Long-term Fertilization Trial Research Articles

The long term fate of copper fertilizer applied to a lateritic sandy soil in Western Australia

A soil copper fractionation was carried out on soils sampled from plots in a long-term copper fertilizer trial on a lateritic sandy soil in Western Australia. At copper application rates up to 8.25 kg copper sulphate ha-1, a high proportion of the applied copper was initially associated with the soil organic matter. During the course of the trial (20 years), a substantial proportion of this copper became redistributed to a residual soil fraction, i.e. the residue remaining after extractions to remove organic matter and iron oxides. However, significant redistribution of copper with time was not detected in plots with a higher rate of copper application (19.25 kg copper sulphate ha-1). The change in distribution of copper at the lower copper application rates appeared to be only partly responsible for a corresponding decrease observed in EDTA-extractable soil copper during the trial. The changes with time in the nature of fertilizer copper applied to this soil are considered to be responsible for the previously observed decline in plant availability of such copper.

Yield response of maize to fertilizers and manure under different agro-ecological conditions in Kenya

In Kenya, 70 long-term fertilizer trials were established in which the response of the major annual crops to nitrogen, phosphorus and farmyard manure was tested. As the sites all represent well-defined agro-ecological units, the trial results can be used as a basis for area-specific fertilizer recommendations. Results of 4 years (1987–1990) of fertilizer and manure application to maize at three sites were evaluated. The selected sites are at altitudes of 2020 m (Nitisol), 1160 m (Phaeozem), and 130 m (Alisol). All the sites are in maize-growing environments, but farmers use different hybrids. Analysis of variance revealed that maize on the Nitisol responded vigorously to phosphorus and manure, with even a significant interaction. On the Phaeozem, it was solely nitrogen that limited yields, and on the Alisol there was a response to both nitrogen and phosphorus. At a relatively low level of fertilizer input (Sh. 825–1125), farmers can, in 3 out 4 years, earn an extra Sh. 3000 from the Nitisol (value/cost 4.5), Sh. 4000 from the Phaeozem (value/cost 4.2), but only Sh. 425 from the Alisol (value/cost 1.5). The study clearly shows the need to (i) recommend fertilizers according to the agro-ecological diversity of agricultural land, and (ii) support systems of integrated nutrient management, particularly in areas of low soil fertility, where the farmer has too few economic incentives to rely solely on mineral fertilizers.

Long-term effect of cassava cultivation on soil productivity

Cassava ( Manihot esculenta Crantz) is usually grown by poor farmers in the tropics with a minimum of inputs. Continuous production under these conditions can lead to soil nutrient depletion. On sloping land, cassava cultivation can also cause severe erosion if the crop is not properly managed. This paper reviews the literature to show that cassava does extract large amounts of nutrients, especially potassium (K), from the soil. However, when nutrient extraction is calculated on the basis of per unit quantity dry-matter produced, cassava extracts much less N and P than, and similar amounts of K to, most other crops. Long-term fertility trials indicate that, without adequate K fertilization, cassava yields eventually decline due to K depletion, except in those soils containing large amounts of K-bearing minerals. While cassava production may result in severe erosion when grown on steep slopes, simple agronomic practices can usually maintain soil losses within acceptable levels. The effect different cultivation practices on erosion and yield varies from location to location, and the most appropriate practices can be identified through simple erosion-control trials on farmers' fields. Thus, productivity of continuously grown cassava fields can be maintained through judicious use of fertilizers and soil management practices that control erosion.

Short-and long-term fertility trials in Colombia to determine the nutrient requirements of cassava

One-year simple NPK trials were conducted in 22 locations in four regions of Colombia to determine the response of cassava (Manihot esculenta Crantz) to N, P and K and to relate this response to the available P and K contents of the soil, as well as to the N, P, and K concentrations in youngest fully expanded leaf (YFEL) blades sampled at 3–5 months after planting. It was found that cassava responded mainly to P applications in the low-P soils of the Eastern Plains and of Cauca Department, to K applications only in the Eastern Plains and to N applications principally in the sandy, low-OM soils of the Atlantic Coast. By relating the relative response to P and K to the available P and exchangeable K content of the soil, respectively, critical levels of 4 mg P/kg and 0.17 me K/100 g (both extracted with Bray II) were determined. Similarly, critical levels of 5.6% N, 0.41% P and 1.42% K were determined in YFEL-blades.

CHANGES IN YIELD RESPONSE TO MAJOR NUTRIENTS AND IN SOIL FERTILITY UNDER INTENSIVE RICE CROPPING

Nutrient balance is a critical factor in maximizing grain yield of a single crop and in crop intensification. This paper summarizes data on rice yield and soil fertility parameters from long-term fertility trials, under a rice-rice cropping system, conducted at four sites in the Philippines: three rice experiment stations, namely, Bicol (Pili clay: Typic Pelludert), Maligaya (Maligaya silty clay: Vertic Tropaquept), and Visayas (Santa Rita clay: Typic Pelludert) from 1968 to 1986; and the IRRI farm (Maahas clay: Andaqueptic Haplaquoll) from 1964 to 1986. Large responses to complete NPK fertilizer were observed at all four sites, but response to individual nutrients (N, P, or K) differed greatly among sites. N-use efficieny did not change over time at IRRI and Bicol, but decreased substantially over time at Maligaya and Visayas. P-use efficiency, however, increased drastically over time both at Maligaya and Visayas, more so after 10 yr of cropping, but no change in P response over time was observed at Bicol. At IRRI, there were no appreciable responses to P or K throughout the 23-yr period; at the other sites where there were appreciable responses to P and K, interactions between P and K were large, i.e., response to P was larger when K was applied than when no K was applied, and response to K was larger when P was applied than when no P was applied. The difference in response between the dry and the wet seasons was more pronounced in responses to P and K than with response to N. Yields from organic + inorganic NPK fertilizer (tested only at IRRI) did not differ from those from NPK inorganic fertilizer alone at any time in the 23-yr period. Under intensive rice-rice croppings, the soil pH decreased, and the total N and organic matter content increased, with successive applications of one or more nutrients over time. Extractable P values in P-fertilized plots were higher than those in plots that did not receive P over time. The exchangeable K values decreased with successive application of P and increased with successive application of K, over time. The effects of successive application of fertilizers on CEC and exchangeable Ca in the soil were not consistent.

