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1.
Abstract

Phosphorus and sulfur deficiencies have been observed on many of the volcanic ash derived soils in Central America. One exploratory experiment was initiated in 1987 to examine maize (Zea mays L.) grain yield response to phosphorus, sulfur and nitrogen applied together on a volcanic ash derived soil in the Pacific coastal plain of Guatemala. Four cycles of yield data were collected in 2 rainy and 2 dry seasons. Treatments consisted of rate combinations of N (0, 100 kg ha‐1 as urea), P (0, 22 kg ha‐1 as triple superphosphate) and S (0, 57 and 114 kg ha‐1 as CaSO4.2H2O) applied together in continuous bands in a randomized complete block design. Residual P and S response was measured during the last two cycles, whereby only urea was applied at a constant rate to all plots. The combined analysis of the first two cycles demonstrated a linear response of yield to applied S when no P was applied (4.95, 5.75 and 5.95 Mg ha‐1 at 0, 57 and 114 kg S ha‐1 respectively), while yield response was quadratic when S as CaSO42H2O and P as triple superphosphate were applied together in a continuous band at 100 kg N ha‐1 (5.38, 6.38 and 5.48 Mg ha‐1 at the same S rates respectively). Response of yield to S was linear without and with P for the combined residual analysis of the last two cycles at the same N rate (4.65, 4.94, 5.26 and 4.68, 5.53, 5.56 Mg ha‐1 respectively). Grain yields were maximized over the four cycle period using a joint N, P, S band (100 kg of N as urea, 22 kg P as triple superphosphate, and 57 kg S as CaSO4.2H2O ha‐1). It is hypothesized that precipitation of dicalcium phosphate dihydrate (DCPD) and dicalcium phosphate (DCP) took place within the joint N‐P‐S band subsequently reducing the amount of P fixed as Fe or Al hydroxides and/or amounts of P complexed with amorphous allophane. The precipitation and subsequent dissolution of DCPD and DCP within the band could have increased P availability with time. Alternatively, SO4 = blocking of adsorption sites could have increased P availability by reducing the amount of P fixed by the soil. It is possible that both of the previously mentioned mechanisms played a role in first cycle yield responses since increases were noted at the low S rate (57 kg S ha‐1), while reductions were found when the S rate was doubled (114 kg S ha‐1). Significant residual response for the last two cycles was observed for the joint triple superphosphate, CaSO4.2H2O, urea band, especially at the high S rate. This suggests that excess precipitation of DCP and DCPD could have occurred and that this provided delayed dissolution of the precipitated P reaction products. Chemical characterization of precipitated reaction products within the band is needed as well as further verification on similar soils in order to validate the observed response.  相似文献   

2.
Soil fertility is declining in most agro‐ecosystems in sub‐Saharan Africa, and incorporation of forage legumes into production systems to utilize the nitrogen fixed by the legumes could alleviate the problem, if efficient nitrogen‐fixing legumes are used. The amounts of nitrogen fixed by Lablab, Medicago, Trifolium, and Vicia species and their contribution to the following wheat crop were estimated in field experiments on an Alfisol at Debre Zeit in the Ethiopian highlands. The amounts of nitrogen (N) fixed ranged from 40 kg N ha‐1 for T. steudneri to 215 kg N ha‐1 for L. purpureus. The increase in grain yields of wheat following the legumes ranged from 16% for T. steudneri to 71% for M. tranculata where no N fertilizer was applied to the wheat. Additional N fertilizer applied to wheat at 60 kg N ha‐1 had no significant effects on wheat grain or straw DM andN yields. In another experiment, eight lablab treatments consisting of factorial combinations of two cultivars (Rongai and Highworth), two Rhizobium inoculation treatments (inoculated and uninoculated) and two times of harvest (for hay at 50% flowering and for seed at seed maturity), were compared on lablab forage production and N yield, and residual effects on two succeeding wheat crops. Inoculation had no significant effects on nodulation, shoot DM or N yields. Rongai had significantly higher shoot DM and N yields than Highworth. Lablab harvested at flowering had significantly higher shoot DM and N yields than lablab harvested at seed maturity. Grain yields of the first wheat crop following the various lablab crops were 93–125% higher than grain yields of the wheat following wheat (continuous wheat) where no N fertilizer was applied. Therefore, lablab is a potential forage crop for incorporation into cereal production systems to improve feed quality and to reduce dependence on N fertilizers for cereal production.  相似文献   

