Are catchment-scale nitrogen and phosphorous use efficiencies controlled by climate?

<p>Nutrient loss from agricultural fields imparts increased fertilizer costs as well as negative consequences for the natural environment. Given that water availability mediates both nutrient uptake by plants as well as nutrient leaching, we hypothesize that hydrologic conditions can explain variations in nutrient use efficiencies, defined as ratios of the nutrient amounts in harvested yield and in inputs. We analyze data from 110 US catchments with agricultural area comprising more than 10% of the watershed and compute nitrogen and phosphorus use efficiencies (NUE and PUE) over the period 1988-2007. To assess if NUE and PUE are related to hydrologic conditions, we consider the evaporative ratio ET/P (calculated as evapotranspiration divided by precipitation) as a predictor in a linear mixed effect model. We test the hypotheses that the nutrient use efficiencies increase with ET/P, through increased water and nutrient retention, and that the nutrient efficiencies increase through time. We found that both nutrient use efficiencies increased through time: NUE increased in the period analyzed in 88% of catchments, while PUE in 90% of catchments. Both NUE and PUE were largely driven by significant increases in N and P amounts in yield. The evaporative ratio was positively related to NUE. Moreover, we found an interaction between ET/P and time, such that the ET/P effect on NUE decreased in the period 1998–2007. The evaporative ratio was also positively related to PUE. Other potential drivers were assessed, including interaction between ET/P and time, as well as the percentage of agricultural area in each catchment. Our results show that changes in climate that include increased evaporation and decreased precipitation can lead to increase N use efficiencies without decreasing yields. The implications of our findings in terms of the release of N and P to water bodies has particular relevance in terms of climate change, as higher temperatures and lower precipitation (i.e. increasing evaporative ratios) will potentially lead to increased nutrient retention and therefore decreased nutrient leaching from agricultural fields.</p>

Comparative Behavior of Dracaena marginata Plants Integrated into a Cascade Cropping System with the Addition of Hydrogen Peroxide

The reuse of crop drainage into other crops, in the form of a cascade cropping system, is a feasible environmental solution where high inputs of water and fertilizer are used for crop growth and lower efficiency rates, associated with a high discharge of water and fertilizers into the environment, are present. Dracaena marginata plants were cultured in containers with sphagnum peat moss and were subjected to three different fertigation treatments for eight weeks: Dm0 (standard nutrient solution or control treatment), Dm1 (raw leachates), and Dm2 (raw leachates with additional H2O2), where the leachates were collected from a Chrysalidocarpus lutescens-Dracaena deremensis cascade cropping system. At the end of the harvesting, growth parameters, pigment concentration, leaf and root proline, total soluble sugar concentrations, and water and nutrient use efficiencies were assessed for each fertigation treatment. Plant height, root, stem, and total dry weight increased under fertigation with leachates with H2O2. The fertigation with leachates with or without H2O2 increased the red index value. There were no clear trends between the fertigation treatments with regards to pigment concentrations and biochemical parameters (proline and total soluble sugar concentrations). The addition of H2O2 to the leachate increased N concentration in the organs assessed, as well as the water and nutrient use efficiencies. There were no variations in H2PO4−, SO42−, Na+, and Mg2+ concentration in the chemical composition of the substrate between fertigation treatments. The positive results reported in this experiment suggest the potential growth of Dracaena marginata with leachate and hydrogen peroxide in a cascade cropping system.

Sorption of urea hydrogen peroxide by co-pyrolysed bone meal and cow dung slowed-down phosphorus and nitrogen releases but boosted agronomic efficiency

Co-pyrolysis of animal manure biomass with bone meal (BM) and soaking of the resultant biochar in urea containing solutions may offer a sustainable and cheap way of formulating slow-release nitrogen (N) and phosphorus (P) fertilisers. This method can lead to optimisation of the carbon sequestration capacity of the biochar, abatement of environmental pollution by P and N and alleviation of the severity of the projected future scarcity of P. A few studies have indicated that sorption can create efficient slow-release fertilisers although all of them utilised charged moieties such as ammonium ions to formulate them and as a result, there is a paucity of data concerning the efficiency of fertilisers formulated using uncharged compounds like urea. It’s against that background that we examined the possibility of leveraging co-pyrolysis and sorption with urea containing solutions to formulate slow-release N and P fertilisers along with assessing the agronomic efficiency of the formulated fertilisers through cultivating lettuce in pots for two seasons. Both urea-hydrogen peroxide (UHP) and urea were utilised as N sources. UHP (CDBM-UHP) and urea (CDBM-Urea) containing biochars averagely released 64.40% and 87.00% of the added N, respectively over the 28-day incubation period with the amount of N released decreasing with increasing concentrations of BM in the biochar. Lettuce yields and nutrient use efficiencies of N and P were higher in the CDBM-UHP than in the CDBM-Urea treatments. It’s therefore clear that sorption of UHP by BM containing biochar concomitantly slows-down releases of N and P and boosts the agronomic efficiency of the fertilisers.

Economic Performance and Nutrient Use Efficiency of Onion (Allium Cepa L.) Under N, K and S Nutrient Combinations in Northern Ethiopia

Background: Nitrogen (N), potassium (K) and sulfur (S) nutrient elements play an important role in the growth and bulb yield of onion. However, imbalanced nutrient application leads onion producers to get lower onion bulb yield. Hence, the supply of adequate and balanced plant nutrients is important in order to achieve better nutrient utilization as well as proper growth and high yield. Objective: To evaluate the agronomic and economic performance as well as nutrient efficiency of onion in response to the combined application of nitrogen, potassium and sulfur nutrient levels. Method: The field experiment was conducted during 2016/17 to test agronomic, economic and nutrient use efficiency of eighteen treatment groups with the combination of three levels of N, three levels of K and two levels of S nutrient on onion using a randomized complete block design. Results: The combined application of N, K and S nutrient levels appreciably resulted in significant variation not only on growth and bulb yield of onion but also on the economic performance and nutrient use efficiencies. Increased growth and improved bulb yield of onion as well as better nutrient uptakes and recoveries were observed in plots treated with relatively higher NKS rates. However, enhanced Agronomic Efficiency (AE) and Partial Factor Productivity (PFP) were obtained from plots treated with no N and K nutrient applications. Conclusion: Higher growth, improved bulb yield and enhanced nutrient use efficiencies (nutrient concentrations, uptakes and recoveries) were obtained from onion plants cultivated using a relatively higher NKS nutrient level. However, from the economic point of view, onion production using combined application of 69 kg N ha-1 and 15 kg S ha-1 was the most profitable, irrespective of the K level.