Sustainable yield trends of irrigated maize and wheat in a long-term experiment on a loamy sand in semi-arid India

Long-term field experiments play an important role in understanding the complex interactions of plants, soils, climate and management and their effects on sustainable crop production. A long-term fertilizer experiment with maize-wheat-cowpea (fodder) is in progress since 1971 at Punjab Agricultural University farm Ludhiana, India. The experimental result for the first 21 years showed that application of N alone or in combination with P did not produce as much maize and wheat grains as the application of N, P and K together. Eight years after the start of the experiment, the optimal levels of N, P and K application (100% NPK) were unable to sustain the similar (maize) yield level as before because of Zn deficiency. Whereas in FYM amended plots the Zn deficiency did not appear and the higher crop yields could be sustained. The chemical control of weeds could not sustain the maize productivity at the same level as the manual removal of weeds. It was concluded that the high level of crop production can be sustained with the application of N, P and K under intensive cropping system provided deficiency of any of the micronutrient does not crop up. The deficiency of Zn is most likely to occur in semi-arid light textured alluvial soils under intensive cropping without the addition of farm yard manure/organic manures. In maize based cropping systems, manual control of weeds may be preferred to the chemical one. Addition of FYM in conjunction with 100% NPK is most beneficial both from bio-physical and economic point of view.     

Penicillium bilaji and phosphorus fertilization effects on the growth,development, yield and common root rot severity of spring wheat

A strain ofPenicillium bilaji Chalabuda (PB) has recently been commercially released as a seed inoculant to increase phosphorus (P) uptake by wheat (Triticum aestivum L.). The purpose of this study was to compare the effects of drill applied P (15 kg P ha^–1) with PB seed inoculation on early growth, development, P uptake, and grain yield of Stoa spring wheat at four sites in North Dakota.Fertilization with P consistently enhanced early season growth, main stem development, tillering and P uptake. Seed inoculation with PB had little or no effect on these traits. Phosphorus fertilization tended to increase common root rot severity (CRR, incited byCochliobolus sativus (Ito & Kurib) Drechs.), while PB inoculation had no effect. Grain yields were significantly increased by P fertilization at one location. Inoculation with PB also increased grain yield at this location. The reason why PB inoculation increased yield at this location is not evident, as plant growth and P uptake were not enhanced earlier in the season. Averaged across all four sites, PB inoculation increased wheat yields 66 kg ha^–1, which is similar to averaged yield responses reported from the Prairie Provinces of Canada.     

The effect of fertilizer placement on nitrogen uptake and yield of wheat and maize in Chinese loess soils

Field trials were carried out to study the fate of¹⁵N-labelled urea applied to summer maize and winter wheat in loess soils in Shaanxi Province, north-west China. In the maize experiment, nitrogen was applied at rates of 0 or 210 kg N ha^–1, either as a surface application, mixed uniformly with the top 0.15 m of soil, or placed in holes 0.1 m deep adjacent to each plant and then covered with soil. In the wheat experiment, nitrogen was applied at rates of 0, 75 or 150 kg N ha^–1, either to the surface, or incorporated by mixing with the top 0.15 m, or placed in a band at 0.15 m depth. Measurements were made of crop N uptake, residual fertilizer N and soil mineral N. The total above-ground dry matter yield of maize varied between 7.6 and 11.9 t ha^–1. The crop recovery of fertilizer N following point placement was 25% of that applied, which was higher than that from the surface application (18%) or incorporation by mixing (18%). The total grain yield of wheat varied between 4.3 and 4.7 t ha^–1. In the surface applications, the recovery of fertilizer-derived nitrogen (25%) was considerably lower than that from the mixing treatments and banded placements (33 and 36%). The fertilizer N application rate had a significant effect on grain and total dry matter yield, as well as on total N uptake and grain N contents. The main mechanism for loss of N appeared to be by ammonia volatilization, rather than leaching. High mineral N concentrations remained in the soil at harvest, following both crops, demonstrating a potential for significant reductions in N application rates without associated loss in yield.     

The effect of zinc fertilizer on take-all and the grain yield of wheat grown on zinc-deficient soils of the Esperance region,Western Australia

Wheat plants were grown in field experiments with five levels of zinc (Zn) fertilizer applied to plots in 1983. The plots were continuously cropped with wheat to allow the build up ofGaeumannomyces graminis var.tritici (Ggt). For experiments 1 and 2, there were high levels of Ggt in the second and third years while for experiment 3 there were high levels of Ggt incidence in the third and fourth year of continuous cropping. The Zn status of the wheat plants, grain yield, and the incidence and severity of take-all were measured for every experiment each year.The Zn-deficient wheat plants were more severely infected by Ggt. However, increasing the Zn supply beyond that required for maximum grain yield had no further effects on decreasing the severity of take-all. The Zn concentration in the youngest emerged blade (YEB) suggested that the Zn status of the wheat plant ranged from severely Zn-deficient through marginal deficiency to sufficiency.The Zn-deficient wheat plant was more susceptible to Ggt infection than Zn-adequate plants. The severity of take-all in the final year was still high in Zn-adequate plants, suggesting high levels of applied Zn (11.2 kg Zn/ha in 1983) had no fungistatic effect on Ggt.     

