Fertilizer Agronomic Efficiency Research Articles

Agronomic efficiency of fertilizers with aggregate technology in the Brazilian Eastern Amazon

Agronomic efficiency of fertilizers with aggregate technology in the Brazilian Eastern Amazon

Characteristics and Agronomic Efficiency of Fertilizer Urea Granules- Acidic Coated Bamboo Biochar Acrylate on Plant Onion Red (Allium ascaloniucm L.)

The use of urea-biochar granular fertilizer is intended to overcome the problem of inefficiency in the excessive use of urea fertilizer. The efficiency of urea is relatively low because 40-70% of N is lost from the soil. The purpose of this study was to determine the agronomic efficiency of acrylic acid-coated bamboo urea-biochar fertilizer on shallot plants. The research was conducted in the greenhouse of UPT Plant Pest and Disease Control Center in Celuk Sukawati Gianyar Village, and in the Laboratory of Soil and Environmental Sciences, Faculty of Agriculture, Udayana University, arranged in a Completely Randomized Design with a single factor consisting of 9 treatments and repeated 3 times. Parameters observed were plant growth yields (height, weight of tubers and fresh litter, weight of tubers and oven-dried litter, number of tillers), fertilizer agronomic efficiency. The results showed that the S30 treatment significantly increased the shallot plant height by 43.67 cm, the weight of the oven-dried bulbs by19.68 g and the RAE value by 362%, so that fertilization with the S30 treatment was the most efficient compared to other treatments and could be used by farmers in increasing the growth and yield of shallot plants.

Effects of Nitrogen Reduction at Different Growth Stages on Maize Water and Nitrogen Utilization under Shallow Buried Drip Fertigated Irrigation

A field experiment of drip fertigated nitrogen reduction was set up in a typical Maize planting area in the Xiliao River Basin in 2018 and 2019. Different phased nitrogen reductions were set up under shallow buried drip irrigation during the growth period to explore ways to improve nitrogen use efficiency (NUE) by understanding the Maize regulation of nitrogen absorption and utilization. The recommended nitrogen application in the early stage (Nopt, total nitrogen 240 kg·hm−2) had the highest grain nitrogen uptake and total nitrogen uptake, followed by nitrogen reduction before the maximum canopy mulching (Nde-I, total nitrogen 180 kg·hm−2), nitrogen reduction after the maximum canopy mulching (Nde-II, total nitrogen 180 kg·hm−2) and no nitrogen application (N0). Without nitrogen application, the leaves were thin, green and yellow. The total nitrogen uptake was 38.54~41.31% lower than the recommended nitrogen application in the early stage. When nitrogen fertilizer was reduced in the maximum canopy mulching, grain nitrogen absorption was affected. Grain nitrogen absorption fell by 15.07% to 17.51% when nitrogen was reduced in the maximum canopy mulching compared to the recommended nitrogen application. The harvest index of nitrogen reduction before the maximum canopy coverage was 9.65~11.52% higher than that in the later stage, indicating that the nitrogen absorption between Maize grain, stem, and leaf was better regulated. Maize evapotranspiration water consumption was reduced throughout the growth cycle when nitrogen was reduced at various stages. Nitrogen reduction before maximum canopy mulching boosted water use efficiency (WUE) by 3.44% to 6.12% compared to the recommended nitrogen application in the early stage. The nitrogen fertilizer agronomic efficiency increased by 11.17% to 13.87%. The nitrogen use efficiency rose by 10.99~3.15% (5.24~6.60 percentage points). A total of 25% of nitrogen fertilizer was saved with the yield declining by only about 5%, resulting in increased NUE while maintaining the yield stability. Under shallow buried drip fertigated irrigation, the appropriate reduction in nitrogen fertilizer during the period from Maize sowing to the maximum canopy development ensured the nitrogen supply during tasseling–silking stage and filling stage, which can be used as a regulation method and a way to improve the Maize fertilizer use efficiency.

