Soil Conservation Tillage Effects on Yield and Water Use Efficiency on Irrigated Crops in Central Italy

Despite possible agronomic and environmental benefits, the diffusion of soil conservation tillage systems in Italy is currently rather low. The aim of this study was to compare the performance of different soil tillage techniques, in an effort to identify suitable soil management options for irrigated crops in Central Italy. An experiment was carried out on maize and soybean from April to October in two consecutive years (1993 and 1994) in Maccarese (a coastal location near Rome). The systems compared were: conventional mouldboard ploughing (CT), minimum tillage, ridge tillage and no-tillage (NT). In 1993, actual crop evapotranspiration was measured throughout the growing season on NT and CT soybean, using a micrometeorological technique.
No significant differences due to soil tillage were found for grain yield and yield irrigation water use efficiency (IWUEy), except for soybean in 1994, in which yields and IWUEy were 59 % higher on conservation tillage treatments compared with CT. In 1994 soybean yield water use efficiency was 10.1 and 9.5 kg ha⁻¹ mm⁻¹ for NT and CT respectively. The results suggest that the adoption of soil conservation tillage is feasible, for the specific cropping system, with equivalent or better performances as conventional tillage.     

Analysis of Growth and Productivity of Indian Mustard (Brassica juncea) in Relation to FYM, Nitrogen and Source of Fertilizer

A field experiment was conducted during the winter seasons of 1992–93 and 1993–94 at Anand to study the effect of FYM, nitrogen and source of fertilizer on growth and yield of mustard [ Brassica juncea (L.) Czernj & Cosson]. The results showed significant variation in leaf area index (LAI), crop growth rate (CGR), dry matter production and seed yield. The direct effect of farmyard manure (FYM) was conspicuous in improving the growth of mustard. FYM application at 10 tonnes ha⁻¹ significantly increased the LAI, CGR and dry matter accumulation per plant at almost all the stages during first year study (1992–93) and in pooled analysis. Similarly, nitrogen application registered maximum LAI, CGR at 75 kg level and RGR and NAR at 50 kg level at almost all the during both years. Sulphur carrying source (Ammonium sulphate plus single super phosphate) increased all stages growth characters. Maximum dry matter accumulation per plant and seed yield were recorded with highest levels of FYM (20 tonnes ha⁻¹), N (75 kg ha⁻¹) and source having S. Seed yield was strongly associated with LAI and dry matter accumulation per plant at all the stages.     

Effect of Integrated Use of Farmyard Manure and Sulphur in a Soybean and Wheat Cropping System on Nodulation, Dry Matter Production and Chlorophyll Content of Soybean on Swell-Shrink Soils in Central India

In a 3-year experiment on a Typic Haplustert low in soil test sulphur (S), the response to applied farmyard manure (FYM) and S was studied in terms of the nodule production, nodule dry weight, chlorophyll content, dry matter production and seed yield of soybean. FYM was applied to soybean at four levels (0–16 t ha⁻¹). S as gypsum was also applied at four levels (0–60 kg ha⁻¹) to both soybean and wheat every year. Both total and active nodule production, nodule dry weight, dry matter production and seed yield of soybean were increased significantly by the application of both FYM and S. However, the proportion of total nodules to active nodules fell sharply for applications higher than 8 t FYM and 40 kg S ha⁻¹.     

Pearl Millet Phenology and Growth in Relation to Thermal Time under Arid Environment

Pearl millet ( Pennisetum glaucum L.R.Br.) hybrid MH 179 was grown under two moisture regimes viz., optimal moisture and rainfed conditions. The field experiment was continued for three consecutive rainy seasons to quantify the pearl millet development with thermal time. The possible influence of variation in natural sowing date on the relationships between crop development and thermal time have been described. At cardinal temperatures of 10°C (base temperature below which pearl millet development ceases), 33°C (optimal temperature for development) and 45°C (maximum temperature at and above which no development takes place), the crop required 1490–1794°Cd thermal time to reach physiological maturity. The thermal time requirement for different developmental stages was influenced by the sowing time and moisture availability during the growing season of the crop.
The leaf tip appearance on the main shoot of pearl millet in relation to thermal time was almost linear under both moisture conditions requiring about 44–50°Cd ± 2.6 °Cd leaf⁻¹, till the appearance of the flag (last) leaf. However, leaf tip appearance on primary tillers was slightly slower and required 53-58°Cd ± 4.7°Cd for each new leaf. Appearance of first primary tiller was later (at 320°Cd after emergence) under the rainfed condition as compared to the crop under the optimal moisture (at 250°Cd).Thereafter, the tiller appearance in relation to thermal time under both moisture conditions was at a linear rate of about 53-56°Cd ± 9.5°Cd tiller⁻¹.
Effect of microclimatic variations, canopy temperature, radiation and photoperiod on the phenology-thermal time relationships have been discussed under both the moisture conditions.     

