Energy balances and SOC and N stocks as affected by organic amendments and inorganic N fertilization in a semi-arid environment (IOSDV-Madrid)

A long-term field experiment (1984–2011), was conducted on a Calcic Haploxeralf from semi-arid central Spain to evaluate the combined effect of three treatments: farmyard manure (FYM), straw and control without organic amendments (WOA) and five increasing rates of mineral N on: (1) some energetic parameters of crop production, and (2) the effect of the different treatments on soil organic carbon (SOC) and total N stocks. Crop rotation included spring barley, wheat and sorghum. The energy balance variables considered were net energy produced (energy output minus energy input), the energy output/input ratio and energy productivity (crop yield per unit energy input). Results showed small differences between treatments. Total energy inputs varied from 9.86 GJ ha^?1 year^?1 (WOA) to 11.14 GJ ha^?1 year^?1 in the FYM system. For the three crops, total energy inputs increased with increasing rates of mineral N. Energy output was slightly lower in the WOA (33.40 GJ ha^?1 year^?1) than in the two organic systems (37.34 and 34.96 GJ ha^?1 year^?1 for FYM and straw respectively). Net energy followed a similar trend. At the end of the 27-year period, the stocks of SOC and total N had increased noticeably in the soil profile (0–30 cm) as a result of application of the two organic amendments. Most important SOC changes occurred in the FYM plots, with mean increases in the 0–10 cm depth, amounting an average of 9.9 Mg C ha^?1 (667 kg C ha^?1 year^?1). Increases in N stocks in the top layer were similar under FYM and straw and ranged from 0.94 to 1.55 Mg N ha^?1. By contrast, simultaneous addition of increasing rates of mineral N showed no significant effect on SOC and total N storage.     

A lysimeter study of the fate of fertilizer nitrogen in spring barley crops grown on shallow soil overlying Chalk: crop uptake and leaching losses

The objective of this work was to determine the fate of fertilizer nitrogen (labelled with nitrogen-15) applied to an undisturbed shallow soil overlying Chalk contained in 10 lysimeters (80 cm diameter, 135 cm deep). Measurements are reported of the nitrogen uptake by four spring barley crops and the rate and extent of leaching of nitrate beyond the roots. The crops were fertilized with 0, 80 or 120 kg N ha^?1 in each of four years, but only the first application in 1977 was labelled with nitrogen ?15. Rainfall and irrigation approximated to the long-term average, but in two treatments dry or wet spring conditions were imposed for the 10 weeks after sowing the first crop in 1977. The dry matter and grain yields of the spring barley crops varied from year to year in the ranges 8.7–14.0 t ha^?1 and 3.5–6.1 t ha^?1 respectively. The total nitrogen harvested in the crop approximated to the amount of nitrogen applied in each year with an apparent recovery of fertilizer in the range 38–76%. The recovery of nitrogen derived from fertilizer (labelled with nitrogen-15) was 46–54% in the first crop and after 2 years rapidly declined to below 1%. The total amount of nitrogen-15 labelled fertilizer recovered in four barley crops was 49–57% of that applied. Mean annual nitrate concentrations in water draining from the base of the lysimeters were in the range 11.8–26.7 mg N 1^?1 and did not differ significantly between nitrogen fertilizer treatments (0, 80 and 120 kg N ha^?1 a^?1). In all treatments nitrate concentrations varied considerably within each growing season, with a cycle of peaks and troughs. Annual losses of nitrate were in the range 39–128 kg N ha^?1, and the mean annual losses over the 4 years varied between lysimeters from 65 to 83 kg N ha^?1. Nitrogen-15 labelled nitrate was detected in the first drainage water collected in autumn following its spring application, 5 months earlier. Recovery of fertilizer-derived nitrogen in drainage water was greatest during the winter following the second barley crop, and was 3.4–3.7% of the nitrogen-15 applied. Over the 4 years of the experiment 6.3–6.6% of labelled fertilizer was accounted for in drainage water, representing 2–3% of the total nitrogen lost by leaching.     

