Reduced Fertilizer Inputs Research Articles

Risk efficiency of irrigation to cereals in northeast Germany with respect to nitrogen fertilizer

The potential role of irrigation of cereals as a response to climate change is under debate. Especially under temperate continental conditions empirical evidence of crop yield response to irrigation in interaction with nitrogen fertilizer supply is rare. Besides mean yield effects, irrigation reduces yield variance, which may be an incentive for farmers to use irrigation. This paper investigates the risk-efficiency of irrigation in cereal production in a temperate continental climate, based on data from a long term field experiment on a sandy soil. Irrigation and no irrigation of winter rye (Secale cereale) and winter barley (Hordeum vulgare) were investigated in three different nitrogen (N) fertilizer levels. Crop yield response data (1995–2010) to irrigation and N fertilizer were used to calculate net returns, certainty equivalents (CE) for different levels of risk aversion and the conditional value at risk (CVaR) as a downside risk indicator in two price scenarios. The scenarios were calculated with a total cost and a partial budget approach. Irrigation was found to be profit-maximizing in all partial budget calculations, which sometimes required higher N input to be profit-maximizing. Irrigation and N fertilizer reduction were identified as risk mitigation strategies, even though their impact was limited. Irrigation reduced the downside risk only in the partial budget calculations. The analysis based on the CE did not show improved risk efficiency with irrigated management options. In contrast, reduced fertilizer input proved to be risk efficient at specific levels of risk aversion. The price expectations of winter rye and winter barley had a much higher impact on the ranking of the management options than risk aversion based on the crop yield variances. At low crop prices for all levels of risk aversion, irrigation of winter barley and winter rye was only economically justified if fixed costs for irrigation were not taken into account. At high crop prices, irrigation of winter barley was also justified based on the total cost calculation. However, this advantage was only given at a very low level of risk aversion. With increasing levels of risk aversion irrigation was not efficient based on the CE in the total cost accounting scenario. In conclusion, irrigation of cereals can contribute to downside risk mitigation and increased profits, if fixed costs for irrigation are covered. However, this conclusion holds only when irrigation is combined with an increased N intensity. If total costs need to be accounted for, irrigation in cereals is not an appropriate risk reduction strategy and a reduction of N input is more effective.

Soy-composite Biocontainers Allow for Reduced Fertilizer Inputs during Container-crop Production

Bioplastics and bioplastic composites are a group of emerging sustainable materials that exhibit favorable characteristics for use in horticulture-production containers. Biocontainers made from composite materials of soy [Glycine max (L.) Merr.] bioplastic and poly(lactic) acid (PLA) have been shown to release nitrogen (N) at a rate suitable for supporting plant growth. We hypothesized that fertilizer applications can be reduced while maintaining adequate nutrition levels for plant production when using soy-based containers. To test this hypothesis and quantify potential reduction of fertilizer, we grew marigold ‘Honeycomb’ (Tagetes patula L.) in five prototypes of soy-composite biocontainers [soy bioplastic compounded with PLA or polyhydroxyalkanoates (PHA)] and a petroleum-plastic (polypropylene) control container with five fertilizer treatments supplying 1) 60N‒4P‒49K; 2) 75N‒5P‒61K; 3) 105N‒7P‒85K; 4) 150N‒10P‒122K; or 5) 300N‒20P‒244K mg. At harvest, plants grown in all soy‒PLA composite biocontainers and protein + PLA biocontainers had higher concentrations and contents of N and P compared with plants grown in petroleum-plastic containers across all fertilizer treatments. Shoot K concentrations were highest for plants grown in all soy‒PLA and soy‒PHA biocontainers compared with plants grown in petroleum-plastic containers across all fertilizer treatments, whereas shoot K concentrations in plants grown in protein + PLA biocontainers were equal to or lower than plants in petroleum-plastic containers. Total plant dry weight was greater for plants grown in biocontainers made of 50% soy‒50% PLA and protein + PLA than for plants grown in control containers across all fertilizer treatments except at the highest rate of fertilizer in which plants received 300N‒20P‒244K mg. Our results support the hypothesis that fertilizer inputs can be reduced when using soy-composite biocontainers. Biocontainers made with equal parts soy bioplastic and PLA showed strong potential for achieving adequate plant growth with reduced fertilizer input. Our results demonstrate that fertilizer can be reduced by as much as 80% when growing marigold in containers made of 50% soy‒50% PLA for 6 weeks.

