Enhancing phosphorus availability,soil organic carbon,maize productivity and farm profitability through biochar and organic–inorganic fertilizers in an irrigated maize agroecosystem under semi‐arid climate

Biochar amendments offer promising potential to improve soil fertility, soil organic carbon (SOC) and crop yields; however, a limited research has explored these benefits of biochar in the arid and semi‐arid regions. This two‐year field study investigated the effects of Acacia tree biomass‐derived biochar, applied at 0 and 10 t ha^?1 rates with farmyard manure (FYM) or poultry manure (PM) and mineral phosphorus (P) fertilizer combinations (100 kg P ha^‐1), on maize (Zea mays L.) productivity, P use efficiency (PUE) and farm profitability. The application of biochar with organic–inorganic P fertilizers significantly increased soil P and SOC contents than the sole organic or inorganic P fertilizers. Addition of biochar and PM as 100% P source resulted in the highest soil P (104% increase over control) and SOC contents (203% higher than control). However, maize productivity and PUE were significantly higher under balanced P fertilizer (50% organic + 50% mineral fertilizer) with biochar and the increase was 110%, 94% and 170% than 100%‐FYM, 100%‐PM and 100% mineral fertilizer, respectively. Maize productivity and yield correlated significantly positively with soil P and SOC contents These positive effects were possibly due to the ability of biochar to improve soil properties, P availability from organic–inorganic fertilizers and SOC which resulted in higher PUE and maize productivity. Despite the significant positive relationship of PUE with net economic returns, biochar incorporation with PM and mineral fertilizer combination was economically profitable, whereas FYM along biochar was not profitable due to short duration of the field experiments.     

Nitrogen and Phosphorus Availability in Groundfish Waste and Chitin-Sludge Cocomposts

Seafood processing generates a substantial volume of wastes. This study examined the feasibility of converting the fish waste into useful fertilizer by composting. Groundfish waste and chitin sludge generated from the production of chitin were composted with red alder or a mixture of western hemlock and Douglas-fir sawdust to produce four composts: alder with groundfish waste (AGF); hemlock/fir with groundfish waste (HGF); alder with chitin sludge (ACS); and hemlock/fir with chitin sludge (HCS). The resulting AGF had a higher total N and a lower C:N ratio than the other three composts. A large portion of the total N in the AGF, HGF, and HCS composts was in inorganic forms (NH₄⁺-N and NO₃^?-N), as opposed to only two percent in the ACS compost. Alder sawdust is more quickly decomposed, which favored N retention and limited nitrification during the composting period. It was less favorable than the hemlock/Douglas fir sawdust for composting with chitin sludge. Corn growth on soil amended with compost was dependent upon both compost type and rate. Nitrogen and P availabilities in all composts except the ACS were high and compost addition enhanced corn yields, tissue N and P concentrations, and N and P up-take. Neither the total N concentration nor the C:N ratio of the composts was an effective measure of compost N availability in the soil. Because soil inorganic N test levels correlated well with the corn biomass, tissue N and N uptake, they should be an effective measure of the overall compost effects on soil N availability and corn growth response. Phosphorus concentration, which increased linearly with increasing compost rates, was related to soil P availability from compost additions and correlated well with corn biomass, tissue P concentration and P uptake under uniform treatments of N and K fertilizers. Composting groundfish waste with alder or hemlock/Douglas-fir sawdust can produce composts with sufficient amounts of available N and P to promote plant growth and is considered to be a viable approach for recycling and utilizing groundfish waste.     

Short‐term and residual availability of nitrogen after long‐term application of organic fertilizers on arable land