Economic and environmental optimization of nitrogen fertilizer recommendations for cereals in Norway

Abstract

Results of 240 annual N fertilizer trials in 1991–2007 in spring and winter cereals are presented. On average, spring barley and oat yields increased little beyond 120 kg N ha^?1 in fertilizer. Somewhat higher figures were found for spring and winter wheat. Regression equations for yield and N uptakes in grain and straw were derived, related to N fertilizer input and the yield level in individual trials (indicator of yield expectancy). These equations accounted for 90% of the variation in yield and 80% of that in N uptake. Quadratic N responses were significant in all cases, as were interactions between N responses and yield level. They were verified with data from 27 separate trials performed in 2008–2010. The yield equations were used to calculate economically optimum N fertilizer levels with varying ratios of product price to fertilizer cost at contrasting levels of yield. The optimum N fertilizer level for barley and oats was found to increase by 8.3 kg N ha^?1 per Mg increase in expected yield. The equivalent figure in wheat was 16.3 kg N ha^?1. Optimum N fertilizer levels decreased by 4.1 and 6.7 kg N ha^?1, for barley/oats and wheat respectively, per unit increase in the cost/price ratio. The equations for N uptake were used to calculate simple N balances between fertilizer input and removal in crop products. Large N surpluses were indicated at low levels of yield expectancy, but the surplus declined markedly with increasing yield level, despite greater N fertilizer inputs at high yield. Calculations made for national average yield levels in recent years showed N surpluses of 50–60 kg N ha^?1 when only grain is removed and 25–40 kg N ha^?1 when straw is removed also. Limiting N input to obtain zero balance reduces yields considerably at average levels of yield expectancy.     

Catch crop strategy and nitrate leaching following grazed grass-clover

Cultivation of grassland presents a high risk of nitrate leaching. This study aimed to determine if leaching could be reduced by growing spring barley (Hordeum vulgare L.) as a green crop for silage with undersown Italian ryegrass (Lolium multiflorum Lam.) compared with barley grown to maturity with or without an undersown conventional catch crop of perennial ryegrass (Lolium perenne L.). All treatments received 0, 60 or 120 kg of ammonium‐N ha^?1 in cattle slurry. In spring 2003, two grass‐clover fields (3 and 5 years old, respectively, with different management histories) were ploughed. The effects of the treatments on yield and nitrate leaching were determined in the first year, while the residual effects of the treatments were determined in the second year in a crop of spring barley/perennial ryegrass. Nitrate leaching was estimated in selected treatments using soil water samples from ceramic cups. The experiment showed that compared with treatments without catch crop, green barley/Italian ryegrass reduced leaching by 163–320 kg N ha^?1, corresponding to 95–99%, and the perennial ryegrass reduced leaching to between 34 and 86 kg N ha^?1, corresponding to a reduction of 80 and 66%. Also, in the second growing season, leaching following catch crops was reduced compared with the bare soil treatment. It was concluded that the green barley/Italian ryegrass offers advantages not only for the environment but also for farmers, for whom it provides a fodder high in roughage and avoids the difficulties with clover fatigue increasingly experienced by Danish farmers.     

Yields of wheat and soil carbon and nitrogen contents following long-term incorporation of barley straw and ryegrass catch crops

Abstract. Three successive crops of winter wheat were grown on a sandy loam to test the residual effect of long‐term annual incorporation of spring barley straw at rates of 0, 4, 8 and 12 t ha^?1, and ryegrass catch crops with or without additions of pig slurry. Soil receiving 4, 8 and 12 t ha^?1 of straw annually for 18 years contained 12, 21 and 30% more carbon (C), respectively, than soil with straw removal, and soil C and nitrogen (N) contents increased linearly with straw rate. The soil retained 14% of the straw C and 37% of the straw N. Ryegrass catch‐cropping for 10 years also increased soil C and N concentrations, whereas the effect of pig slurry was insignificant. Grain yield in the first wheat crop showed an average dry matter (DM) increase of 0.7 t ha^?1 after treatment with 8 and 12 t straw ha^?1. In the two subsequent wheat crops, grain yield increased by 0.2–0.3 t DM ha^?1 after 8 and 12 t straw ha^?1. No grain yield increases were found after 4 t straw ha^?1 in any of the three years. Previous ryegrass catch crops increased yields of wheat grain, but effects in the third wheat crop were significant only where ryegrass had been combined with pig slurry. Straw incorporation increased the N offtake in the first wheat crop. In the second crop, only 8 and 12 t straw ha^?1 improved wheat N offtake, while the N offtake in the third wheat crop was unaffected. Ryegrass catch crops increased N offtake in the first and second wheat crop. Again, a positive effect in the third crop was seen only when ryegrass was combined with slurry. Long‐term, annual incorporation of straw and ryegrass catch crops provided a clear and relatively persistent increase in soil organic matter levels, whereas the positive effects on the yield of subsequent wheat crops were modest and transient.     