Improving resource-use-efficiency with no-till and crop diversity

AbstractRecently, we conducted a case study that showed a no-till, diverse cropping system increasing corn yields in a semiarid climate compared with a tilled, corn–soybean rotation. Further analysis showed that the no-till system improved resource-use-efficiency of corn; inputs were reduced 42% averaged across five resources. The largest reduction with inputs involved nitrogen fertilizer and fuel. Reduced fertilizer input was attributed to greater soil microbial activity. A surprising trend was that cost of weed management in corn was 45% lower in the no-till system, due to resistant weeds being present only in the tilled, corn–soybean system. Crop diversity in the no-till system suppressed development of weed resistance. Integrating a diversity of crops with no-till can improve efficient use of resources.

Can above‐ground ecosystem services compensate for reduced fertilizer input and soil organic matter in annual crops?

Summary Above‐ground and below‐ground environmental conditions influence crop yield by pollination, pest pressure and resource supply. However, little is known about how interactions between these factors contribute to yield. Here, we used oilseed rape Brassica napus to test their effects on crop yield. We exposed potted plants to all combinations of high and low levels of soil organic matter (SOM) and fertilizer supply, and placed all treatments at a variety of field sites representing a gradient in pollinator visitation rate and pest exposure. We determined the relative contribution of pollinators and pests, SOM and fertilizer supply to yield. We also tested whether SOM can moderate effects of fertilizer on yield and whether soil conditions influence the relationship between above‐ground conditions and yield. Increases in pollinator visitation rate and decreases in pest pressure enhanced yield more than increase in fertilizer supply. Although higher SOM content resulted in plants with more biomass and flowers, under our experimental conditions SOM neither enhanced yield, nor influenced effects of fertilizer, pollinators or pests on yield. The relationships between yield, pollinator visitation rate and pest pressure did not depend on the level of fertilization, suggesting that the effects of fertilizer application and above‐ground (dis)services on yield were additive. In contrast, pollinator visitation rate was more strongly related to yield at low pest pressure than at high pest pressure indicating trade‐offs between above‐ground services and disservices. Synthesis and applications. Our results show that it is possible to increase oilseed rape yield by enhancing pollination, irrespective of supplying mineral fertilizer. Moreover, the fact that below‐ground conditions did not alter the effect of above‐ground conditions suggests that farmers may obtain even higher yields by maximizing both above‐ground ecosystem services and external inputs. Further studies are needed to understand at which point the positive relationships between pollinator visitation and yield, as well as between fertilizer and yield, will level off. Considering above‐ground and below‐ground services and inputs in agro‐ecosystems in conjunction is crucial in order to optimize external inputs for crop yield from an economic and ecological perspective.

A Case Study of Environmental Benefits of Sensor-Based Nitrogen Application in Corn.

Crop canopy reflectance sensors make it possible to estimate crop N demand and apply appropriate N fertilizer rates at different locations in a field, reducing fertilizer input and associated environmental impacts while maintaining crop yield. Environmental benefits, however, have not been quantified previously. The objective of this study was to estimate the environmental impact of sensor-based N fertilization of corn using model-based environmental Life Cycle Assessment. Nitrogen rate and corn grain yield were measured during a sensor-based, variable N-rate experiment in Lincoln County, MO. Spatially explicit soil properties were derived using a predictive modeling technique based on in-field soil sampling. Soil NO emissions, volatilized NH loss, and soil NO leaching were predicted at 60 discrete field locations using the DeNitrification-DeComposition (DNDC) model. Life cycle cumulative energy consumption, global warming potential (GWP), acidification potential, and eutrophication potential were estimated using model predictions, experimental data, and life cycle data. In this experiment, variable-rate N management reduced total N fertilizer use by 11% without decreasing grain yield. Precision application of N is predicted to have reduced soil NO emissions by 10%, volatilized NH loss by 23%, and NO leaching by 16%, which in turn reduced life cycle nonrenewable energy consumption, GWP, acidification potential, and eutrophication potential by 7, 10, 22, and 16%, respectively. Although mean N losses were reduced, the variations in N losses were increased compared with conventional, uniform N application. Crop canopy sensor-based, variable-rate N fertilization was predicted to increase corn grain N use efficiency while simultaneously reducing total life-cycle energy use, GWP, acidification, and eutrophication.