3.
Conservation tillage systems, including ridge‐tillage, have become increasing popular with producers in the central Great Plains because of their effectiveness in controlling soil erosion and conserving water. A major disadvantage of the ridge system is that nutrient placement options are limited by lack of any primary tillage options. The objective of this research was to investigate the effects of method of phosphorus (P) placement and rate on irrigated grain sorghum [Sorghum bicolor (L.) Moench] grown in a ridge‐tillage system on a soil low in available P. This experiment was conducted from 1993 to 1995 on a producer's field near the North Central Kansas Experiment Field at Scandia, Kansas on a Carr sandy loam soil (course, loamy, mixed, calcareous, mesic, Typic Udifuvents). Treatments consisted of fertilizer application methods, surface broadcast, single band starter (5 cm to the side and 5 cm below seed), dual band starter (one band on each side of the row), and knifed in the center of the row middle (38 cm from each adjacent row). Each of these treatments was made at either 22 or 44 kg P2O5 ha‐1, and nitrogen (N) also was included at the rate of 13 kg ha‐1. Additional treatments were, a combination of 13 kg N and 44 kg P2O5 ha‐1 applied half broadcast and half as a single band starter, a 1:1 N:P2O5 ratio (44 kg N and 44 kg P2O5 ha‐1) applied as a single band starter, and a 3:1 ratio (134 kg N and 44 kg P2O5 ha‐1) applied as a single band starter. A no‐P check plot also was included. Broadcast and center‐of‐row middle knife applications were made approximately 1 week before planting. After planting, N was balanced on all plots to give a total of 180 kg ha‐1. Applied P treatments improved grain yield and nutrient uptake and consistently shortened the time from emergence to mid‐bloom in all 3 years of the experiment. On this low soil test P soil, treatments that subsurface banded P increased grain yield by 1.27 Mg ha‐1 compared to broadcast treatments. Placing N and P in a single starter band 5 cm to the side and 5 cm below the seed was as effective as placing a band on each side of the row. Knife applying N and P in the center of the row was not as effective as placement beside the row. Single band starter application of N and P in a 1:1 and or 3:1 N:P2O5 ratio consistently increased yields and nutrient uptake and shortened the time to mid‐bloom as compared to the single band starter treatment that provided only 13 kg N ha‐1. Over the 3 years of the study, these 1:1 and 3:1 N:P2O5 ratio starters were clearly superior to an other treatments.  相似文献   

4.
Organic agricultural systems rely on organic amendments to achieve crop fertility requirements, and weed control must be achieved without synthetic herbicides. Our objective was to determine the crop yield and soil quality as affected by a transition from grass to dryland organic agriculture in the Central Great Plains of North America. This study evaluated three beef feedlot compost(BFC)treatments in 2010–2015 following biennial application rates: 0(control), 22.9, and 108.7 t ha~(-1) on two dryland organic cropping systems: a wheat(Triticum aestivum)-fallow(WF) rotation harvested for grain and a triticale(Triticosecale)/pea(Pisum sativum)-fallow(T/P-F) rotation harvested for forage. The triticale + pea biomass responded positively to the 108.7-t ha~(-1) BFC treatment,but not the 22.9-t ha~(-1) BFC treatment. The wheat biomass was not affected by BFC addition, but biomass N content increased.Beef feedlot compost input did not increase wheat grain yields, but had a positive effect on wheat grain Zn content. Soil total C and N contents increased with the rate of 108.7 t ha~(-1) BFC after three applications, but not with 22.9 t ha~(-1) BFC. Soil enzyme activities associated with N and C cycling responded positively to the 108.7-t ha~(-1) BFC treatment. Saturated salts were high in the soil receiving 108.7 t ha~(-1) of BFC, but did not affect crop yields. These results showed that BFC was effective in enhancing forage yields, wheat grain quality, and soil C and N, as well as specific microbial enzymes important for nutrient cycling. However, the large rates of BFC necessary to elicit these positive responses did not increase grain yields, and resulted in an excessive buildup of soil P.  相似文献   