Optimizing seed crops of common bent (Agrostis capillaris) by sowing rate

Abstract

As part of a project to stimulate Norwegian seed production of common bent (syn. browntop, US: colonial bentgrass, Agrostis capillaris L. syn. A.tenuis Sibth.) field trials comparing sowing rates of 2.5, 5.0, 7.5 or 10 kg ha^?1 were conducted at Landvik, south-east Norway, (58°N) from 1989 to 1994. Three trials were laid out of the forage cultivar ‘Leikvin’ and three trials of the lawn cultivar ‘Nor’, each trial being harvested for three consecutive years. While the average per cent ground cover in spring increased from 87% at 2.5 kg ha^?1 to 94–96% at 7.5 kg ha^?1, seed yields decreased with increasing sowing rate in both cultivars. On average for all harvests, quadrupling the sowing rate from 2.5 to 10 kg ha^?1 reduced seed yield by 9% in ‘Leikvin’ and 15% in ‘Nor’, the stronger effect probably being associated with a greater competition between tillers in the lawn cultivar. Seed yield reductions with increasing sowing rate showed no relationship with crop age, but were less accentuated for crops undersown in spring wheat in a dry year than for crops established without cover crop in years with ample rainfall in early summer. Increasing sowing rates reduced plant height and panicle number in ‘Nor’, but had no effect on seed weight or germination in any of the cultivars. It is concluded that seed crops of common bent should be established with a sowing rate of 2–5 kg ha^?1, with the lowest rate in lawn cultivars, under ideal seedbed conditions and when seed crops are sown without cover crop.     

Optimum application level of winter cover crop biomass as green manure under considering methane emission and rice productivity in paddy soil

The combined seeding and cropping of non-leguminous and leguminous cover crops during the cold fallow season is recommended as an important agronomic practice to improve total biomass productivity and soil fertility in mono-rice (Oryza sativa L.) cultivation system. However, application of plant residues as green manure can increase methane (CH₄) emission during rice cultivation and affect rice quality and productivity, but its effects are not well examined. In this field study, the mixture of barley (Hordeum vulgare R.) and hairy vetch (Vicia villosa R., hereafter, vetch) seeds with 75 % recommended dose (RD 140 kg ha^?1) and 25 % RD (90 kg ha^?1), respectively, were seeded after rice harvesting in late November, 2010, and harvested before rice transplanting in early June 2011. Total aboveground biomass was 36 Mg ha^?1 (fresh weight basis with 68 % moisture content), which was composed with 12 Mg ha^?1 of barley and 24 Mg ha^?1 of vetch. In order to determine the optimum recycling ratio of biomass application that can minimize CH₄ emission without affecting rice productivity, different recycling ratios of 0, 25, 50, 75, and 100 % of the total harvested biomass were incorporated as green manure 1 week before rice transplanting in a typical temperate paddy soil. The same rates of chemical fertilizers (N–P₂O₅–K₂O?=?90–45–58 kg ha^?1) were applied in all treatments. Daily mean CH₄ emission rates and total CH₄ fluxes were significantly (p?<?0.05) increased with increasing application rates of cover crop biomass. Rice productivity also significantly (p?<?0.05) increased with biomass application, but the highest grain yield (53 % increase over the control) was observed for 25 % recycling. However, grain quality significantly (p?<?0.05) decreased with increasing cover crop application rates above 25 % recycling ratio, mainly due to extended vegetative growth periods of rice plants. Total CH₄ flux per unit grain yield, an indicator used to simultaneously compare CH₄ emission impact with rice production, was not statistically different between 25 % biomass recycling ratio and the control but significantly increased with increasing application rates. Conclusively, the biomass recycling ratio at 25 % of combined barley and vetch cover crops as green manure might be suitable to sustain rice productivity without increasing CH₄ emission impact in mono-rice cultivation system.     

