Agronomic Effectiveness Research Articles

Nutritional status of rubber growing soils in the Moneragala district

Rubber cultivation is being expanded extensively into non traditional rubber growing areas such as Moneragala district in the intermediate zone of Sri Lanka. This study determines the nutritional status of these soils for the growth of rubber [Hevea brasiliensis (A. Juss.) Muell. Arg.] and the degree of nutrient variability. Soil samples were collected from the surface layers (0 - 0.3 m) and the availability of N, P, K, and Mg status and the urease activity were determined. Leaf N, P, K, and Mg status in samples collected from Kalutara, Kegalle and Moneragala regions, were also determined to compare the nutritional status of the plants among regions. Soils in the Moneragala region exhibited a very high variability with regard to exchangeable K (23 - 273 ppm) and exchangeable Mg (15 - 346 ppm) contents. The urease activity of the soils was very low (7 μg of NH₄⁺-N released g^-1hr^-1) compared to traditional rubber growing areas. This highlights the need to evaluate the agronomic effectiveness of urea as the N fertilizer in rubber growing soils in this region. Leaf N levels in the Moneragala region was significantly low but leaf Mg levels in all regions were in the high range. The fertilizer requirement of rubber plants could be highly site-specific in this region and therefore the currently used low K fertilizer mixture with a Mg source may not be equally effective in all parts of the region. <strong>Key words</strong>: intermediate zone; Moneragala; nutrients; rubber growing soils; urease activity DOI: 10.4038/jrrisl.v87i0.1811 <em>Journal of the Rubber Research Institute of Sri Lanka, </em>(2005) <strong>87</strong>, 23-35

Fertilizer Effectiveness of Phosphorus Recovered from Broiler Litter

Phosphorus can be recovered from broiler litter using a new process (“quick wash”). However, limited information is available on the beneficial use of this P product as plant fertilizer. The objective of this study was to determine the agronomic effectiveness of this P material. A greenhouse study was conducted with annual ryegrass (Lolium multiflorum Lam.) to compare the recovered phosphorus (RP) to both commercial triple superphosphate (TSP) and raw broiler litter (BL) as a P source. The study consisted of a 7‐wk experiment that was repeated three times. Fertilizer rates were 0, 22, 44, 88, and 176 mg P kg−1 soil. Three harvests of the ryegrass were made at 2‐wk intervals. On average, biomass production was higher than the control with no P for plants fertilized with RP, BL, or TSP. Total P uptake increased linearly with application rate for all three fertilizer materials. At the highest application rate, total P uptake was 36.1 mg pot−1 for TSP, 21.3 mg pot−1 for the BL, and 17.3 mg pot−1 for the RP. Chemical analysis of the RP material revealed that more than 90% of the total P in the RP material was mostly as citrate‐soluble. Mehlich‐3 extractable soil P at the end of the experiment indicated that less RP material dissolved than TSP during this short study. The RP material appears to have potential as a fertilizer.

Eficiência agronômica de compostos organominerais obtidos pelo processo humifert

A produção tradicional de fertilizantes fosfatados gera grandes volumes de rejeitos e entre estes estão materiais ricos em P, representando um bem mineral inutilizado. Para aproveitar esses rejeitos surgiu o processo Humifert, que tem como objetivo o tratamento ácido da mistura de minérios fosfáticos (elevado ou baixo teor de P) com material orgânico, incrementando a solubilidade do P contido no composto fertilizante, visando aumentar a eficiência agronômica (EA). Este trabalho objetivou avançar a pesquisa sobre o processo Humifert, com a realização de testes de funcionamento do equipamento e experimentos agronômicos, visando avaliar a EA dos compostos obtidos em relação à fonte tradicional de P. Foram realizados dois experimentos agronômicos, sendo um com fosfato monocálcico (FMC), rocha fosfática (RF) de Patos de Minas e turfa, submetidos ou não ao processo Humifert, e foi cultivado milho. O segundo experimento teve como fontes de P o FMC, fosfato reativo de Arad, rejeito de Tapira e turfa, submetidos ou não ao processo Humifert. As culturas utilizadas foram milho e braquiária (três cortes), para avaliar efeito residual das fontes. Em ambos os estudos, avaliou-se a matéria seca da parte aérea (MSPA) das plantas e os dados foram submetidos ao teste de médias. No primeiro experimento, o FMC proporcionou maior MSPA, e a mistura da rocha fosfática Pato de Minas com turfa submetida ao processo foi superior ao controle (sem aplicação de P). No segundo experimento, o FMC foi superior na primeira cultura (milho), e na média dos cultivos Arad foi equivalente ao FMC. Embora tenha havido algumas vantagens em termos de incremento de MSPA devido ao processo, a solubilidade e resultados agronômicos indicam a necessidade de mais pesquisas para adequar as reações e obter melhor qualidade das fontes de P.