5.
Abstract

Fertilizer placement for corn (Zea mays L.) has been a major concern for no‐tillage production systems. This 3‐yr study (1994 to 1996) evaluated fertilizer phosphorus (P) or potassium (K) rates and placement for no‐tillage corn on farmers’ fields. There were two sites for each experiment involving fertilizer P or K. Treatments consisted ofthe following fertilizer rates: 0,19,and 39 kg P ha‐1 or 0, 51, and 102 kg K ha‐I. The fertilizer was broadcast or added as a subsurface band 5 cm beside and 5 cm below the seed at planting. Early plant growth, nutrient concentrations, and grain yields were measured. At the initiation of the study, soil test levels for P and K at the 0–1 5 cm depths ranged from optimum (medium) to very high across sites. Effects of added fertilizer and placement on early plant growth and nutrient concentrations were inconsistent. Added fertilizer had a significant effect on grain yields in two of twelve site‐years. Therefore, on no‐tillage soils with high fertility, nutrient addition, and placement affected early plant growth and nutrient utilization, but had limited effect on grain yield. Consequently, crop responses to the additions of single element P or K fertilizers under no‐tillage practices and high testing soils may not result in grain yield advantages for corn producers in the Northern cornbelt regardless of placement method.  相似文献   

6.
Abstract. In the Sahel, promising technologies for agricultural intensification include millet stover mulching and ridging. A four year on‐farm experiment was set‐up in order to assess the effect of various combinations of these two technologies on crop development and yield in a millet (Pennisetum glaucum (L.) R. Br.) ‐ cowpea (Vigna unguiculata (L.) Walp.) intercropping system. Treatments included bare surface, ridging, a surface applied banded millet stover mulch (2 t ha–1) and a banded millet stover mulch (2 t ha–1) buried in ridges. The latter three treatments were implemented exclusively in the cowpea rows, with an annual rotation between the millet and cowpea rows. On bare and ridged plots, millet yields fell below 100 kg grain ha–1 after the first year. This was ascribed mainly to soil acidification and loss of soil organic matter rather than to soil physical constraints or water availability despite extensive surface crusting and high soil penetration resistance and bulk density. Compared to the bare plots, ridging increased cowpea hay production by 330% over the four years which was attributed to lower soil penetration resistance and bulk density but also to a reduction of 0.15 cmol+ kg–1 exchangeable acidity in the ridges. Except during the severe drought year of 1997, millet grain yield in the banded mulch treatment remained fairly stable over time at 526 ± 9 kg ha–1. However, a detailed analysis revealed yield compensation mechanisms between various yield components depending on the timing of occurrence of the abiotic stresses. Cowpea productivity was always higher in buried banded mulch plots than in surface applied banded mulch plots but the former treatment appeared unable to sustain millet yields. This decline was attributed to a greater nutrient uptake by cowpea and more rapid acidification in the buried mulch treatment compared to the banded mulch treatment.  相似文献   

