Yield and nitrogen balance in corn grown under no-tillage system

ABSTRACT The corn crop is highly responsive to nitrogen fertilization; however, the application of high doses generally causes a reduction in the use efficiency of fertilizer. In this sense, this study aimed to determine the yield and nitrogen balance in corn grown under the no-tillage system. The experiment consisted of the application of four nitrogen doses (0, 30; 70 and 95 kg ha-1). In all plots with the AG 1051 hybrid corn, 80 and 56 kg ha-1 of P2O5 and K2O were applied, respectively. The experiment was arranged in a randomized block design with five replications. The grain yield had a linear increasing behavior according to the nitrogen doses, which reached 5,684.79 kg ha-1. The fertilization efficiency and the N extraction increased linearly with the increase of the nitrogen doses, obtaining with the highest dose the extraction of 114.93 kg ha-1 of N and a fertilization efficiency of 65%. The soil N stock of 4,489 kg ha-1 provides corn plants with 52.81 kg ha-1 of this nutrient. Corn adjusts the biomass production according to the availability of nitrogen, with no effect of N doses on the nutrient content in plant tissues.

Tracking fertiliser and soil nitrogen in irrigated cotton: uptake, losses and the soil N stock

This paper explores the importance of the N loss pathways relative to the immobilisation and soil mineral N supply during a cotton season. Despite using an agronomic practice of splitting urea application to reduce losses and an optimal rate (232kg urea-N ha–1) for the experiment, the average fertiliser recovery was 32%, which indicates that soil N mineralisation is a key source of N for irrigated cotton production systems. A large amount of the fertiliser (62kgNha–1) was immobilised in the soil at the end of the season and during the season the soil supplied 159kgNha–1 to the plant via mineralisation. During the season, large N losses occurred from the field via the atmospheric, deep drainage and surface run-off pathways (143kgNha–1). The losses occurred directly after fertilisation, predominantly at the start of the season when the majority of the urea fertiliser was applied (180kg urea-N ha–1). This indicates that the form, placement and timing of the fertiliser did not synchronise with soil and crop N dynamics and irrigation practice. Over the course of the measurement season, based on the N inputs, losses and storage budget, a 42kgNha–1 soil deficit was observed. Further longer term work is required to quantify the magnitude and significance of the soil N stock across different systems.

Changes in Regulating Ecosystem Services following Establishing Exclosures on Communal Grazing Lands in Ethiopia: A Synthesis

In four separate studies undertaken in the northern highlands of Ethiopia, changes in regulating ecosystem services, economic viability, and the perception of local communities following establishing exclosures on communal grazing lands were investigated. Replicated 5-, 10-, 15-, and 20-year-old exclosures were selected and paired each exclosure with an adjacent grazing land. All exclosures displayed higher ecosystem services than communal grazing lands. Differences between exclosures and grazing lands varied between 29 (±4.9) and 61 (±6.7) Mg C ha−1 for ecosystem carbon stock (ECS), 2.4 (±0.6) and 6.9 (±1.8) Mg ha−1 for total soil N stock, and 17 (±3) to 39 (±7) Kg ha−1 for the available P stock, and all differences increased with exclosure duration. Differences in plant species richness and biomass between an exclosure age and communal grazing land were higher in oldest than in youngest exclosures. Over a period of 30 years, sequestered carbon dioxide was 246 Mg ha−1, total soil nitrogen increased by 7.9 Mg ha−1, and additional available phosphorous stocks amounted to 40 kg ha−1. The Net Present Value of exclosures ecosystem services under consideration was about 28% (837 US$) higher than alternative wheat production indicating that exclosures are competitive to alternative land uses. There are substantial opportunities to mobilize the local communities in efforts to establish exclosures, given that more than 75% had a positive view on exclosures effectiveness to restore degraded ecosystems. Establishing exclosures on communal grazing lands can be effective for restoring degraded ecosystems and the services that they provide.