Effects of phosphorus application rates on photosynthetic and senescence characteristics and yield of diffe-rent stems and tillers of wheat under water-saving supplementary irrigation

To clarify the physiological mechanism underlying grain yield of different stems and tillers of wheat in response to phosphorus application under water-saving supplementary irrigation and to determine the suitable phosphorus fertilization rate, we set water-saving supplementary irrigation (irrigation to the soil water content of 0-40 cm soil layer shall be supplemented to 70% of the field saturation capacity during the jointing stage and flowering stage, W70) and no irrigation (W0) on wheat variety 'Jimai 22', and three phosphorous application rates, low (90 kg P2O5·hm-2, P1), medium (135 kg P2O5·hm-2, P2), and high (180 kg P2O5·hm-2, P3), with no phosphorus application as the control (P0). We examined the photosynthetic and senescence characteristics, the grain yield of the different stems and tillers, as well as water and phosphorus use efficiency. The results showed that under both water-saving supplementary irrigation and no irrigation, the relative content of chlorophyll, net photosynthetic rate, sucrose content, sucrose phosphate synthase activity, superoxide dismutase activity, and soluble protein content of flag leaf of the main stem and tillers Ⅰ and Ⅱ (first degree tillers arising from axils of the 1st and 2nd true leaf of the main stem) under P2 were significantly higher than those under P0 and P1, which contributed to the higher grain weight per spike of main stem and tillersⅠ and Ⅱ, but did not differ from P3. Under water-saving supplementary irrigation, P2 increased grain yield of main stem and tillers Ⅰ, Ⅱ and Ⅲ (first degree tillers arising from axils of the 3rd true leaf of the main stem) compared with that under P0 and P1, and increased grain yield of tillers Ⅱ and Ⅲ compared with P3. Grain yield per hectare under P2 was 49.1%, 30.5% and 8.9% higher than that under P0, P1 and P3, respectively. Similarly, water use efficiency and phosphorus fertilizer agronomic efficiency under P2 were the highest among the phosphorous treatments under water-saving supplementary irrigation. Under no irrigation condition, P2 increased grain yield of main stem and tillers Ⅰ and Ⅱ compared with P0 and P1, yet grain yield of tiller Ⅱ was higher than that of P3. Furthermore, under P2, the grain yield per hectare, water use effi-ciency, and phosphorus fertilizer agronomic efficiency were higher than those under P0, P1 and P3 under no irrigation. Under each phosphorous application rate, grain yield per hectare, phosphorus fertilizer agronomic efficiency, and water use efficiency of water-saving supplementary irrigation treatment were higher than those of no irrigation treatment. In conclusion, medium phosphorus application rate (135 kg·hm-2) under water-saving supplementary irrigation would be the optimal treatment for both high grain yield and efficiency under the experimental condition.

Nitrogen supply improved plant growth and Cd translocation in maize at the silking and physiological maturity under moderate Cd stress

Soil cadmium (Cd) contamination is a serious problem on agricultural land. Adequate nitrogen (N) may help ameliorate plant fitness under Cd stress. This study examined the role of N application in improving maize tolerance to Cd stress. Two maize genotypes, Zhongke11 (larger root system) and Shengrui999 (smaller root system), were grown in a loessal soil amended with Cd (Cd0, no added Cd; Cd1, 20 mg kg−1 soil as CdCl2·2.5 H2O) and N (N0, no added N; N1, 100 mg kg−1 soil as urea) under greenhouse, and plants were assessed at silking and maturity stages. Maize plants exhibited moderate Cd stress with significantly reduced grain yield, especially under low N (N1). Roots accumulated more Cd than above-ground parts. Grain Cd concentration was the least (0.05–0.06 μg g−1) among all organs which is below the safety threshold. Leaf Cd concentrations (0.24–1.18 mg kg−1) were also under the toxicity threshold. Nitrogen addition significantly improved plant growth, chlorophyll content, photosynthesis traits, and tissue Cd contents, and reduced Cd concentration in soil compared to N0 treatment. Nitrogen promoted Cd bioconcentration and translocation factors in stem and leaves. Cadmium stress reduced N fertilizer agronomic efficiency at maturity. At maturity, root Cd content was positively correlated with root N and calcium accumulation, and stem Cd content was positively correlated with stem N content (both P ≤ 0.05). Genotypes with different root system size differed in response to Cd toxicity and / or N deficit. The small-rooted genotype Shengrui999 was more tolerant to moderate Cd stress than the large-rooted Zhongke11. Addition of N ameliorated Cd stress in both maize genotypes by improving plant growth performance, and regulating Cd translocations among plant organs.