7.
In this study, efficacies of mined gypsum and phosphogypsum (PG), when applied at equivalent doses, were compared for sodic soil reclamation and productivity of rice–wheat system. Application of PG, followed by karnal grass as first crop, resulted in the greatest reduction of soil pH and exchangeable sodium percentage (ESP) followed by PG applied at 10 Mg ha?1 alone. Application of PG at 10 Mg ha?1 resulted in greater yields of both rice and wheat than other treatments. Ditheylenetriaminepentaacetic acid (DTPA)–extractable micronutrients of PG-treated soil were greater than in mined gypsum–treated soil. A greater portion of applied P entered the calcium (Ca)–phosphorus (P) fraction in PG-treated soil, which also resulted in more soluble P than the mined gypsum–treated soil. Phosphogypsum effected greater increase in aggregation, soil organic carbon, microbial biomass carbon, and aggregate associated carbon and decrease in zeta potential, leading to increased hydraulic conductivity and moisture retention capacity in soil over mined gypsum–treated soil.  相似文献   

8.
Abstract

In the Southwest of Buenos Aires Province (Argentina), wheat yields are limited by phosphorus (P) deficiencies in at least 50% of the area. The objective of this paper was to report on the relative efficiency of two different methods of application of ? fertilizer: (i) by row placement with the seed at sowing (RP) and (ii) by broadcasting and incorporation into the surface soil (BP). The design of the experiments was of complete blocks with a strip subplot. Treatments were ? rates and method of application. Subtreatments were ? fertilization at different times and rates. ? fertilizer was triple superphosphate (TSP). One experiment included diammonium phosphate (DAP). Yield response to ? was significant in 3 of the 4 experiments. The RP produced higher yields in three experiments, but differences were significant in only one site. The RP effects on yield are shown by comparison of yields for individual treatment rates and by the calculation of fertilizer efficiency, efficiency ratio and substitution rate (S), which is defined as the ratio of RP and BP rates rendering the same yield response. Of these, the substitution rate showed the most highly significant effects. Fertilizer efficiency for TSP broadcast ranged from 8 to 44 kg wheat kg‐1 P. Efficiency ratio of RP to BP for a rate of 16 kg ? ha‐1 was between 1.27 and 1.74. The S was significant in two experiments carried out on sandy loams where values of 0.31 and 0.39 were found for soils with 6 and 10 mg ? kg‐1 (Bray I). In general, RP improved wheat quality as determined by kernel and volume weight and also the ability of the crop to compete with weeds (Avena fatua).  相似文献   

9.
Two popular concepts of soil fertilization, basic cation saturation ratio (BCSR) and sufficiency level of available nutrients (SLAN), were tested on a calcareous soil (Aeric haplaquept) during 1995–1996 at the Bangladesh Rice Research Institute (BRRI) Regional Station Rajshahi using wheat as a test crop. According to BCSR concept the soil was deficient in potassium (K) and according to SLAN concept it was deficient in phosphorus (P), respectively. Potassium dose of 120 kg ha‐1 [to attain 2% saturation of total cation exchange capacity (CEC) according to BCSR] along with other two doses (0 and 60 kg K ha‐1) and P dose of 50 kg ha‐1 (to attain available P at sufficiency level) along with other two doses (0 and 100 kg P ha‐1) were compared in a randomized complete block design. The application of 50 kg P ha‐1 significantly increased plant height, spikes m2, grains per spike, grain and straw yields of wheat over 0 kg P ha‐1 with or without K but increasing P dose from 50 to 100 kg P ha1 did not give additional yields. The agronomic parameters and yields were not affected significantly by K application. Similar results were also observed in nutrient content and nutrient uptake. Thus, SLAN concept appeared as an effective tool for fertilizer recommendation for the calcareous soil while BCSR gave no apparent result there.  相似文献   