Relative Agronomic Effectiveness of Phosphate Rock Compared With Triple Superphosphate for Initial Canola, Wheat, or Ryegrass, and Residual Wheat in Two Acid Soils

Direct application of phosphate rock (PR) may provide the essential phosphorus (P) nutrient for crop production in acid soils. However, the agronomic effectiveness of PR depends on several factors including PR reactivity, soil properties, and crop species. This greenhouse study investigated the effects of PR reactivity, soil pH, Al saturation, and crop species on the initial and residual relative agronomic effectiveness (RAE) of PR compared with water-soluble triple superphosphate (TSP) in two acid soils (Hartsells pH 4.8 and Hiwassee pH 5.4). Three PR sources, Tunisia, Mali, and Togo, representing high, medium, and low PR reactivity, respectively, were used. The soils were treated with P sources at 0, 25, 50, 100, 200, and 500 mg P kg−1 soil. Wheat, ryegrass, and canola were the test crops in the first season, and wheat was used as a residual crop after all three initial crops in the second season. Soil samples were collected for chemical analyses at 0 and 500 mg P kg−1 soil after the first crops. The initial RAE of PR for crop species followed: canola > ryegrass = wheat in the Hartsells soil and canola > ryegrass > wheat in the Hiwassee soil. However, the residual crop of wheat after wheat, wheat after ryegrass, and wheat after canola did not show any significant effect of previous crop. Among P sources, both initial and residual RAE followed: TSP > Tunisia PR > Mali PR ≥ Togo PR for all the crops and soils except for the initial canola crop grown in Hiwassee soil where all PR sources were as effective as TSP. In general, the RAE of PR in Hiwassee soil was higher than that of Hartsells because of the negative effects of soil acidity and Al saturation on crop growth in the Hartsells soil. A significant relationship between available P after first crops and residual wheat grain yield was found in the Hiwassee soil.

Chemical behavior of fluid and granular Mn and Zn fertilisers in alkaline soils

The grain yield benefits of applying micronutrient fluid fertilisers over conventional granular products in calcareous sandy loam soils have been agronomically demonstrated. An understanding of the fundamental mechanisms and reactions occurring following application of these products to soils is critical to improve fertiliser management. We therefore examined the diffusion, solubility, and potential availability of manganese (Mn) and zinc (Zn) from both granular and fluid forms of Mn and Zn fertiliser in an alkaline calcareous and alkaline non-calcareous soil using laboratory incubation experiments in conjunction with an isotopic dilution technique with 54Mn and 65Zn. Enhanced mobility, solubility, and/or potential availability of Mn and Zn from fluid fertilisers were observed in comparison to Mn or Zn from granular fertilisers in both soils after 5 weeks of incubation. Differential behaviour of fluid and granular fertilisers for Mn and Zn appeared to be independent of their effects on soil pH. Most (~90%) of the Mn in granular fertiliser dissolved and diffused out of the granule but was retained within 4 mm of the point of granular placement, whereas most (~85%) of the Zn in the granular Zn fertiliser source remained in the granule. Our data suggest that the superior agronomic effectiveness of fluid Mn and Zn fertilisers observed in calcareous soils under field conditions may have resulted from the enhanced diffusion (Mn) and/or solubility/availability (Mn, Zn) of these micronutrients in soil when applied in fluid form.

