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In‐furrow starter fertilization for corn (Zea mays L.) is being preferred to alternative starter application methods by farmers in the U.S. Corn Belt. This study assessed corn grain yield, early growth (V5 to V6), and early P and K uptake responses to in‐furrow P–K starter fertilization with or without broadcast P–K fertilization for 2‐yr corn–soybean [Glycine Max (L.) Merr.] rotations. Sixteen trials were conducted on Iowa fields managed with no‐till or chisel‐plow tillage. Soil‐test P (STP) was 5 to 77 mg P kg−1 (Bray‐P1), and soil‐test K (STK) was 88 to 237 mg K kg−1 (ammonium acetate). Treatments replicated four times were a control, 3–8–15 (N–P–K) liquid starter at 5 to 7 kg P ha−1 and 10 to 14 kg K ha−1, granulated P–K fertilizer broadcast at 49 to 66 kg P ha−1 and 112 to 140 kg K ha−1, and broadcast plus starter. Nitrogen was applied across all treatments. Fertilization increased grain yield at nine sites (0.80 to 2.11 Mg ha−1). Starter fertilization produced less yield than broadcast fertilization at five sites (0.30 to 1.48 Mg ha−1 less), four of which tested low in STP (≤15 mg P kg−1). Starter fertilization in addition to broadcast fertilization did not increase yield further at any site. Starter fertilization increased corn early growth and P and K uptake more than broadcast fertilization did at most sites. In‐furrow starter P–K fertilization for corn is not an effective practice when applied in addition to 2‐yr broadcast P–K fertilization rates for corn–soybean rotations.

Deep fertilization has been tested widely for nitrogen (N) use efficiency but there is little evidence of its impact on N leaching and the interplay between climate factors and crop N use. In this study, we tested the effect of three fertilizer N placements on leaching, crop growth, and greenhouse gas (GHG) emissions in a lysimeter experiment over three consecutive years with spring-sown cereals (S1, S2, and S3). Leaching was additionally monitored in an 11-month fallow period (F1) preceding S1 and a 15-month fallow period (F2) following S3. In addition to a control with no N fertilizer (Control), 100 kg N ha −1  year −1 of ammonium nitrate was placed at 0.2 m (Deep), 0.07 m (Shallow), or halved between 0.07 m and 0.2 m (Mixed). Deep reduced leachate amount in each cropping period, with significant reductions ( p  < 0.05) in the drought year (S2) and cumulatively for S1-S3. Overall, Deep reduced leaching by 22, 25 and 34% compared to Shallow, Mixed and Control, respectively. Deep and Mixed reduced N leaching across S1-S3 compared with Shallow, but Deep further reduced N loads by 15% compared to Mixed and was significantly lowest ( p  < 0.05) among the fertilized treatments in S1 and S2. In S3, Deep increased grain yields by 28 and 22% compared to Shallow and Mixed, respectively, while nearly doubling the agronomic efficiency of N (AE N ) and the recovery efficiency of N (RE N ). Deep N placement is a promising mitigation practice that should be further investigated.

AIMS: Plant root system architecture adapts to the prevailing soil environment and the distribution of nutrients. Many species respond to localised regions of high nutrient supply, found in the vicinity of fertiliser granules, by elevating branching density in these areas. However, observation of these adaptations is frequently limited to plants cultured in idealised materials (e.g., hydrogels) which have a structure-less, homogenous matrix, which are spatially limited and in the case of rhizotron observation provide only 2D data that are not fully quantitative. METHODS: In this study, in vivo, time resolved, micro-focus X-ray CT imaging (μCT) in 3D was used to visualise, quantify and assess root/fertiliser interactions of wheat plants in an agricultural soil during the entire plant life cycle. Two contrasting fertilisers [Triple superphosphate (TSP) and struvite (Crystal Green®)] were applied according to 3 different treatments, each providing an equivalent of 80 kg P₂O₅ ha⁻¹ (struvite only, TSP only and a 50:50 mixture) to each plant. μCT scans (60 μm spatial resolution) of the plant roots were obtained over 14 weeks. RESULTS: This is the first time that in situ root/soil/fertiliser interactions have been visualised in 3D from plant germination through to maturity. Results show that lateral roots tend to pass within a few millimetres of the phosphorus (P) source. At this length scale, roots are able to access the P diffusing from the granule. CONCLUSIONS: Quantitative analysis of root/fertiliser interactions has shown that rooting density correlates with granule volume-loss for a slow release, struvite fertiliser.