Strategies for high nitrogen production and fertilizer value of plant-based fertilizers

Background

Organic vegetable production has a demand for alternative fertilizers to replace fertilizers from sources that are not organic, that is, typically animal-based ones from conventional farming.

Aims

The aim of this study was to develop production strategies of plant-based fertilizers to maximize cumulative nitrogen (N) production (equal to N yield by green manure crops), while maintaining a low carbon-to-nitrogen (C:N) ratio, and to test the fertilizer value in organic vegetable production.

Methods

The plant-based fertilizers consisted of the perennial green manure crops—alfalfa, white clover, red clover, and a mixture of red clover and ryegrass—and the annual green-manure crops—broad bean, lupine, and pea. The crops were cut several times at different developmental stages. The harvested crops were used fresh or pelleted as fertilizers for field-grown white cabbage and leek. The fertilizer value was tested with respect to biomass, N offtake, N recovery, and soil mineral N (N_min). Poultry manure and an unfertilized treatment were used as controls.

Results

The cumulative N production of the perennial green manure crops ranged from 300 to 640 kg N ha^–1 year^–1 when cut two to five times. The highest productions occurred at early and intermediate developmental stages, when cut three to four times. Annual green manure crops produced 110–320 kg N ha^–1 year^–1, since repeated cutting was restricted. The C:N ratio of the green manure crops was 8.5–20.5, and increased with developmental stage. The fertilizer value of green manure, as measured in white cabbage and leek, was comparable to animal-based manure on the condition that the C:N ratio was low (<18). N recovery was 20%–49% for green manure and 29%–42% for poultry manure. A positive correlation was detected between soil N_min and vegetable N offtake shortly after incorporating the green manure crops, indicating synchrony between N release and crop demand.

Conclusions

Plant-based fertilizers represent highly productive and efficient fertilizers that can substitute conventional animal-based fertilizers in organic vegetable production.     

Long-term fertilizer trials on loam soil at M⊘ystad,south-eastern Norway: Crop yields,nutrient balances and soil chemical analyses from 1983 to 2003

Abstract

Factorial combinations of N, P and K fertilizer have been compared with the use of farmyard manure at M?ystad since 1922 in a seven-year crop rotation (3 ley, oat, potato, wheat, barley). Until 1982, low inputs of N fertilizer (22 kg ha^?1) were used. In 1983, they were brought into line with current farming practice. This paper presents the results of three subsequent rotations. Yields without any fertilizer were on average 48% of those with 100 kg N ha^?1 in compound fertilizer, whilst those with 20, 40 and 60 Mg ha^?1 farmyard manure were 81, 87 and 90%, respectively. Yields with other combinations of N, P and K declined in the order NP, NK, N, PK and K. When NPK fertilizer was used, apparent recoveries of applied fertilizer were close to 50% for N and K, and around 40% for P. Much lower values were found for nutrients applied singly. Balance between N supply and removal was indicated at rates of about 60 kg N fertilizer ha^?1 in potatoes, 75 kg ha^?1 in cereals and 90 kg ha^?1 in leys. A surplus of P was found in all crops at all N levels, and of K in cereals and potatoes. In leys, K balance was achieved with an N supply of 90 kg N ha^?1. Nutrient balance was indicated at a little below 20 Mg ha^?1 yr^?1 farmyard manure. Larger manure applications gave large nutrient surpluses, particularly of N. Soil reaction remained close to neutral with the use of calcium nitrate and manure, but declined with the use of ammonium nitrate. Manure use gave the highest amounts of available P, K and Mg in soil. Similar increases in total inorganic P were found with manure use as with fertilizer use, but amounts of organic P and total K were little affected.     