Optimization of Nitrogen Fertilizer Application with Climate-Smart Agriculture in the North China Plain

Long−term excessive nitrogen fertilizer input has resulted in several environmental problems, including an increase in N2O emissions and the aggravation of nitrate leaching; monitoring nitrogen fertilizer is crucial for maize with high yield. This study aimed to optimize the amount of nitrogen applied to maize by Climate−Smart Agriculture (CSA) so as to continuously improve agricultural productivity and reduce or eliminate N2O emissions as much as possible. Field experiments with a completely randomized design were conducted to examine the effects of six nitrogen treatments (N application levels of 0, 120, 180, 240, 300, 360 kg·ha−1, respectively) on N2O emissions, residual concentration of nitrate and ammonium nitrogen, maize yield, and nitrogen utilization efficiency in 2018 and 2019. The results indicated that the residual concentration of nitrate nitrogen (NO3-−N) in the two seasons significantly increased; N2O emissions significantly increased, and the nitrogen fertilizer agronomic efficiency and partial productivity of maize fell dramatically as the nitrogen application rate increased. The maize grain yield rose when the N application amount was raised (N application amount <300 kg·ha−1) but decreased when the N application amount > 300 kg·ha−1. An increase in the nitrogen application rate can decrease nitrogen use efficiency, increase soil NO3-−N residual, and N2O emissions. Reasonable nitrogen application can increase maize yield and reduce N2O emissions and be conducive to improving nitrogen use efficiency. By considering summer maize yield, nitrogen use efficiency, and farmland ecological environment, 173.94~178.34 kg N kg·ha−1 could be utilized as the nitrogen threshold for summer maize in the North China Plain.

Exploring the coupling mode of irrigation method and fertilization rate for improving growth and water-fertilizer use efficiency of young mango tree

Unsuitable irrigation and soil nutrient deficiency affect the normal physiology and growth of mango (Mangifera indica L.) of tropical fruit tree in Southwest China. To obtain optimal fertigation mode for mango, the effects of three micro-irrigation methods (i.e., micro-sprinkler irrigation (SI), drip irrigation (DI) and micro-moistening irrigation (MM)) on photosynthetic characteristics, hydraulic conductivity, growth and water-fertilizer use efficiency of young mango tree were investigated under four fertilization rates (i.e., 0 g plant−1 (FN), 9.3 g plant−1 (FL), 18.6 g plant−1 (FM) and 27.9 g plant−1 (FH), a compound water-soluble fertilizer) using a randomized block design experiment. The results indicated that DI and MM increased net photosynthetic rate (Pn) by 17.50 and 28.95%, root hydraulic conductivity (Kr) by 39.65 and 52.69%, shoot hydraulic conductivity (Ksh) by 48.63 and 82.38%, total dry mass (DM) by 27.44 and 47.13%, water use efficiency (WUEET) by 43.27 and 73.17%, fertilizer agronomic efficiency (FAE) by 45.92 and 95.41%, and partial factor productivity of fertilizer (PFP) by 33.96 and 54.44%, but reduced transpiration rate (Tr) by 6.61 and 16.38%, leaf with petiole hydraulic conductivity (Kl+p) by 13.11 and 30.32%, and water consumption (ET) by 10.38 and 14.85% when compared with SI. Compared with FN, enhancing fertilization rate significantly increased Pn, Tr, total hydraulic conductivity (root to leaf), total DM, healthy index (Hi) and WUEET, and their maximum values appeared in the FM. FAE firstly increased and then decreased, while PFP gradually reduced with the increase of fertilization rate. MMFM had the highest total DM and WUEET, 2.32 and 2.58 times of SIFN (CK), and the largest FAE of 4.95 kg−1. Thus, MMFM (micro-moistening irrigation with moderate fertilization rate of 18.6 g plant−1) significantly promoted growth and improved water-fertilizer use efficiency of young mango tree, which was the best coupling mode of irrigation method and fertilization rate.