Knowledge on short‐term and long‐term availability of nitrogen (N) after application of organic fertilizers (e.g., farmyard manure, slurry, sewage sludge, composts) provides an important basis to optimize fertilizer use with benefits for the farmer and the environment. Nitrogen from many organic fertilizers often shows little effect on crop growth in the year of application, because of the slow‐release characteristics of organically bound N. Furthermore, N immobilization after application can occur, leading to an enrichment of the soil N pool. However, this process finally increases the long‐term efficiency of organic fertilizers. Short‐term N release from organic fertilizers, measured as mineral‐fertilizer equivalents (MFE), varies greatly from 0% (some composts) to nearly 100% (urine). The most important indicators to be used for predicting the short‐term availability of N are total and NH ‐N contents, C : N ratio (especially of the decomposable organic fraction), and stability of the organic substances. Processing steps before organic fertilizers are applied in the field particularly can influence N availability. Composting reduces mineral‐N content and increases the stability of the organic matter, whereas anaerobic fermentation increases NH ‐N content as well as the stability of organic matter, but decreases the C : N ratio remarkably, resulting in a product with a high content of directly available N. Nevertheless, long‐term effects of organic fertilizers rather slowly releasing N have to be considered to enable optimization of fertilizer use. After long‐term application of organic fertilizers, the overall N‐use efficiency is adequate to a MFE in the range of 40%–70%.     

Fertilizer value of phosphorus in different residues

The phosphorus (P) fertilizer effect of a range of commonly available manure, waste treatment and by‐product residues was tested in pot, field and incubation experiments. The effect of the residues on P offtake was compared with that of commercial mineral P (super phosphate) to calculate the mineral fertilizer equivalent (MFE). Possible relationships between MFE and P extractable from residues using different agents (ammonium lactate, citrate, water) were examined. Dry matter yield and P concentration were measured in ryegrass grown in pots amended with 14 different residues. The effect on the first cut (after 5 weeks) was significantly higher for residues with a low organic matter content, for example ash and biogas residues (MFE = 74–85%), than for many other products with higher organic matter content, for example meat meal (MFE = 44%), cattle slurry (MFE = 57%) and sewage sludge (MFE = 0–37%). However, the effect on two combined cuts (after 11 weeks) was more similar between residues (MFE = 40–60% for most residues). Ammonium lactate‐extractable P (P‐AL) in residues correlated better with MFE (r² = 0.48) than water‐extractable or citrate‐extractable P. Grain yield and P concentration were measured in a field experiment with spring wheat fertilized with four different residues. Pelleted meat meal had a similar effect on yield and P offtake as mineral fertilizer P, whereas two different sewage sludge and chicken manure had approximately 50% of the mineral fertilizer effect. The effect of residues on soil P‐AL (the Swedish measure of easily available soil P) in the incubation experiment showed no correlation with MFE from the pot experiments.     

Wood ash effects on chemical and microbiological properties of digestate- and manure-amended soils

A field study was carried out to evaluate the potential of wood ash as a fertilizer in grassland systems in combination with enriched N organic wastes. Six treatments including manure or digestate, each combined with wood ash at 0, 1, and 3 t?ha^?1 were spread onto the soil to an amount equivalent to 120 kg?N ha^?1. Three soil samplings and one cutting was carried out within one growing season (3 months). A higher pH value was found in manure-treated plots, the pH rise being proportional to the amount of wood ash added. Those plots amended with digestate were characterized by a larger content of total C, NH₄ ⁺, and total P (TP) regardless of the amount of ashes. Microbial activity, assessed by basal respiration and microbial biomass carbon of the differently treated soils, was not affected neither by the nature of the organic waste nor by the amount of wood ash added. However, amending soil with digestate resulted in a more efficient soil microbial community, as shown by the lower values of the metabolic quotient. Such effects were accompanied by a higher percentage of plant cover, particularly of leguminous plants in digestate-treated plots. The time of sampling (seasonal effects) was found to influence the soil pH and electrical conductivity (EC), as well as the nutrient content (total N, NH₄ ⁺, and NO₃ ^?). Overall, the combined use of wood ash and biogas digestate can constitute an efficient way for the disposal and recycling of both products and additionally, it may constitute an environmentally friendly alternative to mineral fertilizers for acid soils.     