10.
Abstract

Mungbean [Vigna radiata (L). Wilczek] grown in rainfed calcareous soils suffers with phosphorus (P) deficiency. In view of high cost and low use efficiency of P fertilizer, greenhouse, incubation, and field experiments were carried out for determining P deficiency diagnostic criteria and efficient method of P fertilizer application in mungbean. In a pot culture experiment using a P‐deficient Typic Ustocherpt, maximum increase in grain yield with P was 686% over the control; and fertilizer requirement for near‐maximum (95%) grain yield was 30 mg P kg‐1 soil where fertilizer was mixed with the whole soil volume (broadcast) and 14 mg P kg‐1 where mixed with 1/4th soil volume (band placement). In a field experiment on a P‐deficient Typic Camborthid, however, maximum increase in grain yield was 262% over the control. Band placement resulted in 73% fertilizer saving as P requirement was 66 kg ha‐1 by broadcast and only 18 kg ha‐1 by band placement. Critical P concentration range appears to be 0.27–0.33% in young whole shoots (≤30 cm tall) and 0.25–0.30% in recently matured leaves. In an incubation study using the same Typic Ustochrept, P extracted by the sodium bicarbonate (NaHCO3), the ammonium bicarbonate‐diethlylenetriaminepentaacetic acid (AB)‐DTPA), and the Mehlich 3 soil tests correlated closely with each other, P concentration of whole shoots, and total P uptake by mungbean plants. Critical soil test P levels for pot grown mungbean were NaHCO3,9 mg kg‐1; AB‐DTPA, 7 mg kg‐1; and Mehlich 3, 23 mg dm‐3 soil. The more efficient and economical ‘universal’ soil test, AB‐DTPA, is recommended for P fertility evaluation of calcareous soils.  相似文献   

11.
Abstract

A greenhouse study was conducted to determine the effects of low‐rate commercial humic acid (HA) on phosphorus (P), iron (Fe), and zinc (Zn) availability and spring wheat yields, in both a calcareous soil and a noncalcareous soil. In Phase I, soluble P concentrations were monitored at 1.9, 3.8, and 5.7 cm from a monoammonium phosphate (MAP) fertilizer band that had either been coated with one of two HA products at the equivalent of 1.7 kg HA ha?1, a label rate, or left uncoated. Sampling occurred periodically up to 48 d after fertilizer application. In Phase II, uptake of P, Fe, and Zn and grain yield were measured in soils that had been fertilized with 7.5 or 25 kg P ha?1, either coated with HA or left uncoated. In Phase I, only three significant differences (P=0.05) out of 66 comparisons were found in soluble P concentrations between HA and control treatments at time points ranging from 4 to 48 d after fertilization. In addition, no significant differences were found in nutrient uptake, shoot biomass, or grain yield between HA and control treatments. These greenhouse results suggest that low commercial HA rates (～1.7 kg HA ha?1) may be insufficient to enhance spring wheat growth.  相似文献   

12.
Thirty field experiments on a range of soils in different rainfall zones of South Western Australia were used to examine the effectiveness, relative to freshly applied zinc (Zn) fertilizer of previously applied Zn fertilizer for grain yield of wheat. The soils had been fertilized with Zn at 0.2 to 1.2 kg Zn ha‐1, 9 to 24 years previous. The effect of applied nitrogen (N) fertilizer on grain yield and Zn concentrations in the youngest emerged blade (YEB) was also examined. At all sites, the current application of Zn fertilizer to soils previously treated with Zn did not increase grain yield. The highest level of N fertilizer did not reduce grain yield where Zn had been applied previously or induce Zn deficiency in wheat plants. The lowest level of Zn (0.2 kg Zn ha‐1, Experiment 17) applied 15 years earlier was still fully effective for maximum grain production. The application of currently applied Zn increased the Zn concentration in the YEB for 23 experiments. Application of N decreased Zn concentration in YEB in the 19 experiments, had no effect on the Zn concentration in 11 experiments, and increased Zn concentrations in two experiments. This was so for recent and previously applied Zn. In experiments where N decreased the Zn concentration in YEB, the concentration declined to 10 mg kg‐1 in seven experiments. Zn concentration in the grain was increased by the current application of Zn in 25 experiments. It had no effect in five experiments (Experiments 11–13, 21–22). The application of N fertilizer decreased the Zn concentration of the grain for both previously and currently applied Zn in 20 experiments. Nitrogen decreased the concentration of Zn in the grain to 10 mg Zn kg‐1 in seven experiments. Zinc extracted from the soil by DTPA was correlated with the amount of previously applied Zn fertilizer. DTPA‐extractable Zn for the experimental sites were 0.3 mg kg‐1, except for 2 experiments which were 0.2 mg/kg. The results show that where Zn fertilizer had been applied previously, applications of high levels of N fertilizer to cereal crops did not require further applications of Zn if superphosphate (400–600 mg Zn kg‐1) was used in the cropping and pasture phase. This is because of contaminates of Zn in rock phosphate used to make superphosphate. However, the requirements for Zn for wheat grain need to be reconsidered if diammonium phosphate (DAP) is used for cropping and if superphosphate applications are less than 150 kg ha‐1 during the legume crop or pasture species in rotation with the cereal.  相似文献   