Effects of fertilizer application on yield and fertilizer utilization of Coffea arabica in southwest dry-hot region of China under different shading levels

The fertilizer and shading management of Coffea arabica in dry-hot area is extensive, resulting in lower yield and fertilizer utilization efficiency. A field experiment was carried out to find the coupling mode of shading and fertilizer for fertilizer-saving and high yield of C. arabica in dry-hot region. Four shading levels (100% NR, 75% NR, 60% NR, 45% NR, NR was natural radiation) and four fertilizer levels (No fertilization and 666.67, 1000, 1333.33 kg·hm-2) were set to examine the effects of different radiations and fertilizer treatments on canopy structure, yield, ferti-lizer use efficiency, soil nutrient content and microbial biomass carbon of C. arabica. The results showed that canopy structure, yield, fertilizer use efficiency, soil nutrient content and microbial biomass carbon were significantly affected by shading and fertilizer treatments. Soil nutrient content and microbial biomass carbon decreased with the increases of shading levels. Soil nutrient content increased with the increases of fertilizer application, while microbial biomass carbon increased first and then decreased, with a peak at the rate of 1000 kg·hm-2(200.30 mg·kg-1). Shading and fertilizer had significant effects on the canopy structure including leaf area index and openness. There were significant negative correlations of leaf area index with openness, gap fraction, total fixed-point factor and total radiation under canopy. Results of response surface analysis and spatial analysis showed that the combination of shading level and fertilizer application were 80% NR and 666.67 kg·hm-2, 79% NR and 1286.81 kg·hm-2, 79% NR and 967.74 kg·hm-2, 82% NR and 1075.27 kg·hm-2, respectively, when partial fertilizer productivity, yield, fertilizer agronomic efficiency and yield increase of fertilizer reached the maximum. The ranges of shading and fertilizer were 68%-77% NR and 946.24-1178.79 kg·hm-2 when the yield, agronomic efficiency and yield increasing rate by fertilizer reached 80% of the maximum value. In this experiment, the optimum combination of shading level and fertilizer application was 75% NR and 1000 kg·hm-2.

Agronomic efficiency of fertilizers in pea growing under the conditions of climate change of the Black Sea Steppe

Agronomic efficiency of fertilizers in pea growing under the conditions of climate change of the Black Sea Steppe

Effects of combined application of pig manure with urea on grain yield and nitrogen utilization efficiency in rice-wheat rotation system

To examine the effects of pig manure application on dry matter production, nitrogen accumulation and distribution, grain yield and nitrogen use efficiency of rice and wheat, the field trial was conducted with wheat 863 and rice 498. Fertilization treatments consisted of seven rates of organic manure supply: control (CK, no chemical nitrogen fertilizer, no pig manure), conventional fertilizing (T1, no pig manure), 2500 kg·hm-2 pig manure with 75% conventional fertilizing (T2), 5000 kg·hm-2 pig manure with 50% conventional fertilizing (T3), 10000 kg·hm-2 pig manure (T4), 15000 kg·hm-2 pig manure (T5) and 20000 kg·hm-2 pig manure (T6). Combined application of pig manure with chemical fertilizer promoted dry matter accumulation of rice and wheat throughout the growing season. At the maturity stage of rice and wheat, the highest aboveground dry matter accumulation presented under highest pig manure input (T6). The dry matter accumulation and nitrogen distribution were enriched in stem or leaf. The dry matter accumulation and nitrogen distribution rate in grain at T6 was significantly lower than T2 treatment. The high-est nitrogen fertilizer partial productivity, fertilizer agronomic efficiency and grain yield of rice pre-sented at T3 treatment, which increased by 11.4%, 55.4%, 11.4% than that of conventional chemical fertilizer treatment, respectively. These vaules for wheat were at T2, which was 14.0%, 29.1%, 14.0% higher than that of conventional fertilizer treatment, respectively. The combined application of pig manure with appropriate rates of chemical fertilizer (T2 and T3) could promote dry matter accumulation, the migration of nitrogen to grains, the increase of yield and the nitrogen use efficiency. Too much pig manure input (15000-20000 kg·hm-2) could lead to excessive supply of nitrogen for crops. In this case, the transportation of dry matter to economic organs would be blocked and the nitrogen enriched to stem. The late-maturing phenomenon occurred, resulting in significant decrease of grain yield.