Genetic Variations of Brassica Cultivars for P Acquisition in a P Stress Environment and Comparison of P Sources for Sustainable Crop Management

To compare the growth performance of Brassica in a phosphorus (P) stress environment and response to added P, six Brassica cultivars were grown in pots for 49 days after sowing, using a soil low in P [sodium bicarbonate (NaHCO3)–extractable P = 3.97 mg kg−1, Mehlich III–extractable P = 6.13 mg kg−1] with (+P = 60 mg P kg−1 soil) or without P addition (0P). Phosphorus‐stress markedly reduced biomass accumulation and P uptake by roots and shoots. However, root–shoot ratio remained unaffected, implying that relative partitioning of biomass into roots and shoots had little role to play in shoot dry matter (SDM) production by cultivars. Biomass correlated significantly (P < 0.01) with total P uptake. Under P stress, the cultivars that produced greater root biomass were able to accumulate more total P content (r = 0.95**), which in turn was related positively to SDM and total biomass (r > 0.89**) and negatively to P‐stress factor (r = −0.91**). There was no correlation between P efficiency (PE) (relative shoot growth) and plant P, but PE showed a very significant correlation with shoot P content and SDM. Wide differences in growth and better performance of cultivars such as ‘Brown Raya’ and ‘Con‐1’ under P stress encouraged screening of more germplasm, especially in the field, to identify P‐tolerant cultivars. In another study, potential relative agronomic effectiveness (RAE) of sparingly soluble P sources was investigated by growing two contrasting cultivars. The P sources incorporated into soil at 0, 10, 25, 50, and 100 mg P Kg−1 were (i) powdered Jordan rock P (RP), (ii) triple superphosphate (TSP), (iii) powdered low‐grade TSP [TSP(PLG)], (iv) a mixture of RP + TSP compacted into pellets at 50:50 P ratio [RP + TSP(PelC)], and (v) a mixture of powdered RP + TSP at 50:50 P ratio [RP + TSP(PM)]. The RP was low in RAE and only 5 and 29% as effective as TSP in producing dry matter (DM) of P‐sensitive ‘B.S.A.’ and P‐tolerant ‘Brown Raya’ cultivars, respectively. There were no significant differences between TSP and RP + TSP(PelC) in DM yield of ‘Brown Raya,’ whereas, in the case of ‘B.S.A.’ RP + TSP(PM) was significantly less effective than RP + TSP(PelC) compared with TSP. Combined utilization of superior genome and P sources [such as TSP(PLG) and RP + TSP(PelC)] produced from low‐grade RP (that cannot be used either for direct application or acidulated P fertilizers) can be used as an alternative strategy for sustainable crop production, especially in resource‐poor environments. Further field trials at the level of cropping systems are needed.

EFFECTS OF COMBINING ORGANIC MATERIALS WITH INORGANIC PHOSPHORUS SOURCES ON MAIZE YIELD AND FINANCIAL BENEFITS IN WESTERN KENYA

SUMMARYDue to escalating costs of imported fertilizers, there is renewed interest in the use of local nutrient resources in managing soil fertility in Kenya. We tested the effect of two organic materials, farmyard manure (FYM) and Tithonia diversifolia (tithonia), and an inorganic N fertilizer, urea, when applied alone or in combination with three inorganic P sources, triple superphosphate (TSP), Minjingu phosphate rock (MPR) and Busumbu phosphate rock (BPR), on maize yields and financial benefits. The study was conducted for three consecutive seasons, from March 2007 to August 2008 in western Kenya. FYM and tithonia were applied to supply 20 kg P ha−1 in treatments where they were used either alone or in combination with the inorganic P sources while 40 kg P ha−1 was from the inorganic P sources in the combination. Where urea was used, the inorganic P sources were applied at 60 kg P ha−1. When applied in combination with urea, MPR was a better P source for maize than TSP or BPR. However, when applied in combination with FYM or tithonia, TSP was the best P source. Treatments including tithonia were more effective in increasing maize yields than those without it with a similar total P application rate. The agronomic effectiveness of tithonia did not, however, translate to economic attractiveness, mainly due to very high labour costs associated with its use. FYM when applied alone at 20 kg P ha−1 was the only treatment that exceeded a benefit:cost ratio of 2 and, therefore, the most likely, of the tested technologies to be adopted by farmers.