English

Scientific information concerning spatial variability and distribution of soil properties is critical for farmers attempting to increase fertilization efficiency and crop productivity; fertilization based on maps with recommendations related to soil fertility may lead to reduced fertilizer inputs without reducing yield. In the present study, GPS based one hundred fifty surface soil samples (0-15 cm) were collected from dominant cropping system. After processing, the soil samples were analyzed for different soil characteristics in laboratory using standard procedures. The data obtain from laboratory analysis was statistically and geo-statistical interpreted. The results revealed that the 23.6, 28.30, 48.6, 13.9, 25.5 and 54.7% soil samples were found to be deficient in OC, N, P, K, S and Zn, respectively. None of the soil samples were tested low in Cu, Fe, Mn and B. Exponential model was found as the best fit for considered soil parameters whereas, spherical model was found as the best fit for Mn. The best model was used to generate the spatial distribution maps. Spatial maps showed that the soil pH, EC, organic carbon, available N, P, K, S, Zn, Cu, Fe, Mn and B spatially varied and N, P, K, S and Zn were deficient in major areas. Therefore these maps are more useful for guiding site-specific field management for agricultural production and environmental protection. In addition, reduce the losses of nutrients and could be save time and money for fertilizers.   Key words: Geo-statistical, soil types, land use, semi-variogram, kriging, nutrient status.

Radish Planting Date and Nitrogen Rate for Cover Crop Production and the Impact on Corn Yields in Upstate Missouri

Cover crops can increase yield of a marketable crop, offer greater yield stability, reduce fertilizer inputs, suppress weeds, and interrupt disease or pest cycles. Producers increasingly look to radish ( Raphanus sativus L.) as a cover crop, but integrating it into a cropping system with corn ( Zea mays L.) and soybean [ Glycine max (L.) Merr.] has been difficult. Radish following wheat ( Triticum aestivum L.) may provide more options for farmers. Few studies have tested the effects of nitrogen (N) rates on radish production for a dual purpose cover/forage crop or whether additional N is needed because radish is often used to trap N. This study evaluated radish planting date (1 Aug., 15 Aug., 29 Aug., and 11 Sep. in 2012 and 2013) and N fertilizer amount (0, 17, 33, and 67 kg N ha -1 ) on radish heights, chlorophyll content, and biomass production as well as their impact on corn yields the next year (2013 and 2014). Across planting dates and years, non-fertilized controls had shorter radishes than any N rate, while radish chlorophyll content increased as N rates increased. Chlorophyll and biomass content generally did not significantly increase above 33 kg N ha -1 . Radish foliage dry biomass production was 820 to 1670 kg ha -1 greater at the first planting date (1 Aug.) in 2012 and 2013 than the other planting dates. Winter annual weed suppression was greatest at the first planting date in 2012. No differences in winter annual weed suppression were observed in 2013 compared to the other planting dates. Radish planting date did not affect corn yield the following year (2013 and 2014). This study demonstrates the benefits of planting radishes in late summer prior to 1 Sep. and fertilizing with 33 kg N ha -1 for optimum radish biomass production following wheat in upstate Missouri.