Effects of Fungicide on Grain Yield of Barley Grown in Different Cropping Systems

The effect of fungicides and their combination on yield of barley under different nitrogen, slurry and tillage treatments was investigated at Hohenschulen Experimental Station near Kiel, Germany in 1991–97. Various fungicide treatments (no fungicide, and treatment with stem, leaf and ear fungicides and combinations of these), two nitrogen levels (120 and 240 kg N ha⁻¹), two tillage systems (minimum and conventional tillage) and four slurry applications (no application, and autumn, spring and autumn plus spring applications) were used. On average, fungicide application increased barley yield by 1.1 t ha⁻¹. The fungicide treatments could be classified into four types: (1) fungicides against stem diseases, which slightly increased yield by 0.25 t ha⁻¹, very similar to the results for the untreated control; (2) leaf fungicides and ear fungicides applied separately, and fungicides against a combination of stem and leaf diseases, which increased yield by 1.0 t ha⁻¹ on average; (3) fungicides against a combination of ear and stem diseases, which increased the yield by 1.22 t ha⁻¹, and (4) fungicides against a combination of leaf and ear diseases and a combination of stem, leaf and ear diseases, which increased yield by 1.59 t ha⁻¹ on average. The effects of fungicide on the yield were modified by crop husbandry. It can be concluded that application of fungicides against a combination of leaf and ear diseases could increase barley yield and reduce yield variation.     

Effect of Sowing Season and Seeding Rate on the Morphological Traits and Yields in Pea Cultivars of Differing Leaf Types

Determination of optimal N-fertilization rates, N_OR , for crop production that minimize risk of environmental degradation require accurate application of a response model. Several models are available to describe crop yield response to N fertilization. The objective of this work was to compare the relative accuracy of a quadratic, f(N _Q), a modified Mitscherlich, and tanh( N ) models on 48 data sets. Data were collected from a Tara silt loam (fine-silty, mixed, frigid Pachic Udic Haploboroll) over a 6-year period using two maize ( Zea mays L.) hybrids and four tillage treatments, mouldboard plough, chisel plough, ridge tillage and no-tillage. In about one-third of the cases, all models performed about equally well. Generally, the tanh( N ) and modified Mitscherlich models gave better fit between N rate and grain yield data. The N_OR, ranged from about 140 to 170 kg ha⁻¹ for the modified Mitscherlich model, 136 to 184 kg ha⁻¹ for the tanh( N) function, and 124 to 173 kg ha⁻¹ using the f(N _Q) model. Estimated grain yields at these rates ranged between 6.58 ± 1.30 to 7.59 ± 1.69 Mg ha⁻¹ for the 90-day Minnesota maturity rated (MR) hybrid and between 7.52 ± 2.40 to 8.72 ± 1.70 Mg ha⁻¹ for the 95-day MR hybrid.     

Effect of Irrigation and N-Fertilization (Fertigation) Scheduling on Tomato in the Jordan Valley

Tomato ( Lycopersicon esculentum mill. cv. Petopride ) is the most important vegetable crop in Jordan; its production is characterized by inadequate irrigation and fertilization practices, especially under open field conditions. A field study was carried out to determine the effect of different irrigation intervals and different N-fertilizer doses on water use, tomato yields and residual soil nitrogen.
Results indicated significant differences in water use and tomato yields between irrigation treatments. Highest yield (51.4 ton ha⁻¹) was obtained under three irrigations per week with 504 mm total water supply, whereas under irrigation once a week 35.3 ton ha⁻¹were produced with 353 mm total water supply. There were no significant differences in yield between fertigation with ten equal time intervals and fertigations with intervals as per crop requirements, the yields were 47.1 ton ha⁻¹ and 44.5 ton ha⁻¹, respectively. However, yield was significantly lower with three fertigations at equal intervals and equal doses (35.8 ton ha⁻¹) throughout the season. There were no significant differences between mineral nitrogen forms in terms of yield effects. Significant irrigation effects were observed on total soil nitrogen. Residual soil N was 0.052% in the surface layer (0–30 cm), and 0.030% in the subsurface layer (30–60 cm).     