The Rule of Organic Fertilizer on Fertilizer Efficiency and Requirement Rate for Vegetable Crop on Inceptisols Ciherang, Bogor

Utilization of organic fertilizer is an alternative to increase soil health and supply a small amount of plant nutrient. Meanwhile agricultural soil in Indonesia commonly have low organic carbon content (&lt;2%) therefore application of organic fertilizer is recommended. Based on that, the aim of the research is to measure the effectiveness of organic fertilizer on caisim (Brassica chinensis L.) growth, to measure the release of N-NO3- and N-NH4+, to determine the recommendation of organic fertilizer for caisim on Incentisols Ciherang, Bogor. The research had been conducted at Research and Soil Testing Laboratory and green house of Soil Research Institute, Laladon – Bogor on April to July 2008 using soil sample of Inceptisols Ciherang, Bogor. The treatments were: Control (No fert.), NPK, rates of NPK + 500 kg organic fertilizer, 500 kg and 1000 kg organic fertilizer (No NPK), NPK+250 and 750 kg organic fertilizer. The five replications research had been conducted with Completely Randomized Design. The result indicated thats: (1) NPK fertilizer increased with addition of organic fertilizer approved by the evidence of increasing of plant high 2-10%, leaves number 1-2%, and crop production 16-36%. The relative agronomic effectiveness (RAE) of treatment NPK+various rate of organic fertilizer were higher than NPK alone with value of 136-181%. (2) The release of NH4+-N and NO3--N from anorganic fertilizer (NPK treatment) in four weeks incubation period showed balance proportion with N rate. Nitrogen released from organic fertilizer in the same incubation period are 5.39 mg NH4+-N kg-1 and 12.39 mg NO3- -N kg-1. (3) The best organic fertilizer rate based on fertilizer curve for Inceptisols Cicadas-Bogor having low C and N-organic is 560 kg organic fertilizer + NPK (300 kg Urea ha-1; 50 kg SP-36 ha-1; 50 kg KCl ha-1) produce caisim 134 g bag-1.

The effect of NPK Compound (6:16:7) on Chemical Soil Properties of Thapic Epiaquands and Cucumber Yield

The effect of NPK compound (6:16:7) on chemical soil properties of Thapic Epiaquands, growth and yield of cucumber (Cucumis sativus) has been studied in Punthuk Rejo Village, Karanganyar District. The aims were to study the influence of NPK fertiliser on chemical soil properties, growth and yield of cucumber. The treatments were arranged in Randomized Complete Block Design and replicated three times. The treatments were rate of NPK fertilisers including control, NPK standard, 150 kg NPK compound (6:16:7) ha-1, 300 kg NPK compound (6:16:7) ha-1, 450 kg NPK compound (6:16:7) ha-1, 600 kg NPK compound (6:16:7) ha-1, 300 kg NPK compound (6:16:7) ha-1 + ¼ NPK standard, and 300 kg NPK compound (6:16:7) ha-1 + ½ NPK standard. The NPK standard originated from single fertiliser, namely urea, SP-36 and KCl, while the NPK compound was Agrotop, containing 6.15% N, 16.23% P2O5 and 6.87% K2O following named NPK compound (6:16:7). The rate of NPK standard was 100 kg urea ha-1, 100 kg SP-36 ha-1 and 200 kg KCl ha-1 referring to the local recommended fertiliser rate. Application of NPK, both NPK (6:16:7) and NPK Standard, improved the chemical soil properties, namely N, P and K total as well available P. So far, application of 300 kg NPK compound ha-1 significantly increased the number of cucumber fruits and cucumber yield. Compared to the control, the increases were 13% and 44% for the number of cucumber fruits and cucumber yield, respectively. So far, combination of NPK compound (6:16:7) at the rate of 300 kg ha-1 with half recommended rate of NPK standard yielded a significant effect on both the number of cucumber fruits and weight of cucumber. These improvements were comparable to the NPK standard under fully recommended rate. The relative agronomic effectiveness value of combination of NPK (6:16:7) at the rate of 300 kg ha-1 with half recommended rate of NPK standard were about 100%, similar with the value of NPK standard. The economic analysis indicated that NPK standard with recommended application rate and combination of NPK Agrotop at the rate of 300 kg ha-1 with half recommended rate of NPK standard gave high benefit, B/C ratio and IBCR. The B/C ratio and IBCR were higher than one.