The combined effects of fertilizer reduction on high risk areas and increased fertilization on low risk areas, investigated using the SWAT model for a Danish catchment

Some agricultural areas lose considerably more than the average amounts of nutrients to waterways (high risk areas, HRAs) and others considerably less than the average (low risk areas, LRAs). These areas are of great interest when river catchment managers seek to both reduce nutrient loads to lakes and marine areas and to allow intensive agriculture. If HRAs were farmed with decreased inputs of fertilizers the environmental benefit would be larger here than from any other areas, and if LRAs were farmed with increased fertilizer use it could be done here causing less environmental damage than at any other areas. If both these changes were applied within the same catchment they might counter balance each other and give the possibility of intensified farming without causing environmental deterioration. We used the semi-distributed SWAT model to identify both HRAs and LRAs in an intensely farmed lowland catchment in Denmark. These areas are classified as the 10% of the agricultural area leaching, respectively, the most and the least nitrogen. Two scenarios were run for HRAs (reduced fertilizer input by 20%) and LRAs (increased fertilizer input by 20%) separately and two were run where both HRAs and LRAs were included. The scenario results showed that the HRA scenario yielded a decrease (3.3%) in nitrate river load at the catchment scale and that the LRA scenario yielded only a small increase (0.9%). The combined scenarios showed an overall decrease in river nitrate load (2.2%).

Response of Soil Phosphorus Required for Maximum Growth of Asparagus officinalis L. to Inoculation of Arbuscular Mycorrhizal Fungi

Fertilizer application efficiently increases crop yield, but may result in phosphorus (P) accumulation in soil, which increases the risk of aquatic eutrophication. Arbuscular mycorrhizal fungi (AMF) inoculation is a potential method to enhance P uptake by plant and to reduce fertilizer input requirements. However, there has been limited research on how much P application could be reduced by AMF inoculation. In this study, a pot experiment growing asparagus (Asparagus officinalis L.) was designed to investigate the effects of AMF inoculation and six levels of soil Olsen-P (10.4, 17.1, 30.9, 40.0, 62.1, and 95.5 mg kg−1 for P0, P1, P2, P3, P4 and P5 treatments, respectively) on root colonization, soil spore density, and the growth and P uptake of asparagus. The highest root colonization and soil spore density were both obtained in the P1 treatment (76% and 26.3 spores g−1 soil, respectively). Mycorrhizal dependency significantly (P < 0.05) decreased with increasing soil Olsen-P. A significant correlation (P < 0.01) was observed between mycorrhizal P uptake and root colonization, indicating that AMF contributed to increased P uptake and subsequent plant growth. The quadratic equations of shoot dry weight and soil Olsen-P showed that AMF decreased the P concentration of soil required for maximum plant growth by 14.5% from 67.9 to 59.3 mg Olsen-P kg−1. Our results suggested that AMF improved P efficiency via increased P uptake and optimal growth by adding AMF to the suitable P fertilization.

Societal phosphorus metabolism in future coastal environments: Insights from recent trends in Louisiana, USA

Successful adaptation to global environmental change will require confronting multiple unfolding challenges in concert. Coastal regions vulnerable to sea level rise and tropical storms will likely also be influenced by resource limitation in an uncertain future. In this paper, we explore the interrelated dynamics of coastal population migration, economic instability, and anthropogenic phosphorus (P) flows. Accounting for P flows and improving human P use efficiency are critical tasks given the finite global supply of phosphate rock and widespread eutrophication. We use material flow analysis to examine societal P metabolism in the Upper Pontchartrain Basin in coastal Louisiana, USA for two 5-y time periods (2001–2005 and 2006–2010) to capture the effects of fertilizer economics and population growth partially driven by the impact of Hurricane Katrina in the lower basin in 2005. Mass balances encompass human-mediated P fluxes in food production and consumption subsystems across agricultural, developed, and forested landscapes. Drastic reductions in locally purchased inorganic P fertilizer (78% decline between periods) were correlated to increases in fertilizer prices. Total P input to the study region decreased from 5452 to 3268MgPy−1 between periods. Changes in P flows were primarily driven by fertilizer economics, declining dairy production, and the influx of new residents, which has been characterized by decentralized settlement that limits P recycling. Societal P metabolic efficiency increased from 22% to 32% due largely to reduced fertilizer inputs. Leakage to the Pontchartrain Estuary and the Mississippi River represented 17–23% of total system P input, while the vast majority of P accumulated within soils, wastewater systems, and landfills. We discuss basin trends and management implications. A historic opportunity exists to encourage future coastal development characterized by synergies between local agriculture and human habitation to promote energy efficient nutrient recycling. The effect would be a decreased vulnerability to future fertilizer price spikes, along with the mitigation of current and future eutrophication.