13.
To examine the effect of zinc (Zn) application method on the utilization of phosphorus (P) from applied P fertilizer, a field experiment was conducted on basmati rice–wheat rotation with combinations of Zn levels (0, soil application of 2.5 kg Zn ha – 1 and two foliar applications of 2.0 kg Zn ha –1) and P levels (0, soil application of 8.7, 17.5 and 26.2 kg P ha –1). The highest pooled grain yields of basmati rice and wheat were obtained with soil application of 17.5 kg P ha –1 and foliar applications of 2 kg Zn ha –1. Foliar applications of Zn increased the P concentration in grain and straw and the total P uptake by basmati rice and the P concentration in flag leaves of wheat significantly, while soil or foliar application of Zn increased the total P uptake of wheat. Phosphorus application increased the Zn concentration in flag leaves, grain and straw of basmati rice and in grain and straw of wheat and the total Zn uptake of both crops. Phosphorus levels up to 17.5 kg P ha –1 increased utilization efficiency of soil or foliar application of Zn. Zinc application increased the P utilization efficiency of basmati rice and wheat up to 17.5 kg P ha –1 level; foliar Zn application was more effective in a wheat crop than a rice crop.  相似文献   

14.
Field experiments were conducted at the Indian Agricultural Research Institute, New Delhi, India for three years from 2001–2002 to 2003–2004 to study the relative efficiency of diammonium phosphate (DAP) and mussoorie rock phosphate (MRP) in a rice-potato-mungbean cropping system. Phosphorus application significantly increased productivity, protein yield and energy output of rice-potato-mungbean cropping system and resulted in an increase in 0.5 M sodium bicarbonate (NaHCO3) extractable phosphorus (P) content in soil. The MRP at 35 kg P ha?1 was at par with 17.5 kg P ha?1 as DAP in terms of productivity, protein yield, and energy output but significantly superior in terms of PSB population in soil. Phosphorus balance (application – crop removal) was generally more positive for MRP than DAP and the highest with an application of 52.5 kg P ha?1 as MRP. Present study indicates that P requirement of a rice-potato-mungbean cropping system can be met with 76–79% higher dose of MRP as compared to DAP.  相似文献   

15.
ABSTRACT

Nutrient uptake and grain and straw yield of Egyptian winter wheat (Triticum aestivum L. Merr.) were evaluated for two site-years after the seed inoculation with two biofertilizer products, Phosphorien, containing the phosphorus (P)-solubilizing bacteria Bacillus megatherium, and Nitrobien, containing a combination of nitrogen (N)-fixing bacteria Azotobacter chroococcum and Azospirillum liposerum. Ammonium nitrate and polymer-coated urea fertilizers were applied to plots alone and together with the biofertilizers at rates of either 83 kg N ha?1 or 186 kg N ha?1 for comparison. The highest grain yield (5.76–6.74 Mg ha?1) and straw yield (11.49–13.32 Mg ha?1) occurred at the highest fertilizer rates with N fertilizer. There was a slight additional increase in grain and straw yields when a biofertilizer was applied along with N fertilizer. A slightly higher grain and straw yield was measured with the polymer-coated urea treatment than with the ammonium nitrate treatment. The biofertilizer materials were not as effective as N fertilizers in producing grain (4.02–4.09 Mg ha?1) or straw (7.71–8.11 Mg ha?1) for either year, although the Nitrobien + Phosphorien combination increased these parameters over the N-fertilizer control. The effect of the Nitrobien biofertilizer in increasing grain yields was equivalent to a urea application rate of about 13 kg N ha?1. Biofertilizer inoculations increased iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) concentrations in wheat tissue (at boot stage), but these higher levels did not influence grain or straw yield.  相似文献   