The Effect of Bradyrhizobium Strains on Monocropped and Intercropped Soybean (Glycine max L. Merr.) Biomass and Protein

An experiment was conducted during rainy season (April-August) of 1994 and 1995 to assess the performance of rice, maize, sesame, greengram and blackgram grown in sole and intercropping system on Gangetic alluvial upland (Entisol) in West Bengal. India. All intercropping systems except sesame + rice had higher total productivity in terms of rice equivalent yield and net returns than all the sole crops. However, maximum advantage was obtained from paired row planted maize blackgram system followed by maize + sesame, maize + blackgram and paired row planted rice + blackgram. Paired row planted maize + blackgram increased land use efficiency (42%), rice equivalent yield (2955 kg ha⁻¹), monetary return (Rs. 7294 ha⁻¹), income equivalent ratio (1.22), monetary advantage (Rs. 3701 ha⁻¹) compared with other cropping systems, which proved to be the most efficient system. The same treatment also indicated a modest competitive ratio (4.65:0.21) and gave a good value for the product of crowding coefficient (8.28).     

Maximizing Sugarcane Yield by Increasing Plant Population Density, Minimizing NO3-N Leaching and Improving Soil Organic Matter in Different Crop Rotations

In a field experiment conducted during 1992–95 at Lucknow, India, sugarcane was planted in rows 60 and 90 cm apart in three crop rotations (rice-sugarcane-ratoon, Sesbania aculeata for green manure-sugarcane-ratoon, and cowpea-sugarcane-ratoon) with 0, 150 and 300 kg N ha⁻¹ as urea either with or without farmyard manure (FYM) at 10 t ha⁻¹. Sugarcane yields were significantly greater in the Sesbania rotation than in the other because of a larger N uptake. N uptake of the crop was significantly affected by soil organic carbon, and available N and K contents. Ratoon yields, however, were largest in the cowpea sequence followed by the rice rotation, probably due to a prolonged residual effect of cowpea and rice root residues. The residual effect of a Sesbania green manure was negligible as demonstrated by the low NO₃-N content of the soil profile after sugarcane harvest compared to the other two crop sequences. The total cane productivity (main sugarcane plus ratoon) was greater (156 t ha⁻¹) in the cowpea rotation than the Sesbania (152 t ha⁻¹) and rice (140 t ha⁻¹) rotations.     

Effect of the Organic Residues of Miscanthus × giganteus on the Soil Organic Matter Level of Arable Soils

During a complex investigation programme on the evaluation of the long-term ecological impact of cropping Miscanthus , the substrate composition of residues in 4–8-year-old stands of Miscanthus × giganteus and the contribution of Miscanthus residues to soil organic matter (SOM) were investigated. Only about 50 % of the above-ground biomass produced yearly was suitable for harvest because of pre-harvest losses and harvesting residues. The potential supply to SOM was therefore 3.1 t ha⁻¹ carbon annually accumulated by the litter, and 9.1 t ha⁻¹ carbon accumulated by rhizomes and roots in the long term. These organic residues mineralized differently in laboratory experiments at generally high rates of decomposition. Analysis of soluble portions of the organic substance of these biomass components by hydrolysis with hot water, 2 % HCl and 80 % H₂SO₄ confirmed the results. Setting the SOM effect of an equivalent farmyard-manure (FYM) supply to 100 %, Miscanthus residues reached 60 % (stubble, rhizomes), 80–90 % (pre-harvest losses) and 100 % (roots). Established Miscanthus stands are able to produce about 8.2 t ha⁻¹ organic substance, which is comparable with FYM in terms of SOM impact. This kind of calculation showed higher values for Miscanthus than for the agricultural crops investigated to date. An SOM increase of about 0.5 % on sandy soils and 0.2 % on silt soil was determined after 6–8 years of cropping Miscanthus × giganteus .     

Effect of Zinc and Iron Supply on Production Potential of Rice (Oryza sativa L.)