Yield and water use responses of winter wheat to irrigation and nitrogen application in the North China Plain

With increasing water shortage resources and extravagant nitrogen application, there is an urgent need to optimize irrigation regimes and nitrogen management for winter wheat (Triticum aestivum L.) in the North China Plain (NCP). A 4-year field experiment was conducted to evaluate the effect of three irrigation levels (W1, irrigation once at jointing stage; W2, irrigation once at jointing and once at heading stage; W3, irrigation once at jointing, once at heading, and once at filling stage; 60 mm each irrigation) and four N fertilizer rates (N0, 0; N1, 100 kg N ha−1; N2, 200 kg N ha−1; N3, 300 kg N ha−1) on wheat yield, water use efficiency, fertilizer agronomic efficiency, and economic benefits. The results showed that wheat yield under W2 condition was similar to that under W3, and greater than that under W1 at the same nitrogen level. Yield with the N1 treatment was higher than that with the N0 treatment, but not significantly different from that obtained with the N2 and N3 treatments. The W2N1 treatment resulted in the highest water use and fertilizer agronomic efficiencies. Compared with local traditional practice (W3N3), the net income and output-input ratio of W2N1 were greater by 12.3 and 19.5%, respectively. These findings suggest that two irrigation events of 60 mm each coupled with application of 100 kg N ha−1 is sufficient to provide a high wheat yield during drought growing seasons in the NCP.

Maize and pigeon pea sole crop and intercrop nutrient response functions for Tanzania

Low soil fertility constrains crop productivity in Tanzania. Fertilizer recommendations were lacking for pigeon pea (Cajanus cajan (L.) Millsp.) sole crop (PPSC) and intercrop. Trials were conducted in eastern and northern Tanzania to determine: maize (Zea mays L.) (MSC), PPSC and intercrop (MzPpI) nutrient response functions; the agronomic and economic efficiency for applied nutrients; other nutrient deficiencies; and a means of calculating MzPpI response functions from MSC functions. The treatment structure allowed for determination of MSC and MzPpI response functions for N, P and K and of PPSC functions for P and K. Overall mean PPSC yield was 2.31 Mg ha−1 with a 12% increase due to applied P. Yield of MSC was increased by N only and of MzPpI by N and P, although intercropped pigeon pea yield was not affected by nutrient application. Yields were not increased with K, Mg, S, Zn, and B application. Yield of MzPpI, as maize grain value equivalent, was more than with MSC but response to N were similar. The agronomic efficiency of fertilizer N at the economically optimal rate (EOR) for MSC was 32 kg kg−1. The EOR of N were similar for MSC and MzPpI and was on average 27 kg ha−1 less for the most compared with the least costly fertilizer N scenario with 3% less yield with the lower EOR. The coefficients for MzPpI N and P response functions can be estimated from MSC functions, hence reducing field research requirements for optimization of fertilizer use for MzPpI.

Management of textile wastewater for improving growth and yield of field mustard (Brassica campestris L.)

ABSTRACTDisposal of industrial wastewater is a current issue of urbanization. However, this problem can be sorted out by using wastewater as an alternate source of irrigation after the addition of some amendment. In this way, the problem of disposal of wastewater not only will be resolved but also scarcity of irrigation water can be kept off in the future. The current research study was performed to evaluate the influence of different concentrations of wastewater along with canal water for enhancing growth and yield of field mustard. Plants were irrigated with different mixtures of canal water and wastewater (75:25, 50:50, 25:75, and 00:100) in addition to canal water as control. The results revealed that application of 50:50% waste and canal water improved plant height, the number of pods plant−1, pod length, root length, root dry weight, shoot dry weight, 100 grain weight, grain and biomass yield plant−1, and nitrogen, phosphorus, and potassium concentration in grain and straw up to 16%, 15%, 17%, 29%, 15%, 56%, 25%, 41%, 35%, 20%, 52%, 45%, 20%, 44%, and 42%, respectively, over positive control treatment. While, nutrient uptakes and agronomic efficiency of fertilizers also improved by the application of 50:50% canal and wastewater compared to positive control treatment. Furthermore, the concentration of heavy metals, predominantly Cr, Cu, Cd, and Pb, was reduced in grains by application of 50% canal water and 50% wastewater. The outcomes suggest that wastewater utilization along with canal water mixing might be an effective approach for enhancing growth and yield of field mustard.