Estimating net N mineralization under unfertilized winter wheat using simulations with NET N and a balance approach

Eliminating uncertainty in soil N supply could reduce fertilizer input, but the amount of N mineralized during plant growth is usually still unknown. We aimed to test the relatively simple two-pool net N mineralization model NET N that uses site-specific temperature and soil water functions as well as pedotransfer functions for deriving the pool sizes and was developed for NW Germany. The objectives were to (1) evaluate, if field net N mineralization under unfertilized winter wheat could be satisfactorily simulated, and to (2) examine the variation in time patterns of net N mineralization within years and sites and from two functional N pools: a rather small, fast mineralizable N pool (Nfast) and a much greater, slowly mineralizable N pool (Nslow). NET N simulations for 36 site-year-combinations and up to five dates within the growing season were evaluated with detailed N balance approaches (calculated from: soil mineral N contents, plant N uptake using estimates of green area index, simulated N leaching). Simulated net N mineralization was highly significantly correlated (r2 = 0.58; root mean square error = 24.2 kg N ha−1) to estimations from the most detailed balance approach, with total simulated net N mineralization until mid August ranging from 62.1 to 196.5 kg N ha−1. It also became evident that N mineralization from pool Nslow—in contrast to pool Nfast—was considerably higher for loess soils than for sandy or loamy soils. The results suggest that NET N was adequate for simulations in unfertilized winter wheat. However, further field studies are necessary for proving its applicability under fertilized conditions.

Induced transcriptional profiling of phenylpropanoid pathway genes increased flavonoid and lignin content in Arabidopsisleaves in response to microbial products

BackgroundThe production and use of biologically derived soil additives is one of the fastest growing sectors of the fertilizer industry. These products have been shown to improve crop yields while at the same time reducing fertilizer inputs to and nutrient loss from cropland. The mechanisms driving the changes in primary productivity and soil processes are poorly understood and little is known about changes in secondary productivity associated with the use of microbial products. Here we investigate secondary metabolic responses to a biologically derived soil additive by monitoring changes in the phenlypropanoid (PP) pathway in Arabidopsis thaliana.ResultsThis study was designed to test the influence of one of these products (Soil Builder™-AF, SB) on secondary metabolism after being applied at different times. One time (TI) application of SB to Arabidopsis increased the accumulation of flavonoids compared to multiple (TII) applications of the same products. Fourteen phenolic compounds including flavonols and anothocyanins were identified by mass spectrometry. Kaempferol-3,7-O-bis-α-L-rhamnoside and quercetin 3,7-dirhamnoside, the major compounds, increased 3-fold and 4-fold, respectively compared to control in the TI treatment. The most abundant anthocyanin was cyanidin 3-rhamnoglucoside, which increased 3-fold and 2-fold in TI compared to the control and TII, respectively. Simultaneously, the expression of genes coding for key enzymes in the PP pathway (phenylalanine ammonia lyase, cinnamate 4-hydroxylase, chalcone synthase, flavonoid-3′-O-hydroxylase, flavonol synthase1 and dihydroflavonol-4-reductase) and regulatory genes (production of anthocyanin pigment2, MYB12, MYB113, MYB114, EGL3, and TT8) were up-regulated in both treatments (TI and TII). Furthermore, application of TI and TII induced expression of the lignin pathway genes (hydroxyl cinamyl transferase, caffeyl-CoA O-methyl transferase, cinnamyl alcohol dehydrogenase, cinnamyl-CoA reductase, secondary wall-associated NAC domain protein1, MYB58 and MYB63 resulting in higher accumulation of lignin content compared to the control.ConclusionsThese results indicate that the additions of microbially based soil additives have a perceptible influence on phenylpropanoid pathway gene regulation and its production of secondary metabolites. These findings open an avenue of research to investigate the mode of action of microbially-based soil additives which may assist in the sustainable production of food, feed, fuel and fiber.