A field experiment was performed to study the effect of zinc and iron supply on grain yield in four promising varieties of rice ( Oryza sativa L.) viz. IR-20, Jaya, Pusa 2–21, and IET-1444. Three doses of ZnSO₄ or FeSO₄ (0, 20 or 40 kg ha⁻¹) along with all possible combinations were investigated. The varietal differences were significant in grain yield ha⁻¹. The grain yield increased with the dose of zinc and Jaya but not significantly in IR-20. The increase in grain yield was more significant and dose dependent in IET-1444 than in Jaya in response to iron application.     

Effect of Integration of Fertilizer and Green Manure Nitrogen on Yield Attributes, Nitrogen Uptake and Yield of Lowland Rice (Oryza sativa L.)

Field experiments were conducted at Tamil Nadu Rice Research Institute, Aduthurai, India, during the wet seasons of 1992 and 1993 to study the effect of full and partial substitution of fertiliser N with green manure N (Sesbania rostrata) on nitrogen uptake, yield attributes and yield of rice. The experiment consisted of eight treatments with two levels of N (100 and 200 kg ha⁻¹) and three sources of N application viz., fertilizer, integrated (1:1 fertilizer and green manure N) and green manure N compared to the recommended practice (150 kg fertilizer plus 6.25 t ha⁻¹ (72 kg N) green manure) and a no N control. Nitrogen application markedly increased the N uptake. Combined use of the two N sources at 200 and 222 kg N ha⁻¹ and of single fertilizer N at 200 kg N ha⁻¹ recorded the maximum N uptake, increased the yield attributes such as number of panicles per unit area, weight per panicle, number of total and filled grains per panicle and test weight. At 200 kg N ha⁻¹ full substitution of N by green manure reduced the grain yield but only partial substitution of N by green manure resulted in almost similar yield as single fertilizer N. Thus 200 kg N ha⁻¹ applied in equal proportions of fertilizer and green manure N can be recommended for medium duration rice cultivars.     

Performance of Agricultural Systems under Contrasting Growing Season Conditions in South-western Quebec

Climate change will alter temperature and rainfall patterns over North American agricultural regions and there will be a need to adapt crop production systems to the altered conditions. A set of field experiments were conducted in south-western Quebec, Canada, with soybean ( Glycine max L.), corn ( Zea mays L.), sorghum ( Sorghum bicolor L.) × sudangrass ( Sorghum sudanense Piper) hybrid and switchgrass ( Panicum virgatum L.) under two tillage and three nitrogen fertility regimes, to study their performance in three successive growing seasons (2001–2003), two of them with unusually warm and dry conditions. The annual crops were established in two tillage systems: conventional and no-till (NT). All crops except soybean were fertilized with three levels of nitrogen: corn – 0, 90 and 180 kg N ha⁻¹, sorghum-sudangrass – 0, 75 and 150 kg N ha⁻¹, switchgrass – 0, 30 and 60 kg N ha⁻¹. The 2001 and 2002 seasons were hotter and drier than the 2003 season, which was the most favourable for crop growth. The capacity of the crops to yield in dry seasons was as follow: switchgrass > sorghum-sudangrass > corn > soybean. The corn and sorghum-sudangrass responses to nitrogen fertilizer were low in 2001 due to the combined effect of dry growing season and coarse soil texture. Soybean did not perform well under NT. Corn yielded better at the highest nitrogen fertilizer rate under NT when the early season was warmer than the normal. Our results show that switchgrass and sorghum-sudangrass could be an option in south-western Quebec if the frequency of hot and dry seasons increase in the future, because of climate change.     

Effect of Gibberellic Acid Spray and Basal Nitrogen and Phosphorus on Productivity and Fatty Acid Composition of Rapeseed-Mustard

Two field experiments were conducted during] 994-95 to study the effect of spray of 10⁻⁵ M GA3 at 40 days after sowing on mustard ( Brassica juncea (L.) Czern & Coss.) cv. Varuna grown with basally applied 0, 40, 80 and 120 kg N ha⁻¹ (Expt. 1) and 0,15, 30 and 45 kg P ha⁻¹ (Expt. 2) on pod number per plant, seeds per pod, 1000 seed weight, seed yield, biological yield, harvest index and fatty acid composition of oil. No significant difference between water and GA3 spray was found when basally applied nitrogen was 0 or 40 kg N ha⁻¹. N₈₀ proved to be the best for yield characteristics. In another experiment on phosphorus, GA₃ and 30 kg P ha⁻¹ individually enhanced the yield, but interaction of GA₃ and P remained non-significant. The fatty acid composition of oil in both experiments was significantly affected only by nitrogen and phosphorus treatments for oleic acid and erucic acid. It was found that return in the form of yield was more for every kg applied fertilizer under GA, spray treatment. The response was more for N fertilizer in comparison to P. GA₃ at a low level of fertilization significantly increased the return from fertilization.     