Effect of tobacco straw incorporation on rice yield and nutrient absorption and its substitute for potassium fertilizer

Field trails were carried to study the effects of tobacco straw incorporation and potassium (K) fertilizer on rice yield, K uptake and use efficiency, and its substitute for K fertilizer under different paddy soil K levels in tobacco-rice rotation areas. Results showed that both tobacco straw incorporation (2250 kg·hm-2) and K fertilizer application (75 kg K2O ·hm-2) could increase grain yield and aboveground K uptake of rice. The treatment of tobacco straw incorporation with K fertilizer (St+NPK) got the best effect on rice yield compared with the control (NP). In this treatment (St+NPK), rice yields were increased by 13.3%, 17.1% and 13.5% for low-K soil (available potassium content < 100 mg·kg-1), middle-K soil (available potassium content 100-150 mg·kg-1) and high-K soil (available potassium content > 150 mg·kg-1), respectively, compared with NP. Tobacco straw incorporation (St+NP) could increase K fertilizer recovery efficiency and K fertilizer agronomic efficiency. Under the current practice of applying 75 kg K2O·hm-2, St+NPK showed no significant effect on K fertilizer recovery efficiency and K fertilizer agronomic efficiency, demonstrating that the recommended rate of K fertilizer might be more than the actual demand of rice growth. More importantly, data of tobacco straw substitute for K fertilizer showed that tobacco straw incorporation could replace 10%-22% K fertilizer during rice growing season, i.e. K fertilizer could be reduced by 7.2-16.5 kg·hm-2 for rice under the condition of tobacco straw incorporation. Therefore, it was suggested that straw incorporation could reduce the rate of K fertilizer for high-K soil, but the current K fertilizer inputs (75 kg K2O·hm-2) should be supplied to get high rice yield and maintain the soil potassium balance for low-K soil and middle-K soil.

English

Two trials with the combined effects of seeding density and application of DAP fertilizer on the yield of four biofortified bean varieties were carried out in Kashusha on the experimental site of the Universit&eacute; Evang&eacute;lique en Afrique during the 2013-2014 agricultural long rains season (September-January) and short rains season (March-May). The overall objective was to investigate the response of biofortified common bean and its response to seeding density, mineral fertilizer application, and good agricultural practices. Four bean varieties were used (RWK-10, HM 21-7, CODMLB001 and RWR2245) and the experimental design was split-split plot whose main plot was occupied by varieties and sub-plots had DAP fertilizer crossed with two seeding spacing. Two seeding densities were considered, 250,000 plants ha-1 and 500,000 plants ha-1 respectively corresponding to the spacing between plants 40 cm x 20 cm (commonly used) and 20 cm x 20 cm. The plot was divided into 3 blocks (or repetitions), distant of 2 m and each comprising two sub-blocks separated by 1 m. A sub-block was treated with fertilizer (DAP) and the other was kept as control. The yield of bean seeds has varied from one season to another independently of varieties, which had no effect. It was better in long rains season (1725 kg ha-1) than in short rains season (1087.4 kg ha-1). The effect of fertilizer was also dependent on the season, no effect was observed in short rains season, with huge poorly distributed rains. However, in long rains season, the application of DAP has produced a high number of pods per plant and large grains leading to a higher yield of 1368.6 kg ha-1 when the fertilizer was applied compared to control which produced only 806.1 kg ha-1. During the same season, doubling the density, a yield of 1842.9 kg ha-1 was obtained compared to the density of 250,000 plants ha-1 that produced 1607.1 kg ha-1. The agronomic efficiency of fertilizer was low, ranging from 1.53 for the CODMLB001 variety to 5.64 for HM21-7 variety. Multi-local trials, in contrasting environments are needed to better understand the influence of the season on the bean behaviour in dissemination in South Kivu. It is also interesting to test other seeding densities, fertilizer types and doses for adequate recommendation of fertilization of this crop in Kabare territory. Due to low soil pH, it should be important for example to apply lime before applying the fertilizer. Key words: Bean, seedling density, Di-ammonium phosphate (DAP), variety, yield &nbsp