Biochar‐Based Fertilization with Liquid Nutrient Enrichment: 21 Field Trials Covering 13 Crop Species in Nepal

Biochar produced in cost‐efficient flame curtain kilns (Kon‐Tiki) was nutrient enriched either with cow urine or with dissolved mineral (NPK) fertilizer to produce biochar‐based fertilizers containing between 60–100 kg N, 5–60 kg P₂O₅ and 60–100 kg K₂O, respectively, per ton of biochar. In 21 field trials, nutrient‐enriched biochars were applied at rates of 0·5–2 t ha⁻¹ into the root zone of 13 different crops. Treatments combining biochar, compost and organic or chemical fertilizer were evaluated; control treatments contained same amounts of nutrients but without biochar. All nutrient‐enriched biochar substrates improved yields compared with their respective no‐biochar controls. Biochar enriched with dissolved NPK produced on average 20% ± 5·1% (N  = 4 trials) higher yields than standard NPK fertilization without biochar. Cow urine‐enriched biochar blended with compost resulted on average in 123% ± 76·7% (N  = 13 trials) higher yields compared with the organic farmer practice with cow urine‐blended compost and outcompeted NPK‐enriched biochar (same nutrient dose) by 103% ± 12·4% (N  = 4 trials) respectively. Thus, the results of 21 field trials robustly revealed that low‐dosage root zone application of organic biochar‐based fertilizers caused substantial yield increases in rather fertile silt loam soils compared with traditional organic fertilization and to mineral NPK or NPK‐biochar fertilization. This can be explained by the nutrient carrier effect of biochar, causing a slow nutrient release behaviour, more balanced nutrient fluxes and reduced nutrient losses, especially when liquid organic nutrients are used for the biochar enrichment. The results open up new pathways for optimizing organic farming and improving on‐farm nutrient cycling. Copyright © 2017 John Wiley & Sons, Ltd.     

Characterizing phosphorus availability in waste products by chemical extractions and plant uptake

Background: The fertilizer value of phosphorus (P) in waste products relies heavily on its availability to the subsequent crop. Aim: We studied the link between extractable P in waste products and apparent P recovery (APR, i.e., difference in plant P uptake between P amended and un‐amended soils divided by the amount of P added) using spring barley grown on three sandy soils. Methods: The products included sewage sludge, biomass ash, struvite, compost, meat and bone meal, biochar from sewage sludge, and industrial sludge. Soft rock phosphate and triple‐superphosphate (TSP) were included for comparison. Availability of P was characterized by extraction with water and solutions of sodium bicarbonate, citric acid, oxalic acid, hydrochloric acid, ammonium acetate, ammonium fluoride and anion exchange resin membranes. TSP was used to establish mineral‐fertilizer‐equivalents (MFE). Water and bicarbonate extractions were also applied to products incubated with soil before extraction. Results: The APR ranged 26 to 31% for TSP and 0 to 30% for waste products. APR correlated most strongly with bicarbonate extractable P. The correlation increased when products were incubated with soil before extraction. Conclusions: We conclude that bicarbonate extraction is a good indicator of potential P availability. However, interactions between waste products and soil properties modify P availability.     

Sewage sludge as a fertilizer of pole stage forests: short-term hydrochemical fluxes and foliar response

Abstract. Proposed restrictions on the disposal of sewage to the marine environment means that alternative land based outlets are required in the UK. Commercial forestry represents a significant land use that could receive and benefit from the application of sewage sludge, to overcome the generally poor soil nutrient status. The oligotrophic and sensitive nature of surface waters in many afforested areas requires that the environmental consequences of the widespread use of organic fertilizers in forestry are carefully considered. This paper compares the effects of an N and P fertilizer with that of sewage sludge on the nutrient content of foliage in a pole stage Scots pine ( Pinus sylvestris ) forest and of nutrient fluxes in soil. Both conventional fertilizer and sewage treatments had significant but differing effects on the availability and leaching of the major nutrients, especially N and P. Evidence for increased nitrification and nitrate production with time was apparent for both treatments. Fluxes of N and P in mineral horizon leachate were consistently smaller than those from the overlying organic horizon. Foliar nutrient concentrations after one year were significantly higher ( P < 0.01) in all of the treatments, and conventional fertilization with urea produced a significantly higher foliar N concentration than that measured in the sludge-treated plots. There was no evidence for appreciable N or P leaching from the site within a year of sludge application.     