Relative efficiency of diammonium phosphate and mussoorie rock phosphate on productivity and phosphorus balance in a rice–rapeseed–mungbean cropping system

The field experiments were conducted at the Indian Agricultural Research Institute, New Delhi, India for 3 years from 2001–2002 to 2003–2004 to study the relative efficiency of diammonium phosphate (DAP) and Mussoorie rock phosphate along with phosphorus solubilizing bacteria inoculation (MRP + PSB) at different rates of application on productivity and phosphorus balance in a rice-rapeseed-mungbean cropping system. Phosphorus application significantly increased the productivity of rice-rapeseed-mungbean cropping system and resulted in an increase in 0.5 M NaHCO3 extractable P content in soil. The relative agronomic effectiveness (RAE) of MRP + PSB in relation to DAP as judged by the total productivity was 53–65% in the first cycle but reached 69–106% in the third cycle of the cropping system. The P balance (application—crop removal) was generally more positive for MRP + PSB than DAP and the highest P balance was recorded with an application of 52.5 kg P ha−1 as MRP + PSB, resulted in highest 0.5 M NaHCO3 extractable P content in soil. The present study, thus, shows that MRP + PSB could be usefully employed as an alternative to DAP in long term in the rice–rapeseed–mungbean cropping system.

Economizing the use of nitrogen fertilizer in wheat production through enriched compost

AbstractManipulation of organic wastes and their composts as a source of organic matter (OM) and nutrients is imperative for sustainable agriculture. Further, the fortification of composts with chemical fertilizer enhances agronomic effectiveness of both by reducing the amount of fertilizer and improving the quality of compost. The present study aimed to explore the potential of organic and chemical nutrient sources with their optimal application and integration for sustainable wheat production. Accordingly, waste fruits and vegetables were collected, dried, ground and processed in a composting vessel. During the enriched composting, waste material (300 kg) was fortified with 30 kg N, i.e. 25% of the standard rate (120 kg N ha−1) of N fertilizer. Treatments for both greenhouse and field experiments using wheat (Triticum aestivumL.) included: control (without any compost or N fertilizer), compost (non-enriched), fertilizer N 120 (120 kg N ha−1), nitrogen-enriched compost (NEC), NEC+N 30 (30 kg N ha−1) and NEC+N 60 (60 kg N ha−1). Application rate of composts (non-enriched or enriched) was 300 kg ha−1in the respective treatments. Phosphorus and potassium fertilizers were applied at 90 kg P2O5ha−1and 60 kg K2O ha−1, respectively in all treatments. The crop was grown to maturity, and data on wheat growth and yield attributes were recorded. Application of NEC significantly improved the growth, yield and N, P and K contents of wheat compared with compost and control treatments. The performance of NEC+N 60 was statistically similar to that of fertilizer N 120. Economic analysis also revealed the superiority of NEC+N 60 over other treatments in terms of net return and relative increase in income; however, the value/cost ratio was highest with NEC alone. For effective and economical use of N fertilizer, it is suggested to integrate N fertilizer at reduced rates with NEC. Through enriched compost, application rates can be decreased from tonnes to kilograms per hectare, and dependence on chemical fertilizer can be reduced to a certain extent. So the approach is farmer friendly as it lowers compost application rates, and is economically acceptable as it saves N fertilizer. It is also environmentally sustainable due the recycling of organic waste and possible reduction of N losses to the environment. Thus, the study has wide application in the global environment and fertilizer market.