Variable rate fertilization in citrus: a long term study

Variable rate technology allows application of inputs according to the field spatial variability. Citrus fields can be significantly variable in either soil or plant aspects. Thus, variable rate fertilization seems to be an adequate approach to deal with this issue. However, its effects on input consumption, yield and other crop factors have not yet been assessed during long term experiments. The objective of this study was to evaluate the effects of variable rate fertilization on the input consumption, soil fertility and yield during a long term experiment in citrus. A strip experiment was established in two 25 ha citrus fields in Sao Paulo, Brazil, to compare variable rate against uniform rate fertilization. This experiment was carried out during 6 years. Variable rate prescriptions were based on soil and leaf grid sampling and on yield maps. Uniform applications were based on conventional soil sampling and average yield data. Variable rate treatment resulted in significant reduction in input consumption, but different soil fertility and yield responses were obtained by the variable rate in each field. Field 1 presented higher variability regarding soil and topography. Variable rate application resulted in a better soil fertility management and yield increase in this field. Field 2, which was less variable regarding soil and topography, got poorer results from variable rate treatment regarding soil fertility and yield response. Either way, variable rate technology resulted in higher fertilizer agronomic efficiency in both fields. N, P, and K fertilizers resulted in more fruit yield when applied site-specifically.

Integrated soil fertility management in sub-Saharan Africa: unravelling local adaptation

Abstract. Intensification of smallholder agriculture in sub-Saharan Africa is necessary to address rural poverty and natural resource degradation. Integrated soil fertility management (ISFM) is a means to enhance crop productivity while maximizing the agronomic efficiency (AE) of applied inputs, and can thus contribute to sustainable intensification. ISFM consists of a set of best practices, preferably used in combination, including the use of appropriate germplasm, the appropriate use of fertilizer and of organic resources, and good agronomic practices. The large variability in soil fertility conditions within smallholder farms is also recognized within ISFM, including soils with constraints beyond those addressed by fertilizer and organic inputs. The variable biophysical environments that characterize smallholder farming systems have profound effects on crop productivity and AE, and targeted application of agro-inputs and management practices is necessary to enhance AE. Further, management decisions depend on the farmer's resource endowments and production objectives. In this paper we discuss the "local adaptation" component of ISFM and how this can be conceptualized within an ISFM framework, backstopped by analysis of AE at plot and farm level. At plot level, a set of four constraints to maximum AE is discussed in relation to "local adaptation": soil acidity, secondary nutrient and micronutrient (SMN) deficiencies, physical constraints, and drought stress. In each of these cases, examples are presented whereby amendments and/or practices addressing these have a significantly positive impact on fertilizer AE, including mechanistic principles underlying these effects. While the impact of such amendments and/or practices is easily understood for some practices (e.g. the application of SMNs where these are limiting), for others, more complex processes influence AE (e.g. water harvesting under varying rainfall conditions). At farm scale, adjusting fertilizer applications to within-farm soil fertility gradients has the potential to increase AE compared with blanket recommendations, in particular where fertility gradients are strong. In the final section, "local adaption" is discussed in relation to scale issues and decision support tools are evaluated as a means to create a better understanding of complexity at farm level and to communicate appropriate scenarios for allocating agro-inputs and management practices within heterogeneous farming environments.

Management of Furrow Irrigation and Nitrogen Application on Summer Maize

The efficient use of water and N represents a primary concern to agricultural production in Northwest China. The objective of this study was to assess the impacts of irrigation and fertilization on water and N use, soil volatilized NH3, soil NO3 leaching, and NO3 transfer in soil profiles. A 2‐yr field experiment was conducted to assess the separation of N fertilizer and water with alternating furrow irrigation (SNWAFI) and conventional irrigation and fertilization (CIF) in a maize (Zea mays L.) production system. The yields with SNWAFI were 10 to 16% greater than with CIF. Compared with CIF, SNWAFI increased water use efficiencies (WUEs) by 13 to 33%, agronomic efficiency of fertilizer N by 36 to 56%, and NO3−–N in the upper soil layers (0–60 cm) by 30 to 60%. However, SNWAFI reduced NO3−–N in the deeper soil layers (60–200 cm) by 8 to 44% compared with CIF. The use of SNWAFI also decreased soil NH3 emission with the combination with lower irrigation (40 mm) and N rate (100 kg N ha−1), which indicated that SNWAFI emitted less soil NH3 than CIF. Therefore, compared with CIF, SNWAFI increased maize yield WUE and N use efficiency, reduced N leaching, and curtailed soil NH3 loss with appropriate irrigation and N rates. The use of SNWAFI, leading to better spatial management of irrigation water and N application, can provide both agronomic and environmental benefits.

