Recovery of fertilizer N by three successive corn (Zea mays L.) crops and as inorganic N in the soil profile following the last crop ranged from 72 to 88%. Total amount of NO3‐N in the soil profiles was directly related to the rate of N application and to the frequency of corn in the rotation. More leaching of NO3‐N generally occurred between fall and spring samplings than during the growing season. The most effective methods indicated for limiting the amounts of NO3‐N passing through the soil profile to the water table include: limiting rates of N fertilizer to approximately that required by the crop, reducing the acreage and frequency of corn or other crops that received fertilizer N in the rotation, and maintaining a crop cover on the land as much of the time as is feasible.

Hydrogels are soft, water-based gels with widespread applications in personal care products, medicine and biomedical engineering. Many applications require structuring the hydrogel into complex threedimensional (3D) shapes. For these applications, light-based 3D printing methods offer exquisite control over material structure. However, the use of these methods for structuring hydrogels is underdeveloped. In particular, the ability to print hydrogel objects containing internal voids and channels is limited by the lack of well-characterized formulations that strongly attenuate light and the lack of a theoretical framework for predicting and mitigating channel occlusion. Here we present a combined experimental and theoretical approach for creating well-defined channels with any orientation in hydrogels using light-based 3D printing. This is achieved by the incorporation of photoblocker and the optimization of print conditions to ensure layer-layer adhesion while minimizing channel occlusion. To demonstrate the value of this approach we print hydrogels containing individual spiral channels with centimeter-scale length and submillimeter-scale crosssection. While the channels presented here are relatively simple, this same approach could be used to achieve more complex channel designs mimicking, for example, the complex vasculature of living organisms. The low cytotoxicity of the gel makes the formulation a promising candidate for biological applications.

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Studies were carried out in the greenhouse and field to elaborate the mechanism of P‐Zn interaction in the nutrition of corn (Zea mays L.). From this work depressive action of P on Zn uptake of corn appears to be largely physiological in nature, expressed at root surfaces and/or in root cells, and is not chemical inactivation of Zn by P in soil. Translocation of Zn from roots to tops is inhibited by elevated P concentration, with resulting sharp reduction in Zn concentration of nodal and internodal tissues. No clearly definable P/Zn ratio in tissue was found above which yield restriction could be predicted. Corn seems to tolerate high concentrations of P in its tissues provided some modest quantity of Zn is present. Other elements counteract somewhat the damaging effects of P. Concurrently placed N promotes Zn uptake at the same time that it benefits P utilization. Increased level of native or applied K reduces the depressive effects of P on Zn.

No abstract