Elemental analysis of phosphate rocks: For sustainable agriculture in Pakistan

The concentration of 32 elements was determined in phosphate rock samples from the Hazara phosphate deposits of Pakistan using instrumental neutron activation analysis (INAA) technique employing different irradiation protocols. These included 23 major, minor and trace elements (Al, As, Ba, Br, Co, Cr, Cs, Fe, Ga, Hf, K, Mn, Na, Rb, Sb, Sc, Sn, Ta, Th, U, V, Zn and Zr) and 9 rare earth elements (REEs) namely Ce, Eu, Ho, La, Lu, Nd, Sm, Tb and Yb. The results have been compared with the global values of these elements. The concentrations for most of the elements studied are lower than the concentrations reported in the literature whereas the concentrations of As, Co, Fe, K, Mn, Na and Sb are comparable. Two samples namely HR-4 and HR-5 have the highest concentrations for majority of the REFs with high enrichment factors. The quality assurance of data was performed through the concurrent use of Lake Sediment (SL-1) and GSJ-JR-1 (Rhyolite) reference materials. The acquired data will serve as a reference for the follow-up studies to assess the agronomic effectiveness of the Hazara phosphate rocks.

Characterization and Greenhouse Evaluation of Brazilian Calcined Nonapatite Phosphate Rocks for Rice

Little information is available on the agronomic effectiveness of calcined nonapatite phosphate rock (PR) sources containing crandallite minerals in the form of Ca–Fe–Al–P for flooded and upland rice (Oryza sativa L.). We conducted laboratory and greenhouse studies to (i) characterize the mineralogical composition, (ii) investigate the solubility and dissolution behavior, and (iii) evaluate the agronomic effectiveness of two nonapatite PR sources (Juquia and Sapucaia) from Brazil and compared them with (i) a highly reactive Gafsa PR (Tunisia) containing apatite in the form of Ca–P and (ii) a reference water‐soluble triple superphosphate (TSP) for flooded and upland rice. After calcination at 500°C for 4 h, the solubility of Juquia PR and Sapucaia PR in neutral ammonium citrate (NAC) significantly increased from almost nil to a maximum of 39.3 and 114 g P kg−1, respectively. X‐ray diffraction showed that crystalline crandallite mineral was transformed to an amophorus form after calcination. The solubility behavior of the two calcined PR sources followed the same trend as Gafsa PR, that is, P release decreased with increasing equilibrium pH in the 0.01 M KCl solution (pH 3.0–8.0). At pH 3, the solubility followed: Gafsa PR &gt; calcined Sapucaia PR &gt; calcined Juquia PR. No P release was detected from any of the PR sources at pH ≥ 5.0 in the solution, indicating the Ca–P characteristic of the Ca–Fe–Al–P mineral controlled P dissolution of the calcined PR. Without calcination, both Juquia PR and Sapucaia PR were totally ineffective for upland rice grown on a Hiwassee clay loam (fine, kaolinitic, thermic Rhodic Kanhapludult) with pH 5.4 whereas a significant P response was observed with the calcined PR samples. For flooded rice grown on Hiwassee soil, the calcined Juquia PR and Sapucaia PR were 66 and 72%, respectively, as effective as TSP in increasing rice grain yield whereas Gafsa PR was ineffective. For upland rice grown on the unlimed soil, Gafsa PR was as effective as TSP in increasing rice grain yield whereas calcined Juquia PR and Sapucaia PR were 89 and 83% of TSP. The effectiveness of Gafsa PR was reduced to 0% after the soil was limed to pH 7.0 whereas the two calcined PR sources were reduced to 49% of TSP. Soil available P extracted by iron oxide impregnated filter paper (Pi test) or anion‐exchange resin after rice harvest correlated well with P uptake by rice grain for flooded and upland rice.

Plant Availability of Phosphorus in Four Superphosphate Fertilizers Varying in Water‐Insoluble Phosphate Compounds

There is concern that the use of lower quality phosphate rock can result in elevated amounts of Fe–Al–P water‐insoluble compounds in fertilizers and, consequently, low agronomic effectiveness. Therefore, studies were conducted to evaluate the effect of some of these compounds on plant growth. Four commercial superphosphates varying in chemical composition (two single and two triple superphosphates) were selected for the study. Fertilizer impurities were collected as water‐insoluble residues by washing each P source with deionized water. A modal analysis, based primarily on elemental chemical analysis and x‐ray diffractometry, was used to estimate the chemical composition of each P source. Water‐soluble monocalcium phosphate (MCP) and the water‐leached fertilizer residues were prepared to give a range of fertilizers in terms of water‐soluble phosphorus (WSP) (0–100% of the available P as MCP). The water‐leached fractions, MCP, and the mixtures of MCP with water‐leached fractions were applied to supply 40 mg available P kg−1 to a thermic Rhodic Kanhapludult with pH values of 5.2 ± 0.05 (unlimed) and 6.4 ± 0.08 (limed). Wheat (Triticum aestivum L.) grown in a greenhouse for 101 d served as the test crop. The requirement for WSP was source and pH dependent. At a soil pH of 5.2, the fertilizers required 73 to 95% WSP to reach the maximum dry‐matter yield, while they required 60 to 86% WSP at pH 6.4. To reach 90% of the maximum yield, all superphosphate fertilizers required &lt;50% WSP. These results show that it is not always necessary to have high water solubility as required by legislation in many countries.