Performance of Rapeseed-mustard Cultivars under Various Moisture Regimes on the Gangetic Alluvial Plain of West Bengal

A Field trial was conducted during 1988–89 and 1989–90 at Water Management Research Station, Memari. Bidhan Chandra Krishi Viswavidyalaya, Burdwan, to study the effect of three different irrigation regimes, namely rainfed (I₁) (No irrigation), one irrigation (I₂) at flowering and two irrigations (I₃ at flowering and at sihqua formation stages) on the grain yield and water expenses on four different rapeseed-mustard cultivars, namely Pusa Bold, Pusa Baroni, Varuna and DIR 247. The variety DIR 247 recorded maximum grain yield (12.1 qha') followed by Pusa Baroni (11.8 q ha⁻¹). The variety Varuna showed the lowest water use efficiency (48.1 kg ha⁻¹ cm⁻¹) while DIR 247 showed the maximum value of 57.0 kg ha⁻¹ cm⁻¹. The number of irrigations significantly increased the grain yield. Two irrigations, one at flowering and at siliqua formation stage increased grain yield by 28 % over the rainfed plots. During the crop growth period the actual water expenses among the cultivars in any moisture regime were more or less similar. The interaction between varieties and irrigation levels were, however, not significant.     

Effect of Nitrogen and Sulphur Application on Yield and Fatty acid Composition of Mustard (Brassica juncea L.) Oil

The effects of nitrogen and sulphur on the yield and fatty acid composition of mustard ( Brassica juncea L.) oil were studied in a field experiment. Significantly higher grain and oil yields were obtained with N and S application. Applications of nitrogen up to 60 kg ha⁻¹ and sulphur up to 40 kg ha⁻¹ favourably influenced the grain yield. Increasing levels of N decreased the oil content while application of sulphur improved the oil content. The contents of linoleic and linolenic acid were maximum (16.82 and 8.73%, respectively) with 60 kg N along with 40 kg S ha⁻¹. No use of fertilizers led to higher contents of undesirable fatty acids such as palmitic (hypercholesterimic) and erucic (do not have food value) acids.     

Spring Barley Responses to Nitrogen Fertilizer and Ethephon in Regions with a Short Crop Growing Season

Aspects of intensive management practices such as high N fertilization inputs and plant growth regulator use could potentially increase cereal yields in regions with a short crop-growing season and occasionally dry and hot weather. A field experiment was carried out for four years (1987 to 1990) at Agronomy Research Centre of McGill University, Canada to evaluate the response of spring barley ( Hordeum vulgare L.) cv. Cadette, Laurier and Leger to N rates (0, 70 and 140 kg N ha⁻¹) and ethephon (2-chloroethyl phosphonic acid) growth regulator treatment. The application of higher than conventional N level (70 kg N ha⁻¹) did not increase barley yields under dry weather conditions and when the soil N resources were high. The high levels of N did increase the grain crude protein concentration by 2 to 10 g kg⁻¹, as did ethephon treatment. The feed quality of spring barley was improved. Ethephon treatment reduced grain yield due to a severe reduction in the number of grains spike⁻¹, and/or 1000-grain weight, although the number of spikes m⁻² was increased. Thus, the overall effect of ethephon treatment on yield was inconsistent and was influenced to a large extent by the prevailing weather conditions.     