Mineral‐nutrient synergism and dilution responses to nitrogen fertilizer in field‐grown maize

Nitrogen (N)‐fertilizer applications to field‐grown maize may result in a dilution response whereby essential mineral‐element concentrations in shoots would decrease as shoot‐dry‐matter accumulation increased. To investigate this, the effect of N‐fertilizer treatments (no N or fertilizer rate based upon 5.3 or 8.5 t ha^–1 yield goal) on maize (Zea mays L.) shoot dry weight and shoot mineral concentrations (N, P, K, S, Mg, Ca, and Mn) at the sixth leaf (V6), twelfth leaf (V12), and tassel (VT) development stages were investigated in a 2‐year study conducted at Brookings, South Dakota (USA). With increasing N‐fertilizer application rates, shoot dry weight was greater and shoot P and K concentrations decreased. A possible explanation of this dilution response is that planting‐time P and K fertilizers, which were applied in a band near the seed furrow, may have enhanced the uptake of P and K in a manner that was independent of N‐fertilizer treatments. Increased shoot‐dry‐weight production due to the application of N fertilizers, if P and K uptake were similar across N‐fertilizer treatments, would lead to decreased shoot P and K concentrations in N‐sufficient compared with N‐deficient plants. Conversely, N‐fertilizer‐induced increases in shoot dry weight were accompanied by increased shoot concentrations of N, Ca, and Mn. This synergistic response between dry‐weight accumulation and shoot N concentration was present at all leaf developmental stages studied, while that for Ca was present only at VT. Thus, N fertilizer applications that increase shoot dry weight can affect the dilution and synergistic responses of specific mineral nutrients in maize shoots. Crop developmental stage as well as the location of these specific mineral nutrients in the soil profile might play important roles in mediating these responses.     

Integrated Use of Nitrogen Fertilizer and Fish Manure: Effects on the Growth and Chemical Composition of Spinach

ABSTRACT

Combinations of inorganic nitrogen and biological fertilizers are currently advised for integrated nutrient management. To prevent agricultural fish waste from polluting water sources, recycling of the organic waste of fish manure is advised. This study was conducted to determine effect of combinations of ammonium nitrate and fish manure on yield and spinach content under greenhouse conditions. Treatments consisted of fish manure (FM), ammonium nitrate (N) and the combination of fish manure and commercial fertilizer, with four doses of nitrogen (0, 100, 150 and 200 kg N ha^?1). Applications significantly affected leaf and root fresh and dry weights, nutrient element, antioxidant enzymes and the flavonoid content of spinach. Plant growth, chemical composition and yield were superior in treatments with 150–200 kg ha^?1 nitrogen doses with the combination of FM and N. FM application with N treatment provided maximum spinach yield and plant growth by reducing the use of commercial N fertilizer.     

不同有机肥对花生营养吸收、土壤酶活性及速效养分的影响

通过盆栽试验,研究等养分投入条件下,施用化肥与不同有机肥(猪粪、牛粪、鸡粪、麸酸有机无机复混肥)对花生营养吸收、土壤酶活性及速效养分的影响。结果表明,与化肥相比,施用有机肥脲酶活性提高6.2%～22.1%,磷酸酶活性提高7.9%～27.9%,过氧化氢酶活性提高45.1%～65.2%,分别以猪粪、鸡粪、麸酸有机无机复混肥最高,而转化酶活性各处理表现不一。施用有机肥较化肥促进了N、P、K养分向花生果仁转移累积,果仁吸N量、吸P量、吸K量、吸S量分别较化肥提高22.7%～78.0%、47.1%～74.5%、65.2%～91.6%、5.6%～61.2%,其NPK养分总吸收量以麸酸有机无机复混肥最高。施肥均提高了种植花生后的土壤N、P、K速效养分含量,施用麸酸有机无机复混肥还明显改善了土壤S素营养。     

Increased phosphorus availability from sewage sludge ashes to maize in a crop rotation with clover

A recycling of Phosphorus (P) from the human food chain is mandatory to secure the future P supply for food production. However, many available recycled P fertilizers from sewage sludge do not have an adequate P bioavailability and, thus, are not suitable for their application in soils with pH >5.5–6.0, unless being combined with efficient mobilization measures. The aim of the study was to test the P mobilization ability of red clover (Trifolium pratense L.) from two thermally recycled P fertilizers for a subsequently grown maize. Two sewage sludge ashes (SSA) were investigated in a pot experiment at soil pH 7.5 with red clover differing in its nitrogen (N) supply (added N fertilizer or biological N₂ fixation (BNF)), followed by maize (Zea maize L.). Shoot dry matter of maize was almost doubled when N supply of previous grown clover was covered by BNF, instead of receiving added N fertilizer. Similarly, shoot P removal of maize following clover with BNF was significantly increased. It is suggested that the P mobilization is related to the BNF, and a proton release of N₂ fixing clover roots led to the measured decrease in soil pH and thereby increased P availability of the tested fertilizers.     