High‐Energy Milling Improves the Effectiveness of Silicate Rock Fertilizers: A Glasshouse Assessment

The effectiveness of intensively milled gneiss and potassium (K-feldspar) as K fertilizers was evaluated through a glasshouse experiment with ryegrass. Plant were grown on two soil types for 12 months. Results show that the agronomic effectiveness of milled gneiss was nearly as great as potassium sulfate (K2SO4), but milled K‐feldspar was much less effective because of the relatively small extent of dissolution of K‐feldspar in the soil. The positive effects of K‐silicate rock fertilizers (K‐SRFs) included increases in plant biomass, uptake of K and silicon (Si), and soil pH with increasing application rate of the K‐SRFs. The application of K‐SRFs will be most advantageous for amending K‐deficient soils, and high‐energy milling provides a simple method for manufacturing effective multinutrient SRFs.

Agronomic Evaluation of Calcined Crandallite from Three Brazilian Phosphate Deposits

Samples from the weathering mantle containing crandallite of three Brazilian phosphate deposits, Tapira, Catalão, and Juquiá, were characterized, calcined, and agronomically evaluated. The calcination process increased total phosphorus (P) and neutral ammonium citrate soluble (NAC) P contents of all samples. The NAC solubility of original Tapira, Catalão, and Juquiá was about 5% of total P, whereas for calcined samples it was 54, 16, and 53%, respectively. In a greenhouse study, rates of P were applied at 0, 10, 20, 40, 80, and 120 mg P kg−1 from the calcined materials and MCP (monocalcium phosphate) to an Ultisol cropped with upland and flooded rice for 65 days. The results showed that the calcined P samples increased dry‐matter yield and P uptake with increasing rates of P applied for both crops. Tapira and Juquiá were more effective for flooded than for upland rice. The calculated values of relative agronomic effectiveness of Tapira, Catalão, and Juquiá with respect to MCP were 57, 48, and 53% in dry‐matter yield for upland rice and 64, 50, and 69% for flooded rice, respectively.

Agronomic and Economic Potential of Tughutu and Minjingu Phosphate Rock as Alternative Phosphorus Sources for Bean Growers

On-farm experiments were conducted in farmers' fields at 6 different sites in Western Usambara Mountains (WUM) in northern Tanzania during the 2000-2001 cropping season. The objectives were to study the effects of Tughutu ( Vernonia subligera O. Hoffn) pruning in combination with Minjingu phosphate rock (MPR) or triple super phosphate (TSP) supply on the concentration of P in the tissues and seed yields of common bean, and to assess the economic returns of these different technologies to farmers. The experimental design was a randomized complete block with each of the 6 farmers' fields used as a replicate. The treatments included: control, MPR or TSP each at 26 kg P ha −1, Tughutu at 2.5 t ha −1, and Tughutu at 2.5 t ha −1 combined with MPR or TSP at 26 kg P ha −1. Addition of MPR or TSP alone significantly raised P concentration in bean shoots from 1.27 mg g −1 to 1.70 and 1.95 mg g −1 respectively. Combining MPR or TSP with Tughutu increased P concentration above the proposed deficiency level of 2 mg g −1. The relative agronomic effectiveness (RAE) of MPR ranged from 12.5% to 45.0%. Seed yields of common bean was markedly increased by 28%-104% from MPR or TSP supply alone, and 148%-219% from Tughutu application combined with 26 kg P ha −1 of MPR or TSP relative to the control. With Tughutu alone, seed yield increased by 53%. From economic analysis, the increase in seed yield with the supply of MPR or TSP combined with Tughutu translated into a significantly (P ≤ 0.001) higher marginal rate of return and dollar profit for common bean farmers in WUM in northern Tanzania. It is concluded that Tughutu and its combined application with MPR or TSP is an appropriate integrated nutrient management strategy that may increase bean yields and dollar profit to the rural poor communities in Tanzania.