Rhizobacteria for reduced fertilizer inputs in wheat (Triticum aestivum spp. vulgare) and barley (Hordeum vulgare) on Aridisols in Turkey

The present study assessed the effect of seed inoculation with single or multiple plant growth-promoting rhizobacterial (PGPR) strains on yield in spring wheat (Triticum aestivum spp. vulgare var. Kirik) and barley (Hordeum vulgare cv. Tokak) plants in both greenhouse and field conditions during the years 2007 and 2008. The treatments of wheat and barley plants during the first year included: (1) Control (no inoculation and no fertilizer), (2) Bacillus OSU-142 (B.OSU-142), (3) Bacillus megaterium M3 (B. megaterium M3), (4) Azospirillum brasilense Sp.245 (A. brasilense Sp.245), (5) Mixed 1 (B.OSU-142 + Bacillus M3 + Azospirillum AB-245), (6) Bacillus megaterium RC07 (B. megaterium RC07), (7) Paenibacillus polymyxa RC05, (8) Bacillus licheniformis RC08, (9) mineral nitrogen N1 (80 kg N ha -1 ) and (10) N2 (40 kg N ha -1 in the form of urea). In the second year treatments were: (1) Raoutella terrigena (R. Terrigena), (2) Burkholderia cepacia FS Tur (B. cepacia FS Tur), (3) B. OSU-142 ARM, (4) B. M3 ARM, (5) A. sp.245 ARM, (6) P. polymyxa RC14, (7) B. megaterium RC10, (8) Mixed 2 (Bacillus OSU-142+ Bacillus M3+ Azospirillum brasilense sp.245 + 40 kg N ha) in addition to the first year treatments. Greenhouse and the two years of field trials at two sites showed that seed inoculation with bacterial strains significantly affected yield, yield components and quality parameters both in spring wheat and barley. In greenhouse trials, single inoculations of seeds with PGPRs gave root and shoot weight increases by 11.0-16.5% and 14.4-30.4% in wheat and by 10.3-18.8% and 11.9-21.5% in barley. Combinations of three bacteria increased root and shoots weight by 18.3-31.5% in wheat and by 21.4-23.8 in barley and bacterial inoculations also increased grain yield by 4.3-18.5% in wheat and 8.3-19.1% in barley, respectively. In field

Recovering root system traits using image analysis exemplified by two-dimensional neutron radiography images of lupine.

Root system traits are important in view of current challenges such as sustainable crop production with reduced fertilizer input or in resource-limited environments. We present a novel approach for recovering root architectural parameters based on image-analysis techniques. It is based on a graph representation of the segmented and skeletonized image of the root system, where individual roots are tracked in a fully automated way. Using a dynamic root architecture model for deciding whether a specific path in the graph is likely to represent a root helps to distinguish root overlaps from branches and favors the analysis of root development over a sequence of images. After the root tracking step, global traits such as topological characteristics as well as root architectural parameters are computed. Analysis of neutron radiographic root system images of lupine (Lupinus albus) grown in mesocosms filled with sandy soil results in a set of root architectural parameters. They are used to simulate the dynamic development of the root system and to compute the corresponding root length densities in the mesocosm. The graph representation of the root system provides global information about connectivity inside the graph. The underlying root growth model helps to determine which path inside the graph is most likely for a given root. This facilitates the systematic investigation of root architectural traits, in particular with respect to the parameterization of dynamic root architecture models.

Biological nitrogen fixation and biomass accumulation within poplar clones as a result of inoculations with diazotrophic endophyte consortia

Sustainable production of biomass for bioenergy relies on low-input crop production. Inoculation of bioenergy crops with plant growth-promoting endophytes has the potential to reduce fertilizer inputs through the enhancement of biological nitrogen fixation (BNF). Endophytes isolated from native poplar growing in nutrient-poor conditions were selected for a series of glasshouse and field trials designed to test the overall hypothesis that naturally occurring diazotrophic endophytes impart growth promotion of the host plants. Endophyte inoculations contributed to increased biomass over uninoculated control plants. This growth promotion was more pronounced with multi-strain consortia than with single-strain inocula. Biological nitrogen fixation was estimated through (15)N isotope dilution to be 65% nitrogen derived from air (Ndfa). Phenotypic plasticity in biomass allocation and branch production observed as a result of endophyte inoculations may be useful in bioenergy crop breeding and engineering programs.