Wirkung der Phosphatdüngung in einem 40jährigen Dauerversuch auf einer Sandlöß-Braunschwarzerde in Halle

Effect of differential P fertilizer application over a period of 40 years in a long-term field experiment on a Phaeozem near Halle, Germany P fertilizer in three forms was applied at 0 (P₀), 15 (P₁) and 45 (P³) kg ha^?1 P per annum to a relation lucerne — lucerne — potatoes — winter rye — sugar beet — spring barley. The experiment was laid down in 1949 near Halle on Phaeozem soil containing 57 mg total P and 8.5 mg DL-P per 100 g soil (0–20 cm) and with pH 6.0 (0.1 M KCl). Small differences between treatments were first observed only after 20 years. Since then the effects of treatment increased but even after the 7th cycle (1982–1987) the maximum effect was <8 cereal units (CU) per ha. The crops most responsive to P were: lucerne (in the year of sowing), potatoes and sugar beet. Over the period 1977–1988, annual P removal exceeded P input by 23 and 9 kg ha^?1 P for treatments P₀ and P₁ respectively; on treatment P³, P input exceeded removal by 19 kg ha^?1 per annum. DL-P on treatment P₀ in 1979 was 3.5–4.0 mg per 100 g, insufficient to support high yields. A level of 5–6 mg DL-P per 100 g soil, as found in treatment P₁ is required for sustainable high yield. Change in total soil P content corresponded with the P balance (input — withdrawal) only on treatment P³. The lack of correspondence on treatments P₀ and P₁ suggests that crops obtained much of their P requirement from subsoil.     

Crop stand density enhances competitive ability of spring barley (Hordeum vulgare L.)

Abstract

The aim of the research was to establish weediness, competitive ability and productivity of the crop. The experimental object was agrophytocenoses of spring barley – Hordeum vulgare L. – crop of spring barley ‘Aura’ and unsown soil, and weeds growing in them. The crop was formed sowing 0, 120, 200 and 280 kg ha^?1 (0, 2.7, 4.5 and 6.2 million seeds per ha^?1 respectively) seeds of spring barley ‘Aura’. Spring barley crop was not harrowed and herbicides were not applied. In the field experiment estimates were made of changes of weeds and spring barley inter- and within- species competition optimizing crop density. During three years of field experiment in the crop of spring barley annual weeds prevailed at 88–99%, such as Chenopodium album, Stellaria media, Erysimum cheiranthoides. Perennial weeds formed 1–12% of the crop weeds, such as Sonchus arvensis, Cirsium arvense, Equisetum arvense. General number of weed species in spring barley crops varied from 13 to 21. Weed abundance proportionally declined in the crops of higher density, hence, higher seed rate should be recommended for organic agriculture where weeds are controlled in non-chemical ways. Consistently increasing barley stand density, the competition between species (spring barley with weeds) gradually turned into competition within species (between barley plants) when a higher number of weaker and non-productive stems started forming. Spring barley yield did not significantly depend on the stand density. Increasing stand density enhanced cultivated crop yield to a certain level (200 kg ha^?1), since an increase in spring barley plant number resulted in the reduction in weight per plant and 1000 grain weight, which was compensated by an increase in the number of spring barley plants. Different spring barley density had an essential influence on the chemical composition of weeds which was similar to that of spring barley. Weeds accumulated the greatest amount of crude proteins, crude fat and crude fibre growing without spring barley.     