Phosphorus availability of sewage sludge‐based fertilizers determined by the diffusive gradients in thin films (DGT) technique

The plant‐availability of phosphorus (P) in fertilizers and soil can strongly influence the yield of agricultural crops. However, there are no methods to efficiently and satisfactorily analyze the plant‐availability of P in sewage sludge‐based P fertilizers except by undertaking time‐consuming and complex pot or field experiments. We employed the diffusive gradients in thin films (DGT) technique to quantify the plant P availability of various types of P fertilizers with a novel focus on sewage sludge‐based P fertilizers. Mixtures of fertilizer and soil were incubated for 3 weeks at 60% water holding capacity. DGT devices were deployed at the beginning of the incubation and again after 1, 2, and 3 weeks. Two weeks of incubation were sufficient for the formation of plant‐available P in the fertilizer/soil mixtures. In a pot experiment, the DGT technique predicted maize (Zea mays L.) biomass yield and P uptake significantly more accurately than standard chemical extraction tests for P fertilizers (e.g ., water, citric acid, and neutral ammonium citrate). Therefore, the DGT technique can be recommended as a reliable and robust method to screen the performance of different types of sewage sludge‐based P fertilizers for maize cultivation minimizing the need for time‐consuming and costly pot or field experiments.     

Formulation of Environmentally Sound Waste Mixtures for Land Application

Major impediments to the land application of coal combustion byproducts (fly ash) for crop fertilization have been the presence of heavy metals and their relatively low and imbalanced essential nutrient concentration. Although nutrient deficiencies, in particular N, P, and K, may be readily augmented by adding organic wastes such as sewage sludge and animal manure, the indiscriminate application of mixtures to crops can cause excessive soil alkalinity, imbalanced nutrition (P, Mg), phytotoxicities (B, Mn, ammonia, nitrite), and unspecified contamination of the food chain by elements such as As. In this study, nutrient availability data and linear programming (LP) were used to solve these problems by formulating fly ash-biosolid triple mixtures which complied with both plant and soil fertilization requirements, and met existing U.S.A. environmental regulations for total As application in sewage sludge (EPA-503). Thirteen different fly ash samples were LP-formulated with sewage sludge, poultry manure, CaCO₃, and KCl to yield 13 unique mixtures, which were then evaluated in greenhouse pot experiments. Results indicated that normal growth and balanced nutrition of sorghum (Sorghumbicolor L.) and soybean (Glycine max (L.) Merr.) crops were achieved in all mixtures, comparable to a balanced fertilizer reference treatment, and significantly better than the untreated control. Phytotoxic levels of B, NH₃, NO₂ ^-, overliming problems, and excessive As levels which were previously encountered from indiscriminate use of these waste materials, were all well controlled by LP-formulated mixtures. Most fly ash quantities in mixtures were limited by either available B (< 4 kg ha^-1) or total As (< 2 kg ha^-1) restrictions during formulation, while the most alkaline fly ash was limited by its high calcium carbonate equivalence (CCE = 53.9%). These results confirmed that fly ash land application should not be at arbitrary fixed rates, but should be variable, depending on the soil, crop, and particularly the fly ash chemistry.     

The role of non‐crystalline Fe in the increase of SOC after long‐term organic manure application to the red soil of southern China