Nitrogen Nutrition of Potato Cultivars Differing in Maturity

In potato, dry matter (DM) production and partitioning between plant organs and N accumulation are affected by N application; however, since cultivars differ in these processes, N fertilization must be adjusted to each cultivar. This paper studies the response of potato cultivars differing in maturity to N fertilization in the south-east of the Buenos Aires Province (37°45'S, 58°18'W) in two growing seasons. Treatments combined four N doses (0–180 kg ha⁻¹) and four cultivars: Jaerla (early), Spunta (mid-early), Mailén INTA (medium late) and Huinkul MAG (late). DM and N content were measured in leaves, stems and tubers throughout the growing season and intercepted photosynthetically active radiation was regularly assessed. There was an increase in tuber yield up to intermediate N doses (60 kg ha⁻¹ in 1990 and 120 kg ha⁻¹ in 1991). Tuber yield was similar for Spunta and Huinkul MAG. There was no interaction between cultivar and N fertilization for tuber dry matter yield. DM partitioning to leaves and tubers during the growing season differed among cultivars, but N availability affected partitioning similarly for all cultivars. Jaerla had a high and Huinkul MAG had a low radiation use efficiency between plant emergence and the beginning of tuber formation. Jaerla, Spunta and Mailén INTA reached maximum N content in foliage at ≈60 days after emergence and Huinkul MAG 20 days later. Total N content at maturity varied between 120 and 250 kg ha⁻¹ and was affected by cultivar and N dose. The results will help to improve N fertilization recommendations and management practices as related to each cultivar under the environmental conditions of this region.     

Influence of Variable Amounts of Irrigation Water and Nitrogen Fertilizer on Growth, Yield and Water Use of Grain Sorghum

Sorghum hybrid CSH-6 was grown in fields in Delhi, India between July–November 1986 in order to study the effect of nitrogen nutrition and irrigation on dry matter accumulation, grain yield and water use. The treatments included 40 Kg Nha⁻¹ combined with two irrigations (30 DAS, 60 DAS), one irrigation (60 DAS) and no irrigation respectively. Rainfall during the crop season was only 17 cm. The unirrigated plants were considerably water stressed and exhibited very low leaf water potential, less leaf area, delayed anthesis, longer crop duration but shorter grain filling duration. The ears showed sterility and yield was only 0.41 t ha⁻¹ without nitrogen fertilization. Addition of nitrogen fertilizer had no significant effect on yield in unirrigated plants. A single irrigation 60 DAS increased yield due to increase in both grain number and grain weight per ear in fertilized and unfertilized crop respectively. Two irrigations in the unfertilized crop increased the yield to 2.2 t ha⁻¹ while similar treatment in the fertilized crop did not increase the yield significantly. Irrigation increased the WUE for grain yield. The results indicate that nitrogen stress and water stress reduced grain yield primarily through grain number rather than grain weight. Irrigation relieved both water stress and nutrient stress. Nitrogen nutrition was not beneficial under severe water stress conditions but was considerably helpful under mild stress. Biomass, grain yield and harvest index show significant correlation with preanthesis water use.     

Yields and Land-Use Efficiency of Maize-Cowpea Crop Rotation in Comparison to Mixed and Monocropping on an Alfisol in Northern Ghana

Results reported in the literature with regard to productivity of intercropping systems in comparison to sole cropping are very inconsistent. A field experiment was therefore conducted in the northern part of the Guinea Savanna in Ghana to compare the productivity of maize/cowpea mixed cropping, maize/cowpea relay intercropping with maize/cowpea rotation and maize monocropping over a 4-year period. The treatments included two levels of nitrogen (0 and 80 kg of N ha⁻¹ y ⁻¹ as urea) and two levels of phosphorus application (0 and 60 kg of P ha⁻¹ y⁻¹ as Volta phosphate rock). At all levels of N and P application, maize yields of the intercropping systems, especially of maize/cowpea mixed cropping, were significantly lower than in sole cropping. Highest maize yields were obtained in maize/cowpea rotation, which in contrast to the other cropping systems did not show any reductions in yields over years. Cowpea yields were generally less affected by the cropping system, but were notably depressed when cowpea was relay-intercropped with maize. In treatments without fertilizer application (N and P) Land Equivalent Ratios (LER) and Area x Time Equivalency Ratios (ATER) generally indicated lower productivity of the intercropping systems as compared to sole cropping, with the maize/cowpea rotation showing the highest productivity. Conversely, fertilizer application resulted in higher productivity of the intercropping systems over the 4-year period. Productivity on the basis of ATER was generally lowest in maize/cowpea relay-intercropping as a consequence of the long time of land occupation. All of the parameters indicate low productivity of maize monocropping, clearly demonstrating that crop sequence as well as fertilizer application must be considered as important for maintaining high production levels at this site.