Purpose: Yam cultivation in soils of low fertility has been a major cause of yield decline in Nigeria. The inadequacies associated with either inorganic or organic fertilizer in the aspects of crop growth and productivity necessitated the introduction of organomineral fertilizers. However, information on the appropriate placement method for sustainable cultivation is still limited. Hence, fertilizer type and placement method were evaluated on white yam yield.Method: Dioscorea rotundata (Tdr 219) performance under different fertilizer types [NPK, 15-15-15 and organomineral fertilizer (OMF) at 30 kg N/ha], and different methods of placement (Side/spot and Ring/circular placements) were evaluated.Results: The average tuber length, circumference, number of ware tubers, and yam tuber weights were higher under NPK treatment, while the number of tubers was higher in OMF treatment. All parameters observed were increased by ring fertilizer placement method compared to side placement. The interaction of fertilizer type and method of placement indicated that under OMF, the ring placement produced comparatively higher tuber weight (13390.0 kg/ha) than side placement (13166.6 kg/ha). However under NPK fertilizer, side placements enhanced tuber weight (15173.3 kg/ha) compared with ring placement (15076.6 kg/ha). The residual cropping revealed that the highest and significant tuber weight was observed in OMF fertilizer with ring placement compared to the other treatments.Conclusion: Side placement was appropriate for NPK fertilizer, however, applying organomineral fertilizer at 2000 kg/ha with ring placement was recommended for the cultivation of yam in low fertility soils.

Typical small-pot culture systems are not ideal for controlled environment phenotyping for drought tolerance, especially for root-related traits. We grew soybean plants in a greenhouse in 1-m rooting columns filled with amended field soil to test the effects of drought stress on water use, root growth, shoot growth, and yield components. There were three watering treatments, beginning at first flower: watered daily to 100% of the maximum soil water holding capacity (control), 75% (mild drought stress), or 50% (drought stress). We also tested whether applying fertilizer throughout the 1-m soil depth instead of only in the top 30 cm would modify root distribution by depth in the soil profile and thereby affect responses to drought stress. Distributing the fertilizer over the entire 1-m soil depth altered the root biomass distribution and volumetric soil water content profile at first flower, but these effects did not persist to maturity and thus did not enhance drought tolerance. Compared to the control (100%) watering treatment, the 50% watering treatment significantly reduced seed yield by 40%, pod number by 42%, seeds per pod by 3%, shoot dry matter by 48%, root dry matter by 53%, and water use by 52%. Effects of the 75% watering treatment were intermittent between the 50 and 100%. The 50% treatment significantly increased root-to-shoot dry matter ratio by 23%, harvest index by 17%, and water-use efficiency by 7%. Seed size was not affected by either fertilizer or watering treatments. More than 65% of the total root dry matter was distributed in the upper 20 cm of the profile in all watering treatments. However, the two drought stress treatments, especially the mild drought stress, had a greater proportion of root dry matter located in the deeper soil layers. The overall coefficient of variation for seed yield was low at 5.3%, suggesting good repeatability of the treatments. Drought stress imposed in this culture system affected yield components similarly to what is observed in the field, with pod number being the component most strongly affected. This system should be useful for identifying variation among soybean lines for a wide variety of traits related to drought tolerance.

Improving fertility of marginal soils for the sustainable production of biomass is a strategy for reducing land use conflicts between food and energy crops. Digestates can be used as fertilizer and for soil amelioration. In order to promote plant growth and reduce potential adverse effects on roots because of broadcast digestate fertilization, we propose to apply local digestate depots placed into the rhizosphere. We grew in large mesocosms outdoors for three growing seasons and in rhizotrons in the greenhouse for 3 months both filled with marginal substrate, including multiple sampling dates. We compared digestate broadcast application with digestate depot fertilization and a mineral fertilizer control. We show that depot fertilization promotes a deep reaching root system of seedlings followed by the formation of a dense root cluster around the depot-fertilized zone, resulting in a fivefold increased biomass yield. Temporal adverse effects on root growth were linked to high initial concentrations of ammonium and nitrite in the rhizosphere in either fertilizer application, followed by a high biomass increase after its microbial conversion to nitrate. We conclude that digestate depot fertilization can contribute to an improved cultivation of perennial energy-crops on marginal soils.

Many agricultural soils worldwide in their natural state are deficient in phosphorus (P), and the production of healthy agricultural crops has required the regular addition of P fertilisers. In cropping systems, P accumulates almost predominantly in inorganic forms in soil, associated with aluminium, calcium and iron. In pasture soils, P accumulates in both inorganic and organic forms, but the chemical nature of much organic P is still unresolved. The P use efficiency (PUE) of fertilisers is generally low in the year of application, but residual effectiveness is important, highlighting the importance of soil P testing prior to fertiliser use. With increasing costs of P fertiliser, various technologies have been suggested to improve PUE, but few have provided solid field evidence for efficacy. Fluid fertilisers have been demonstrated under field conditions to increase PUE on highly calcareous soils. Slow release P products have been demonstrated to improve PUE in soils where leaching is important. Modification of soil chemistry around the fertiliser granule or fluid injection point also offers promise for increasing PUE, but is less well validated. Better placement of P, even into subsoils, also offers promise to increase PUE in both cropping and pasture systems.