Enhancing Environmental Performance with Winter Cover Cropping after Potato Harvest in Eastern Canada

ABSTRACT

In humid climates, the risk of nitrate leaching and topsoil loss due to erosion is high on bare soil in the fall after potato (Solanum tuberosum L.) harvest and in the spring with snowmelt. This 2-year study (2016–2017) compared three winter cover crops. Two of these are used as cash crops (winter rye [Secale cereale L.], winter wheat [Triticum aestivum L.]), and one is a winter-killed cover crop (spring barley, Hordeum vulgare L.). They were all seeded on two dates after potato harvest (end of September or first week of October) in Prince Edward Island, Canada. The measured parameters included soil nitrate measured at different times in fall and in the following spring and summer, splash detachment, C and N contents in splashed sediments, cereal straw dry matter yield, and cereal grain yield. In both years, all winter cover crops decreased splash detachment compared with the no winter cover control, with winter rye having the greatest reduction. A similar trend was observed for C and N contents in splashed sediments. There was a trend toward lower soil nitrate following winter cover crops in comparison with bare soil, but the trend was not consistent across trials and sampling dates. Winter wheat grain yield ranged from 4.5 to 7.6 Mg ha^?1, while that associated with winter rye ranged from 3.2 to 5.1 Mg ha^?1. Therefore, winter cereal seeded after potato harvest can constitute a good source of revenue while mitigating the risk of soil erosion and reducing nitrate leaching in some cases.     

Contributions from carbon and nitrogen in roots to closing the yield gap between conventional and organic cropping systems

This study investigates the effect of different crop rotation systems on carbon (C) and nitrogen (N) in root biomass as well as on soil organic carbon (SOC ). Soils under spring barley and spring barley/pea mixture were sampled both in organic and conventional crop rotations. The amounts of root biomass and SOC in fine (250–253 μ m), medium (425–250 μ m) and coarse (>425 μ m) soil particulate organic matter (POM ) were determined. Grain dry matter (DM ) and the amount of N in harvested grain were also quantified. Organic systems with varying use of manure and catch crops had lower spring barley grain DM yield compared to those in conventional systems, whereas barley/pea showed no differences. The largest benefits were observed for grain N yields and grain DM yields for spring barley, where grain N yield was positively correlated with root N. The inclusion of catch crops in organic rotations resulted in higher root N and SOC (g C/m²) in fine POM in soils under barley/pea. Our results suggest that manure application and inclusion of catch crops improve crop N supply and reduce the yield gap between conventional and organic rotations. The observed positive correlation between root N and grain N imply that management practices aimed at increasing grain N could also increase root N and thus enhance N supply for subsequent crops.     

Performance of spring barley varieties and variety mixtures as affected by manure application and their order in an organic crop rotation

Abstract

In order to obtain a high and stable yield of organic spring barley, production should be optimized according to the specific environment. To test the performance of spring barley varieties under varying cropping conditions, a field experiment was carried out in 2003 and 2004 in a six-field mixed organic crop rotation. We investigated the choice of variety, the order in a rotation, and the application of manure (slurry and farmyard manure; 0 to 120 total-N ha^?1) on grain yields of six selected varieties with different characteristics grown in either pure stands or in two spring barley mixtures, each consisting of three varieties.

Average grain yield of the barley varieties varied between 3.3 t DM ha^?1 and 4.1 t DM ha^?1. Grain yields of the two mixtures were 4.0 and 3.6 t DM ha^?1, respectively. The varieties/mixtures interacted with crop order and year. Foliar diseases were more severe in the barley following grass-clover with large annual differences in the individual diseases. Despite different rooting depths and nutrient uptake patterns, there was no interaction between variety/mixture and the manure input regarding grain yield.

In the 1^st year after grass-clover, one of the two mixtures gave higher grain yield than the average yield of the individual varieties in the mixture. This was not the case in the 4^th year after grass-clover and for the second variety mixture. Thus, although the present results did not indicate that some barley varieties were better adapted to conditions with low manure input than others, variety mixtures that give a robust and stable organic production may potentially be developed.     