How human diet impacts on waters and resources

Human diet is responsible for a number of environmental problems. It is a driving force for water and land requirements for food production. This contribution investigates the relationships between diet and agricultural production, the resulting mass flows of nitrogen and phosphorus, their impact on the aquatic environment, the agricultural area requirements and emissions of nitrogen to the atmosphere in a clearly defined region. The combination of material flow analysis, nutrient emission model and statistical input data determines the reference state. By changing some input data (changing diet) several independent processes change. Thus the impacts of changing nutrition patterns can be investigated for a well-defined region. According to diet recommendations a scenario was developed and impacts on resources and environment drawn. Application of the method to Austria shows a 30% reduction of agricultural land requirements for food production by changing nutritional habits to a healthy balanced diet. Nitrogen export via rivers would be decreased by 11%. The diet change would also result in a reduced fertilizer input by 6% to agriculture, which is relevant especially for the limited resource phosphorus.

The fate of phosphorus fertilizer in Amazon soya bean fields

Fertilizer-intensive soya bean agriculture has recently expanded in southeastern Amazonia, and whereas intensive fertilizer use in the temperate zone has led to widespread eutrophication of freshwater ecosystems, the effects in tropical systems are less well understood. We examined the fate of fertilizer phosphorus (P) by comparing P forms and budgets across a chronosequence of soya bean fields (converted to soya beans between 2003 and 2008) and forests on an 800 km(2) soya bean farm in Mato Grosso, Brazil. Soya bean fields were fertilized with 50 kg P ha(-1) yr(-1) (30 kg P ha(-1) yr(-1) above what is removed in crops). We used modified Hedley fractionation to quantify soil P pools and found increases in less-plant-available inorganic pools and decreases in organic pools in agricultural soils compared with forest. Fertilizer P did not move below 20 cm. Measurements of P sorption capacity suggest that while fertilizer inputs quench close to half of the sorption capacity of fast-reacting pools, most added P is bound in more slowly reacting pools. Our data suggest that this agricultural system currently has a low risk of P losses to waterways and that long time-scales are required to reach critical soil thresholds that would allow continued high yields with reduced fertilizer inputs.

Assessment of economic and environmental impacts of two typical cotton genotypes with contrasting potassium efficiency

AbstractIt is essential to produce optimal crop yields while reducing adverse environmental impacts of overfertilization. Therefore, nutrient‐efficient plants may play a major role in improving the efficiency of fertilizer use whilst increasing crop yields. This field trial was conducted to study the differences on absorption and utilization of nitrogen (N), phosphorus (P), and potassium (K) of K‐efficient cotton genotype 103 and K‐inefficient cotton (Gossypium hirsutum L.) genotype 122 and their environmental and economic effects. The results show that seed cotton yield was significantly different between K‐efficient cotton genotype 103 and K‐inefficient cotton genotype 122; the yields of genotype 103 were 39.2%, 33.8%, and 25.0% higher than those of genotype 122 with no K fertilizer (K0), 112 kg K ha–1 K (K1), and 224 kg K ha–1 (K2), respectively. Even when no K fertilizer was applied, the yield of genotype 103 was still 7.9% higher than the yield of genotype 122 at the highest K level (K2). Further economic benefit analysis revealed that the value cost ratio (VCR) of genotype 103 was significantly higher than 122 at K0 and K1, and harvest index (HI) of genotype 103 was significantly higher than that of genotype 122 at all three K levels. In addition, when fertilized with K, partial factor productivity of applied K (PFPK) of genotype 103 was dramatically higher than that of genotype 122, demonstrating that genotype 103 had stronger ability to utilize K. Besides, the N‐ and P‐use efficiencies of genotype 103 were also higher than those of genotype 122. It is concluded that: (1) genotype 103 gives better profit than genotype 122 and (2) genotype 103 uses fertilizer more efficiently and reduced fertilizer inputs will alleviate environmental risks.