16.
Abstract

Although manganese (Mn) deficiency in soybeans (Glycine max) has been recognized on the Atlantic Coastal Plain, it has not been well recognized in corn (Zea mays) until recent years. Hence, there is a lack of information relating to the diagnosis and correction of Mn deficiency in corn. Field experiments were conducted to determine if the Mn soil test interpretation for soybeans would work for corn. The leaf Mn critical level also was evaluated, as were soil and foliar application methods of correcting a deficiency. Corn yield response to Mn fertilization was best explained by both soil pH and Mehlich‐3 extractable Mn concentration. The influence of these two soil properties for predicting yield response was similar for corn and soybeans, but it appears that the soil Mn critical level is lower for corn than for soybeans. The critical Mn concentration in the ear leaf at early silking was found to be 11 mg kg‐1. Manganese banded with diammonium phosphate (DAP) was three times as effective as Mn broadcast with DAP in increasing the leaf Mn concentration of corn. Banding DAP also tends to increase the availability of native soil Mn. A foliar Mn rate of 0.6 kg ha‐1 applied once partially corrected a Mn deficiency, but multiple applications were required for optimum yield.  相似文献   

17.
The rice–wheat cropping system (RWCS), producing about 5–10 Mg ha–1 y–1 of grain, is the backbone of food‐crop production in South‐East Asia. However, this system shows signs of fatigue as indicated by declining yields, negative nitrogen (N) balances, and reduced responses to applied fertilizer at some research centers. The return of rice and wheat residues can recycle up to 20%–30% of the N absorbed by the crops. However, their wide C : N ratio can temporarily immobilize native and applied N. To overcome this immobilization, wheat‐straw application was supplemented with the incorporation of Sesbania green manure and mungbean residues, and their effects on productivity, agronomic N efficiency, and system's apparent N balances were studied. Combining the application of wheat straw with Sesbania green manure or mungbean residues increased cereal grain yield and agronomic N efficiency and improved the generally negative apparent N balances. The combined use of wheat straw and mungbean produced an additional 0.5–0.6 t ha–1 protein‐rich grain and thus appears to be the most promising residue‐management option for rice–wheat cropping systems in South Asia, provided that the transition cropping season between wheat harvest and rice transplanting is long enough.  相似文献   

18.
The effects of six phosphate (P) fertilizers in mobilizing and immobilizing water-soluble lead (Pb) were determined in a contaminated soil (Alfisol from Shaoxing) from China and four Australian soils (an Oxisol from Twonsville Queensland and three South Australian soils from Cooke Plains (Typic Palexeralf)), Inman Valley (Vertisol), and Two Wells (Natric Palexeralf). The fertilizers tested were single superphosphate (SSP), triple superphosphate (TSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), monocalcium phosphate (MCP), and dicalcium phosphate (DCP) to produce an initial P concentration of 1,000 mg/L. The Chinese soil contained 16,397 mg/kg total Pb, but the Australian soils were uncontaminated. The four Australian soils were each spiked with 1,000 mg Pb/kg soil (as Pb(NO3)2) and incubated for a month. Single superphosphate treatments decreased total soluble Pb in soil solution to 2–14 % of those of the nil-P (0P) treatment in the four Pb-spiked soils and to 48 % in the Chinese Pb-contaminated soil. The DAP treatment followed by the MAP treatment greatly increased the total soluble Pb in soil solution up to 135–500 % of the 0P treatment, except in the Two Wells soil. MCP could decrease the total soluble Pb in Cooke Plains, Inman Valley, Shaoxing, and Two Wells soils while increase it in the Queensland soil; DCP decreased the total soluble Pb in Cooke Plains and Queensland soils while increased it in the Shaoxing and Inman Valley soils. There were close relationships between the total soluble Pb, total soluble Al, and total soluble Fe in the water extracts of each. Soluble Al and Fe ions in soil solution increased soluble Pb concentrations. We conclude that not all phosphate fertilizers immobilize Pb in soils equally well. SSP and TSP are excellent Pb-immobilizing fertilizers, while MAP and DAP are strong Pb-mobilizing fertilizers. MCP and DCP are either Pb-immobilizing fertilizers or Pb-mobilizing fertilizers depending on their reactions with individual soils.  相似文献   