Extractants to assess zinc phytoavailability in mineral fertilizer and industrial by-products

Efficient analytical methods for the quantification of plant-available Zn contained in mineral fertilizers and industrial by-products are fundamental for the control and marketing of these inputs. In this sense, there are some doubts on the part of the scientific community as well as of the fertilizer production sector, whether the extractor requested by the government (Normative Instruction No. 28, called 2nd extractor), which is citric acid 2 % (2 % CA) (Brasil, 2007b), is effective in predicting the plant availability of Zn via mineral fertilizers and about the agronomic significance of the required minimal solubility of 60 % compared to the total content (HCl) (Brasil, 2007a). The purpose of this study was to evaluate the alternative extractors DTPA, EDTA, neutral ammonium citrate (NAC), buffer solution pH 6.0, 10 % HCl, 10 % sulfuric acid, 1 % acetic acid, water, and hot water to quantify the contents of Zn available for maize and compare them with indices of agronomic efficiency of fertilizers and industrial by-products when applied to dystrophic Clayey Red Latosol and Dystrophic Alic Red Yellow Latosol with medium texture. The rate of Zn applied to the soil was 5 mg kg-1, using the sources zinc sulfate, commercial granular zinc, ash and galvanic sludge, ash and two brass slags. Most Zn was extracted from the sources by DTPA, 10 % HCl, NAC, 1% acetic acid, and 10 % sulfuric acid. Recovery by the extractors 2 % CA, EDTA, water, and hot water was low. The agronomic efficiency index was found to be high when using galvanic sludge (238 %) and commercial granular zinc (142 %) and lower with brass slag I and II (67 and 27 %, respectively). The sources galvanizing ash and brass ash showed solubility lower than 60 % in 2 % CA, despite agronomic efficiency indices of 78 and 125 %, respectively. The low agronomic efficiency index of industrial by-products such as brass slag I and galvanizing ash can be compensated by higher doses, provided there is no restriction, as well as for all other sources, in terms of contaminant levels of arsenic, cadmium, chromium, lead, and mercury as required by law (Normative Instruction No 27/2006). The implementation of 2nd extractor 2 % CA and the requirement of minimum solubility for industrial by-products could restrict the use of alternative sources as potential Zn sources for plants.

Nitrogen Use Efficiency of Irrigated Corn for Three Cropping Systems in Nebraska

Nitrogen use efficiency (NUE) is of economic and environmental importance. Components of NUE were evaluated at in 32 irrigated corn (Zea mays L.) trials conducted across Nebraska with different N rates and where the previous crop was either corn (CC), drybean (Phaseolus vulgaris L.) (CD), or soybean [Glycine max (L.) Merr.] (CS). The mean grain yield with adequate nutrient availability was 14.7 Mg ha−1 When no N was applied, measured soil properties and irrigation water N accounted for &lt;20% of the variation in plant nitrogen uptake (UN). Mean fertilizer N recovery in aboveground biomass was 74% at the lowest N rate compared with 40% at the highest N rate, a mean of 64% at the economically optimal nitrogen rate (EONR), and least with CD. Agronomic efficiency of fertilizer N averaged 29 kg grain kg−1 N at EONR and was also least with CD. Partial factor productivity of N averaged 100 kg grain kg−1 N at EONR, and was greater with CS compared with CC and CD. After harvest, residual soil nitrate nitrogen (RSN) in the 0‐ to 1.2‐m depth ranged from 21 to 121 kg ha−1 and increased with N rate. Mean RSN was 88, 59, and 59 kg ha−1 for CD, CC, and CS, respectively. High corn yields can be achieved with high NUE and low RSN by management to maximize profitability in consideration of yield potential, and by applying N at the right amount and time.