Because of the important role of soil organic carbon (SOC) in nutrient cycling and global climate changes, there has been an interest in understanding how different fertilizer practices affect the SOC preservation and promotion. The results from this study showed that long‐term application of manure (21 years) could increase significantly the content of SOC, total nitrogen (N) and soil pH in the red soil of southern China. The chemical structure of SOC was characterized by using solid‐state cross‐polarization magic angle spinning (CPMAS) ¹³C nuclear magnetic resonance (NMR) spectroscopy, and the aromatic C, ratio of alkyl C : O‐alkyl C, aromaticity and hydrophobicity of mineral fertilizers N, P and K plus organic manure (NPKM) and organic manure (M) treatments were less than those of mineral fertilizer nitrogen (N) and mineral fertilizers N, P and K (NPK) treatments. Both poorly crystalline (Fe_o) and organically complexed (Fe_p) iron contents were influenced significantly (P < 0.05) by different fertilizers, and it was observed that NPKM and M treatments increased the non‐crystalline Fe (Fe_o‐Fe_p) content. There was a significant (P < 0.01) positive correlation between soil organic C and non‐crystalline Fe in both the surface (0–20 cm) and subsurface (20–40 cm) soils. The results suggested that non‐crystalline Fe played an important role in the increase of SOC by long‐term application of organic manure (NPKM and M) in the red soil of southern China.     

Long‐term effects of animal manure and mineral fertilizers on phosphorus availability and silage maize growth

A better appraisal of the plant availability of soil phosphorus (P) added with animal manure is crucial to alleviate environmental impacts from over‐application of P. This study compares the availability of P to maize in the Askov long‐term experiments using unmanured plots and plots receiving corresponding rates of nitrogen (N), P and potassium (K) in mineral fertilizers or manure. Total‐P and water extractable P (Pw) in soil, and plant height, dry weight, P concentration and P uptake were determined in early August. Final yields were determined in late October. Soil Pw was similar for plots receiving corresponding rates of P in mineral fertilizer or manure form. With a strong relationship between Pw, and maize growth and final yields, Pw was a reliable indicator of P availability to maize. Plant dry weight, P concentration and P uptake in early August were 23%, 8% and 31% higher, respectively, for maize grown on soil receiving manure compared with mineral fertilizer, while final maize yield in late October was 13% higher. Plant height and dry weight determined in early August suggested that maize development at this growth stage defined final maize yield. We conclude that the availability of P was similar after long‐term application of corresponding rates of P in animal manure and mineral fertilizers, and that animal manure improves the growth of maize compared to mineral fertilizers. This is ascribed to micronutrients and residual N effects from previous additions of manure.     

Forms and solubility of plant nutrient elements in tropical plant waste biochars

Thailand is an agriculture‐based country which produces large amounts of agricultural waste. Making biochar from this waste can reduce pollution, decrease costs of production, and increase C sequestration. The agronomic benefits of biochar are partly derived from the available plant nutrients in biochar. This study investigated the fertilizer value of biochars manufactured by slow pyrolysis. Pyrolysis temperature and feedstock type affect nutrient concentrations and nutrient element speciation in biochar. The physio‐chemical, mineralogical and structural properties of biochars made from 14 agriculture wastes (soybean cake, corncob, lemon peel, sugar palm fibre, durian shell, tamarind wood, coconut fibre, coconut shell, bamboo wood, rice husk, eucalyptus wood, oil palm fruit, coffee waste, and bagasse) were investigated. The plant nutrients in biochar mostly occurred in crystalline minerals which were present on the surface and inside the cell structure of biochar. Most biochars examined in this research contained calcite (CaCO₃). The presence in biochars of several K‐minerals [archerite (KH₂PO₄), chlorocalcite (KCaCl₃), kalicinite (KHCO₃), pyrocoproite (K₂MgP₂O₇), struvite‐K (KMgPO₄ · 6 H₂O), and sylvite (KCl)] encourages the use of biochar as a K‐fertilizer. Fibre, fruit and wood biochars contained considerable amounts of K, Ca, and P. Sugar palm and coconut fibres also contained high level of Na in halite. This study recommends the utilization of biochars manufactured from sugar palm fibre, coconut fibre, durian shell, and oil palm fruit as fertilizers. With their appreciable contents of plant nutrients in highly to moderately soluble compounds these biochars should be effective fertilizers, especially for use by organic farmers who cannot use any chemical fertilizers.     