Deep placement of nitrogen (N) fertilizer has become one of the effective management practices for increasing crop yield and improving N recovery efficiency (NRE). However, it is unclear how different N fertilization depths affect grain yield, nitrogen use efficiency, and root characteristics in direct-seeded rice (DSR) in South China. Here, we conducted stainless steel-box experiment to evaluate the effects of different N fertilization depths at four fertilization depths (0, 4, 8, and 12 cm, written as D0, D4, D8, and D12, respectively) with a conventional ammonium bicarbonate fertilizer (TN = 17.7%) (150 kg N ha−1) and a control (no N fertilizer applied, CK) on grain yield, NRE, and root characteristics of DSR. The results indicated that both D8 and D12 significantly increased grain yields by 72.91 and 81.84%, respectively, compared with CK. The highest nitrogen agronomic efficiency (NAE) and NRE were found under D12 treatment, which were increased by 165.42 and 129.45% compared to D0, respectively. We also found that deep placement of N fertilizer (both D8 and D12) could also promote rice root growth such as larger root length, root superficial area, and thicker root diameter. Furthermore, nitrate reductase (NR), glutamine synthetase (GOGAT), and glutamine synthetase (GS) activities of flag leaves at the heading stage were also increased. The result shows that both 8 and 12 cm are relatively reasonable fertilization depths depended on adopted rice varieties when ammonia bicarbonate fertilizer is used in DSR production.

PurposeExcess anion uptake in the form of nitrate has been shown to reduce soil acidification. The question is to what extent the deep placement of calcium nitrate can increase this root-induced alkalization in reducing subsurface soil acidity.MethodsWheat and canola were grown for 35 days in reconstructed soil columns comprising of topsoil (pHCaCl2 5.4) in 0–10 cm and subsurface soil (pHCaCl2 4.8) in 10–50 cm. Two forms of 15N-enriched fertilizers (urea versus calcium nitrate at 237 mg N per column) with or without P fertilizer (NaH2PO4 at 99 mg P per column) were placed at 0–10, 10–20, or 20–30 cm depth. Root proliferation, rhizosphere pH, and shoot 15N recovery were quantified.ResultsUptake of Ca(NO3)2 increased pH up to 0.5 and 0.2 units in the rhizosphere and bulk soil, respectively, in all treated layers compared to those with urea. The combined application of nitrate and P fertilizer facilitated plant nitrate uptake and hence rhizosphere alkalization. Significant increases up to 10% and 22% in shoot and root biomass, respectively, were observed in the combination of nitrate and P treatments compared with the combined urea and P treatments. The nitrate treatment significantly increased the 15N recovery of fertilizer in both wheat and canola up to 20% compared with the urea treatment.ConclusionsThe increased nitrate uptake reduced subsurface acidity. The combination of nitrate and P treatment can facilitate alkalinity movement downward, hence ameliorating subsurface soil acidity.

Knowledge on growth and nutrient uptake characteristics of urban trees and effective strategies to grow trees can help accomplish the goal of urban afforestation initiatives in a sustainable way. Thus, the study investigated the effects of different vermicompost (VC) application placements on the growth and nutrient uptake of three contrasting tree species (fast-growing Betula platyphylla and Larix kaempferi and slow-growing Chamaecyparis obtusa) to provide implications for growing tree stocks for sustainable urban afforestation programs. Five placement methods were used in the greenhouse trial: no fertilization (CON), surface placement (VCs), subsurface placement at 6-cm depth (VCc), bottom placement (35-cm depth (VCb)), and mixed with soil (VCm). We measured the growth parameters such as height, root collar diameter (RCD), and biomass and analyzed foliar nutrient concentrations in response to different placement treatments of VC. Relative height growth was the highest at VCc (132% (B. platyphylla), 114% (L. kaempferi)) and VCs ((57%) C. obtusa). Significant improvement in aboveground and belowground biomass growth of all species at VCs and VCc compared to the other treatments was also observed. Generally, VC treatments significantly increased N concentration compared to CON in all species. In conclusion, fertilizing the fast- and slow-growing urban tree species using VCs and/or VCc is relevant to growing high quality planting stocks for sustainable urban afforestation purposes.