19.
Abstract

A three‐year field study was conducted on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudult) in North Alabama. The objective of the study was to evaluate the effects of winter grazing by cattle on the potassium (K) and starter fertilizer needs of cotton (Gossypium hirsutum L.) the following season. Grazed and non‐grazed treatments were established by planting a wheat (Triticum aestivum L.) cover crop in the fall and allowing cattle to graze half of the treatment area for 35 to 65 days in late winter‐early spring. After grazing, the grazed and non‐grazed wheat was killed and cotton was planted using a strip‐tillage system. Test areas had medium to high soil test ratings for K. Fertility treatments consisted of three rates of K (0, 37, and 74 kg K ha‐1), three methods of K application (surface broadcast; in‐row, band application at a depth of 30.5 cm; and surface banding using a spacing of 50.8 cm) and two rates of starter fertilizer (no starter and 168 kg#lbha‐l of a liquid 15–15–0). Seed cotton yields were affected by grazing of the winter cover crop prior to planting, but not by the method of K fertilizer application. During the two years that a yield reduction was observed, winter grazing reduced seed cotton yields by an average of 14%. Cotton responded to K rate only under the ungrazed system. During the first and second year of the test, an application of 37 kg K ha‐1 increased seed cotton yields by an average of 351 kg#lbha‐1. Starter fertilizer consistently gave slightly higher yields with a significant response occurring in two out of the three years.  相似文献   

20.
Bone char is a potential clean and renewable P fertilizer with Cd‐immobilization capabilities, but the P–Cd interactions in cropping of vegetable, grain, and tuber crops are unknown. In the present pot experiment bone char was evaluated on its effect on the growth and P supply of various crops (lettuce, wheat, potatoes) as well as its capability to reduce the uptake of Cd from a moderately Cd‐contaminated and P‐deficient soil (soil 1) and a highly Cd‐contaminated soil with sufficient P supply (soil 2). When averaging the dry‐matter yield over the treatments for each crop for the P‐sufficient soil 1, the following order was obtained: triple superphosphate (TSP) > diammonium phosphate (DAP) > BC, whereas for the soil 2 with sufficient P supply it was inverted with BC > DAP > TSP. The P‐deficiency resulted in a more pronounced effect of TSP and DAP on the plant growth, whereas P sufficiency in the soil promoted a crop‐quality‐enhancing effect of bone char. The Cd concentration in the consumption‐relevant plant parts was mostly insignificantly affected by treatments; however, the total Cd concentration in the whole plants tended to decrease with fertilizer addition for all crops in soil 1 even at very low bone‐char application levels. Similar results were obtained for soil 2 with an exception for the Cd concentration in potatoes, as the total Cd concentration was significantly increased in the TSP and DAP treatments. This most likely results from the introduction of Cd with TSP and DAP as they contained ≈ 27–28 mg Cd kg–1. Thus, this study demonstrated the potential of bone char as a clean P fertilizer, which can efficiently decrease the Cd contamination of potato on contaminated soils.  相似文献   

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