The effect of organic and chemical fertilizers on oilseed rape productivity and weed competition in short rotation

Abstract

A two-year field experiment was conducted to investigate the impact of short crop rotation and organic amendments on rapeseed yield under weed competition conditions. The primary experimental plots consisted of either triticale or pea as a prior crop, consisting of four subplots with either 25 tons of composted cattle manure (CCM), 150?kg urea N ha^?1 (N), 25 tons composted cattle manure + 75?kg urea N ha^?1 (CCM?+?N), or no urea N or manure added as the control (C0). Rapeseed seed yield was not significantly affected by previous crops, except for rapeseed grown after pea which had slightly higher seed yield (2058?kg ha^?1) than those grown after triticale (1942?kg ha^?1). Plants that received CCM?+?N produced the highest amount of seed yield (2447?kg ha^?1), but were not significantly different from plants that received just urea N (2218?kg ha^?1). Weeds gained more biomass when the previous crop was pea compared to those whose previous crop was triticale. Weeds in plots that received CCM?+?N produced the greatest biomass, followed by N, and CCM plots, respectively.     

Effect of phosphorus management in rice–mungbean rotations on sandy soils of Cambodia

Nitrogen (N) and phosphorus (P) deficiencies are key constraints in rainfed lowland rice (Oryza sativa L.) production systems of Cambodia. Only small amounts of mineral N and P or of organic amendment are annually applied to a single crop of rainfed lowland rice by smallholder farmers. The integration of leguminous crops in the pre‐rice cropping niche can contribute to diversify the production, supply of C and N, and contribute to soil fertility improvement for the subsequent crop of rice. However, the performance of leguminous crops is restricted even more than that of rice by low available soil P. An alternative strategy involves the application of mineral P that is destined to the rice crop already to the legume. This P supply is likely to stimulate legume growth and biological N₂ fixation, thus enhancing C and N inputs and recycling N and P upon legume residue incorporation. Rotation experiments were conducted in farmers' fields in 2013–2014 to assess the effects of P management on biomass accumulation and N₂ fixation (δ¹⁵N) by mungbean (Vigna radiata L.) and possible carry‐over effects on rice in two contrasting representative soils (highly infertile and moderately fertile sandy Fluvisol). In the traditional system (no legume), unamended lowland rice (no N, + 10 kg P ha^?1) yielded 2.8 and 4.0 t ha^?1, which increased to 3.5 and 4.7 t ha^?1 with the application of 25 kg ha^?1 of urea‐N in the infertile and the moderately fertile soil, respectively. The integration of mungbean as a green manure contributed up to 9 kg of biologically fixed N (17% Nfda), increasing rice yields only moderately to 3.5–4.6 t ha^?1. However, applying P to mungbean stimulated legume growth and enhanced the BNF contribution up to 21 kg N ha^?1 (36% Nfda). Rice yields resulting from legume residue incorporation (“green manure use”–all residues returned and “grain legume use”–only stover returned) increased to 4.2 and 4.9 t ha^?1 in the infertile and moderately fertile soil, respectively. The “forage legume use” (all above‐ground residues removed) provided no yield effect. In general, legume residue incorporation was more beneficial in the infertile than in the moderately fertile soil. We conclude that the inclusion of mungbean into the prevailing low‐input rainfed production systems of Cambodia can increase rice yield, provided that small amounts of P are applied to the legume. Differences in the attributes of the two major soil types in the region require a site‐specific targeting of the suggested legume and P management strategies, with largest benefits likely to accrue on infertile soils.     

Effect of Poultry Manure on Yield and Nutrient Composition of Sweet Basil (Ocimum basilicum L.)

Poultry manure is one of the best organic fertilizers available and is an extremely valuable resource, organic matter content, exchangeable cations, cation exchange capacity, and percent base saturation. Ocimum basilicum L. (sweet basil) is an essential oil producing crop used in culinary and fragrance applications. The objective of this present study was to evaluate the effects of organic poultry manure and conventional fertilization on plant growth, yield and inorganic matter content of sweet basil. In this context, the different doses of chicken and turkey manure (7.5, 10, 12.5, 15 t ha^?1) with a control (no manure) and conventional fertilization were applied with sowing. The highest fresh and dry weights were obtained from the plants grown with turkey and chicken manure at a rate of 10–12.5 t ha^?1. The most of the nutrient content varied significantly with organic poultry manure applications. Overall, basil plants fertilized with turkey manure at a rate of 10–12.5 t ha^?1 and 7.5 t ha^?1 chicken manure dose accumulated greater concentrations of potassium (K) and magnesium (Mg). The results from this study demonstrated that organic or conventional fertilizer can alter fresh or dry weight, and the nutrient content.     

