol after wheat and cauliflower pre‐crops, Zn uptake of maize was more enhanced in the Acrisol.Conclusions: The residual effects of B and/or Zn applied to preceding dry season crops benefitted the subsequent wet season maize, especially after the pre‐crops wheat and cauliflower in the Fluvisol for B, and after wheat and tomato in the Acrisol for Zn. They may suffice to attain reasonable yields of wet season crops in the emerging vegetable‐based cropping systems of Nepal, even if fertilizers are not consistently available. The magnitude of the residual effects of pre‐applied Zn largely depended on the soil type, while those of B were mainly determined by the pre‐crop.