Influences of Nitrogen and Potassium Fertigation on Nutrient Uptake, Production, and Quality of Pepper Irrigated with Disinfected Urban Wastewater

The use of regenerated water (RW) for irrigation of horticultural crops in the Mediterranean area could contribute to reduce fertilizer inputs, water consumption, and contamination of the environment. The nutrient content of RW and nutrient demand by crops needs to be match to achieve these benefits. This work studies the influence of different levels of nitrogen (N)– potassium (K) fertigation with purified wastewater obtained from Almería city, Spain, on yield, fruit quality, and macronutrient uptake of pepper plants. The experiment was conducted in a polyethylene greenhouse with pepper cv. Aifos, grown on a sand-mulched sandy loam soil using trickle irrigation. The experimental design was randomized blocks with four replicates. Six treatments were applied: two unfertilized controls (RW and ground water, GW) and four NK levels with regenerated water, RW (N1K1, N1K1.5, N1.5K1, and N1.5K1.5). N1K1 is the recommended rate under local conditions, and 125 kg N ha−1 and 193 kg K ha−1 respectively are average nutrient concentrations in fertigation of 9.8 mM N (NO3 − + NH4 +) and 5.4 mM K. The results showed that production parameters were equal in unfertilized RW irrigated plants compared to those irrigated with GW water, both resulting in low commercial production. Fertigation with N1K1 produced yields similar to the RW control. Significant increases in marketable yields, number, and weight of fruit were recorded with N1.5K1.5, N1K1.5, and N1.5K1 rates compared to RW control. The NK level had no effect on fruit quality attributes (pH, fruit firmness, total soluble solids, and titratable acidity of fruit). Nutrient uptake of plants followed the same order in all treatments: K > N > calcium (Ca) > magnesium (Mg) > phosphorus (P). The treatment N1.5K1.5 showed the greatest uptake of N and P, and K uptake was similar to N1K1.5 and N1.5K1 treatments.

Partitioning of net primary production in Eucalyptus and Acacia stands and in mixed-species plantations: Two case-studies in contrasting tropical environments

The introduction of nitrogen fixing species (NFS) in fast-growing tree plantations is an alternative option to reduce fertilizer inputs. However, the success of mixed-species plantations depends on the balance between positive interactions among species (resulting from facilitation and/or complementarity) and the negative effects of interspecific competition.Using a carbon budget approach and coupling measurements of standing biomass, aboveground litterfall and soil CO2 efflux, we assessed the influence of replacing half of eucalypt trees by Acacia mangium on total belowground carbon flux (TBCF), net primary production (NPP) and its partitioning between above- and belowground growth at two tropical sites in Brazil (Itatinga) and in Congo (Kissoko) exhibiting contrasting climates, edaphic conditions and wood productions.Annual soil CO2 efflux (FS) was significantly lower in the acacia monocultures than in eucalypt monocultures and mixed-species stands at both sites. Annual FS was significantly lower at Itatinga compared to Kissoko for all stands while TBCF was significantly lower in the eucalypt stands only. In the eucalypt monocultures we found a significantly lower aboveground NPP (ANPP) and wood production (wood NPP) at Kissoko compared to Itatinga that was almost fully balanced by a significantly higher belowground NPP (BNPP), leading to similar NPP. Similarly, acacia monocultures exhibited significantly higher ANPP and wood NPP at Itatinga than at Kissoko. The mixed-species stands exhibited a significantly lower wood NPP and ANPP than the eucalypt monocultures at the Brazilian site while NPP of the mixture was not significantly different than the average NPP of the two monocultures. At the Congolese site, NPP of the mixture was significantly higher than the average NPP of the two monocultures. NPP was similar in the mixed-species stand and the eucalypt monoculture with a significantly lower partitioning of NPP to belowground production, leading to a one third higher wood biomass at harvest in the mixed-species stand.A positive effect of growing eucalypts with the nitrogen fixing acacia trees on stand wood production occurred at Kissoko but not at Itatinga. Mixed-species plantations with NFS can be advocated at sites where the productive gains resulting from nitrogen fixation are not compromised by other resource limitations.