Greenhouse Evaluation of Struvite and Sludges from Municipal Wastewater Treatment Works as Phosphorus Sources for Plants

Sewage sludge obtained by a conventional aerobic activated sludge process (CSS), P-rich sewage sludge from an enhanced biological P removal process (PRS), and struvite (MgNH 4PO 4 x 6H 2O) recovered from an anaerobic digester supernatant using a low-grade MgO byproduct from the calcination of natural magnesite as a Mg source (STR) were evaluated as P sources for plant growth. For this purpose, a greenhouse pot experiment was conducted using a P-deficient loamy sand soil and perennial ryegrass ( Lolium perenne L.) as the test crop. The P sources were applied at rates equivalent to 0, 9, 17, 26, 34, and 44 mg/kg P. Single superphosphate (SUP) was used as reference for comparison with the other P sources. The results obtained indicated that STR was as effective as SUP in increasing the dry matter yield and supplying P to ryegrass. Compared to SUP and STR, PRS and especially CSS exhibited less agronomic effectiveness as P sources, which may be attributed, at least partially, to greater soil P fixation because of the larger amount of Fe incorporated with these materials.

Agronomic Effectiveness of Calcium Phosphate Recovered from Liquid Swine Manure

A new manure treatment technology developed as an alternative to anaerobic lagoons on swine (Sus scrofa domesticus) farms includes solid‐liquid separation and subsequent recovery of soluble P as calcium phosphate from the wastewater. The objective was to determine the agronomic effectiveness of this calcium phosphate material. A greenhouse study was conducted with annual ryegrass (Lolium multiflorum Lam.). Three fertilizer materials were evaluated: the recovered P in two particle sizes (0.5–1.0 and 2.0–4.0 mm), and commercial triple superphosphate (TSP). Fertilizer rates were 0, 22, 44, 88, and 176 mg P kg−1 soil. Three harvests of the ryegrass were made at 2‐wk intervals. Total P uptake increased linearly with application rate for all three fertilizer materials. At the highest application rate, total P uptake was 37.8 mg pot−1 for TSP, 26.2 mg pot−1 for the recovered P with small particle size, and 9.0 mg pot−1 for the recovered P with large particle size. Chemical analysis of the recovered P material revealed that over 99% of the P2O5 in the recovered calcium phosphate was plant available P, mostly as citrate‐soluble. Mehlich‐3 extractable soil P at the end of the experiment indicated that little of the large particle size of recovered P material dissolved and became available during this short 10‐wk study. The recovered calcium phosphate appears to have potential as a fertilizer source.

Thermal treatment of aluminous phosphates of the crandallite group and its effect on phosphorus solubility

Optimization in the use of phosphate rocks is important and the residues of fertilizer production in the form of crandallite may be suitable for agronomic use after calcination. With the objective of evaluating the effect of thermal treatment of the aluminous phosphates of the crandallite group as related to solubility, crystalline structure and morphology, samples from the mine residues of three Brazilian phosphate deposits (Tapira-MG, Catalão-GO, and Juquiá-SP) were collected, air-dried, and screened to 100 mesh. Sub samples were thermally treated at 300, 500, 700, and 900°C for 2 hours. Treated and untreated materials were analyzed by X-ray diffraction, scanning electronic microscopy, energy dispersive X-ray spectrometry, and for the total and soluble P contents. The treatment of samples: (i) raised P solubility in neutral ammonium citrate solution, (ii) caused the disorganization of the crystalline structure of crandallite at 500°C and above, and (iii) altered their morphology (cracking and rounding). The increase in P solubility of samples after calcination indicates that the agronomic utilization of these marginal P sources may be of interest since plant growth may be favored due to higher P availability. New studies to evaluate these materials in order to determine their agronomic effectiveness must be carried out to establish adequate conditions that favor their use by plants.