Leaching and crop uptake of N, P and K from organic and conventional cropping systems on a clay soil

In this study, three types of cropping systems with different nutrient management strategies were studied on a clay soil with the aim of comparing leaching of N, P and K and obtaining knowledge on nutrient budgets. A conventional cropping system with cereals and application of mineral fertilizers (CON) was compared with two organic cropping systems, one without animal manure in which green manure crops were used for N supply (OGM) and one where animal manure (cattle slurry) was applied (OAM). Leaching and crop uptake of N, P and K, and soil mineral N were measured in pipe‐drained plots over a 6‐year period. The mean annual leaching loads of N were moderate and did not differ significantly (P > 0.05) between treatments; 13 kg N ha^?1 in CON, 11 kg N ha^?1 in OGM and 7.4 kg N ha^?1 in OAM. Average annual P leaching showed greater variation than N leaching and was significantly greater in OGM (0.81 kg ha^?1 year^?1) than in CON (0.36 kg ha^?1) and OAM (0.41 kg ha^?1). For all cropping systems, removal in harvested crops was the most important export of nutrients from the field and constituted between 80 and 94% of total N outputs (harvested and leached N). Yields of cereals in the organic systems were considerably less (15–50%) than in the CON system, leading to a less efficient use of N than in the conventional system.     

Evaluation of Compost for Use as a Soil Amendment in Corn and Soybean Production

The purpose of this research project was to 1) evaluate rate of compost application and 2) to compare compost with uncomposted raw material and inorganic fertilizer N application upon maize and soybean growth and productivity, and upon soil characteristics. During the first three years of the study, the source of uncomposted material and compost was food waste and ground newsprint. During years 4 to 9 of the study, the source of uncomposted material and compost was dairy cow manure and wood chips. Application rates in field site 1 were 0, 11.2, 22.4, 33.6 and 44.8 Mg ha^?1 compost, 44.8 Mg ha^?1 uncomposted material and 140 kg ha^?1 fertilizer N (as urea). Application rates in field site 2 were 0, 22.4, 44.8, 67.2 and 134.4 Mg ha^?1 compost, 134.4 Mg ha^?1 uncomposted manure and 180 kg ha^?1 fertilizer N (dry matter basis). The high rates of compost application significantly raised organic matter levels, and available P and K compared to inorganic fertilizer N. Uncomposted manure and increasing compost application rates significantly increased grain yield, number of kernels per plant and plant weight. Composting significantly reduced pathogen indicator bacteria concentrations. The data of this study suggest that on these high organic matter soils 22.4 Mg ha^?1 to 44.8 Mg ha^?1 are optimal compost application rates.     

Improving organic C and N fractions in a sulfur-deficient soil with S fertilization

A field experiment was conducted over 9?years (1999 to 2007 growing seasons) in northeastern Saskatchewan on a S-deficient Gray Luvisol (Typic Haplocryalf) soil. The objective was to determine the relative effectiveness of N alone versus combined annual application of N (120?kg N?ha^?1) and S (15?kg S?ha^?1) fertilizers to a wheat–canola rotation on storage of total organic C (TOC) and N (TON) and on the light fraction organic C (LFOC) and N (LFON) in soil. Compared to N alone, annual applications of S fertilizer in spring in a combination with N resulted in an increase in soil of TOC (by 2.18?Mg C?ha^?1), TON (by 0.138?Mg N?ha^?1), LFOC (by 1,018?kg C?ha^?1), and LFON (by 42?kg N?ha^?1). The relative increases in organic C or N due to S fertilizer application were much higher for the light organic fractions (36.9% for LFOC and 27.5% for LFON) than for the total organic fractions (9.2% for TOC and 7.3% for TON). The findings demonstrate the importance of a balanced/combined application of N and S fertilizers to crops in storing more organic C and N in this S-deficient soil.