The effect of various phosphorus fertilizers on yields,phosphorus uptake by plants and conversion of phosphorus fertilizers in long-term experiments on different soils

Long-term experiments have been undertaken to investigate the effects of various types of phosphorus fertilizers on yields, phosphorus uptake and fertilizer conversion in the soil. Optimum effects were obtained from water-soluble phosphate, whereas finely ground soft rock phosphate had little effect even with large amounts of phosphorus fertilizers and with a pH value of the soil of around 5.4. Partially decomposed and sintered phosphates performed well, as did NPK fertilizers (100% water soluble) and Thomas phosphate. The addition of large amounts of phosphorus fertilizers (to cereals, 26.4 kg/ha, to other crops 44 kg/ha) led to yields being increased by 7% and phosphorus extraction being increased by 11%. Smaller amounts of phosphorus fertilizers (13.2 and 17.6 kg/ha) did not have this effect. Increases in the amount of double-lactate-soluble phosphorus in the soil depended on the level of fertilization and did not differ significantly according to the type of phosphorus fertilizer used.     

Response of wheat to nitrogen fertilization,a data set to validate simulation models for nitrogen dynamics in crop and soil

A data set originating from winter wheat experiments at three locations during two years is described. The purpose is to provide sufficient data for testing simulation models for soil nitrogen dynamics, crop growth and nitrogen uptake. Each experiment comprised three different nitrogen treatments, and observations were made at intervals of two or three weeks. The observations included measurements of soil mineral nitrogen content, soil water content, groundwater table, dry matter production and dry matter distribution, nitrogen uptake, nitrogen distribution and root length density.     

Relationship between soil physical and chemical characteristics and ear-leaf concentration of P,K, Mg,Zn, Fe,Cu, Mn and relative yield of maize in soils derived from sedimentary rocks of South-Western Nigeria

In a four-season field experiment conducted in 18 locations covering two different ecological zones of the sedimentary forest soils of South-Western Nigeria, relationships were established by simple correlation between the ear-leaf content of P, K, Mg, Zn, Fe, Cu, Mn, relative yield of maize (RY), soil physical characteristics and soil nutrient status. Soil pH was strongly related to the relative yield, soil clay, available P, exchangeable Ca, K, Zn, and Mn in soils, P and Cu concentration in the ear-leaf.Organic matter did not appear to play a very significant role in nutrient supply or relate to nutrient element concentration in the ear-leaf and relative yield in soils that are relatively low in soil organic matter.Nitrogen was not determined. Phosphorus among all the elements determined seemed to have a high significant effect on Ca, K, Zn, Mn and RY. However, the effect on RY was negative. Manganese in both soil and ear-leaf had the highest negative significant relationship with yield in the zone.The multiple regression analysis indicated a relationship meaning that the soil physical and chemical properties and ear-leaf content of the elements P, K, Mg, Zn, Fe, Cu, Mn are important to maize cultivation in this zone. Hence consideration of a combination of soils and plant factors are essential before meaningful fertilizer recommendation can be made for maize in the zone under study.     

The current and residual value of superphosphate for lupins grown in rotation with oats and wheat on a deep sandy soil

In a field experiment on a deep pale-yellow sand in a 600 mm per annum rainfall Mediterranean environment of south-western Australia, six levels of phosphorus (P) as superphosphate (O up to 546 kg P ha^–1) were applied once only, to the soil surface, before sowing lupins (Lupinus angustifolius). The lupins were grown in a continuous arable cropping rotation with, in successive years, oats (Avena sativa), wheat (Triticum aestivum), lupins. Five such rotations were started in the experiment from 1985 to 1989. The experiment continued until the end of 1990.The relationship between lupin seed (grain) yields and the level of P applied was measured in the year of P application for five successive years (1985 to 1989). The relationship had the same general form but it varied between years, largely due to different maximum yields (yield plateaux) in each year.The residual value of superphosphate applied three years previously was measured for lupins on two occasions (1988 and 1989) relative to superphosphate applied in the current year. The residual values was different in the two years. The superphosphate applied three years previously was about 30% as effective as freshly applied superphosphate in 1988, and 12% as effective in 1989.At each harvest, the relationship between grain yield and the P concentration in the grain differed for different species. However, for each species at each harvest, the relationship was similar regardless of when the P was applied in the previous years. Thus each species had the same internal efficiency of P use curve, and yields varied only with P concentration in tissue.Bicarbonate-extractable soil P was determined on soil samples taken in mid-July of 1989 and 1990. These soil test values were related to grain yields at harvest. The relationship between yield and soil test values had the same general form but varied for different species within years and for each species between years. It also varied for each species within years depending on the year the P was applied.     

Response of soil phosphorus content,growth and yield of wheat to long-term phosphorus fertilization in a conventional cropping system

The effect of annual banding of superphosphate (0–45 kg P ha⁻¹) on soil phosphorus (P) content, growth, and yield of wheat was investigated from 1982 to 1998 in a major rainfed wheat production area of South Africa. Conventional tillage practices in a wheat monoculture cropping system were followed under summer rainfall conditions. The responses of wheat growth to fertilizer P application were evident during early and late tillering growth stages, with decreased responses towards maturity. Although average yields varied between cropping seasons (0.881 to 3.261 t ha⁻¹) due to climatic conditions, significant exponential response patterns between yield and fertilizer P applications existed. Optimum yields were achieved with P applications of 10 to 15 kg P ha⁻¹. The recovery of fertilizer P in the grain decreased with increasing P applications. Results of soil P analyses and calculated P balance indicated a more rapid increase in soil P content with application of fertilizer P at levels above 20 kg P ha⁻¹, with gradual increases occurring at lower levels. This revised version was published online in August 2006 with corrections to the Cover Date.