Using Commercially Available Ion‐Exchange Membranes to Monitor Plant‐Available Nutrients in Cranberry

Abstract

Monitoring in‐season nutrient availability in cranberry (Vaccinium macrocarpon Ait.) is hampered by tissue sampling being limited to a short, late‐summer period, and a low‐pH, high‐iron (Fe) soil environment limits soil‐test result interpretation. To evaluate monitoring available in‐season nitrogen (N), phosphorus (P), and potassium (K), commercially available ion‐exchange membranes (PRS?) were placed in plots where standard fertilizer practices were supplemented with the controlled‐release fertilizer (CRF) Osmocote? 14–14–14 at 0, 112, 224 or 336 kg/ha rates. PRS? nitrate (NO₃)‐N was related only to CRF fertilizer, whereas PRS? ammonium (NH₄)‐N reflected both the CRF and in‐season fertilizer applications. Large increases in PRS? NH₄‐N with increasing CRF rates suggested a synergistic effect of CRF on fertilizer NH₄‐N availability. PRS? P was positively correlated with CRF P but negatively to in‐season P applications, whereas PRS? K was related to in‐season fertilizer applications but not to CRF, suggesting poor plant P availability in the soil environment and relatively little K contribution from CRF, respectively. These results show promise for using PRS? in cranberry.     

Residual effects of poultry litter on silage maize (Zea mays L.) growth and soil properties derived from volcanic ash

Abstract

Poultry litter (PL) is a cheap alternative to conventional fertilizers. The use of PL in this way also reduces the environmental problems normally associated with its disposal. The residual effect of PL may reduce the amount of fertilizer (especially N fertilizer) required by subsequent crops. This study examines the residual effects of PL (with and without additional mineral fertilizer) on the properties of a volcanic ash soil and on silage maize (Zea mays) yields in central Chile. Poultry litter and mineral fertilizer were applied in 2002–2003 and their residual effects were determined in 2004–2006. The dry matter (DM) yield, nutrient balance and apparent nitrogen recovery efficiency (ANRE) of the silage maize were determined for each season, and the soil properties were analyzed at three depths (0–20, 20–40 and 40–60 cm) at the end of the third season. Crop yield showed a positive response to all fertilizer treatments. The residual effect, the nutrient balance, N uptake and ANRE also improved with fertilizer treatment, especially with the PL treatments. The average DM yield for the PL treatments was higher than that observed using mineral fertilizer by 2.8 and 1.2 Mg ha^?1 in the third and fourth years, respectively. The ANRE was generally higher in the PL treatments, although it decreased over time (12.4 and 1.7% for the last 2 years, respectively). The mean ANREs for the mineral fertilizer treatment were 4.1 and 1.6% for the same years. The results suggest that the PL treatments had an important positive residual effect in terms of N supply. This should be taken into account when planning the next crop. After two annual applications of PL, slight increases were observed in soil NO₃-N at a depth of 0–20 cm, and extractable P at depths of 20–40 cm and 40–60 cm. No other soil variables were significantly affected by any of the treatments. An additional source of K was found to be necessary to maintain an adequate soil K level.     

Codigested dairy slurry as a phosphorus and nitrogen source for Zea mays L. and Amaranthus cruentus L.

Residues from biogas production contain essential plant nutrients such as nitrogen (N), phosphorus (P), and potassium (K) but also organic matter, and should be recycled in crop production. For efficient re‐use as fertilizers, the availability of nutrients for crops and the effect of the residues on soil fertility need to be evaluated. Focusing on the element P, we compared effects of codigested slurry with dairy slurry, highly soluble mineral NPK fertilizer, and a control without any P supply (NK). Codigested slurry used in this experiment was based on anaerobic digestion of dairy slurry, maize silage, and wheat grain. The fertilizing effects were tested in an 8‐week pot experiment on a sandy and a loamy soil using two crop species (Zea mays L., Amaranthus cruentus L.). The plant P uptake was up to 64% greater in the slurry treatments than in the treatment without P. The effect of codigested slurry on P uptake was comparable to that of dairy slurry and mineral P. Plant N uptake from codigested slurry was lower than that from mineral N (NK, NPK), but tended to be higher than from dairy slurry. The water‐soluble and double lactate–soluble P content of the soil was lower in the slurry treatments than in the mineral‐P treatments and accompanied by higher contents of microbial‐bound P. Differences between both organic fertilizers were detected for dehydrogenase activity which was up to 32% lower in soils fertilized with codigested slurry than it was in soils fertilized with dairy slurry. Our results indicate that codigestion of slurries in biogas plants does not substantially alter their fertilizer value as P and N sources for crops.