GROWTH AND YIELD OF WHITE BEAN (Phaseolus vulgaris L.) IN RESPONSE TO NITROGEN, PHOSPHORUS AND POTASSIUM FERTILIZER AND TO INOCULATION WITH Rhizobium

Two white bean (Phaseolus vulgaris L.) cultivars grown for 2 yr on test plots of a long-term fertilizer trial showed a significant response to nitrate in the first year and in the 2 yr combined but not in the second year on its own. Yield in the second year was about half of that in the first year, possibly because of water stress. Bean yield was lowest in the zero nitrate, about equally high for 112 and 224 kg N ha−1, but somewhat lower at 336 kg N ha−1. Annual application of potassium and phosphorus (compared to no application for 12 yr) did not affect bean yield, but increased plant dry weight after 24 d in 1984 and the 2 yr combined, after 38 d in 1984 and after 52 d in 1983 and also increased the number of days to maturity. Nitrate effects on the dry weights of samples taken during the growing season were similar to those for bean yield. Acetylene reduction rates (first year) and nodule weights were highest in zero N and declined to very low values at 336 kg N ha−1. Acetylene reduction rate per plant reached a maximum value early in the season and declined to low values before bean filling was complete. Rhizobium inoculation had no discernible effects on dry weights or yield, but a small significant effect on days to maturity. We conclude that these white bean cultivars are unable to fix sufficient nitrogen to produce maximum yield.Key words: Field bean, Phaseolus vulgaris, nitrogen, Rhizobium

Effect of a wide range of nitrogen applications on herbage nitrate content in long-term fertilizer trials on all-grass swards

In three long-term nitrogen fertilization experiments with total applications of up to 1120 kg N per ha per year and cutting at a DM yield of 2 to 2.5 t per ha, the herbage nitrate content of all-grass swards was studied for each cut. At applications of 60 kg N per ha per cut, with a maximum of 360 kg N per ha per year, there was little or no increase in nitrate content. At applications of 80 kg N per ha per cut, totalling 400–560 kg N per ha per year, 3% of the samples had nitrate contents higher than 0.75% N03. At applications of 120 and 160 kg N per ha per cut, totalling 600–1120 kg N per ha per year, 61 and 67% of the samples exceeded 0.75% N03, respectively. The excess nitrate did not occur in the spring cuts, but for the most part in the summer cuts and seldom in the autumn cuts. This may explained by a positive relationship between temperature and herbage nitrate content, under favourable moisture conditions. In warm but dry periods there was no relationship and nitrate contents were low.

Students need to critically analyze what they read

The need for students to critically analyze what they read is clearly apparent. In reviewing literature in preparation to teach a course in organic agriculture, it became evident that one needs to carefully check references and statistics cited in the articles. Consequently I developed a handout for the students to stress this need. The handout starts with an excerpt from an article and traces a series of references to show that statistics had been misinterpreted and resulted in an erroneous conclusion by the most recent author. The erroneous statement claimed that more and more chemical fertilizer was required each year to sustain the same yield. The supporting reference said essentially the same thing but cited a third source. This earliest source cited statistics to show that more N was used per unit of corn yield in 1968 than in 1949. The author of the primary information did not state that more N was required to produce a given yield per unit area in 1968 than in 1949. The handout I developed illustrates how the biological principles of a decreasing rate of yield response to applied N results in low efficiency of N at high application rates. The use of higher rates of N in 1968 resulted in lower overall N efficiency, and thus more N was required to produce a unit yield of corn. The long-term fertility trials at Rothamsted illustrate that more fertilizer is not needed each year to sustain yields.

EFfect of phosphorus on N2-fixation as measured by the field acetylene reduction technique in Thailand long-term fertility plots

Abstract An in situ acetylene reduction technique was applied to wetland fields in Thailand to assess the relative contributions of N2-fixation associated with rice, and algal N2-fixation. Non-fertilized and PK-fertilized plots were used in long-term fertility trials at three sites with high (Chainat), medium (Supanburi), and low (Klong-luang, acid sulfate soil) soil fertilities. Assays were made at the maximum tillering, heading, and maturing stages during four continuous cropping seasons spanning 2 years. Since the regression coefficients for the logarithm of variance to the logarithm of the mean were close to 2.0, the log normal distribution of the acetylene reduction activity variables could be predicted, and the variables were subjected to logarithmic transformation for statistical calculation. Additions of PK fertilizer affected the rice yields and N2-fixation associated with rice at Supanburi and Klong-luang, but not those at Chainat. The PK fertilizer affected the algal N2-fixation at Chainat and ...

Mineral nutrition and reduction processes in the rhizosphere of rice

The influence of nitrogen, phosphorus, and potassium on the reduction processes in the rhizosphere of rice grown in solution culture and of rice under lowland conditions was studied. In solution culture the redox potential in the complete nutrient solution was highest, indicating that fully nourished roots have the highest oxidizing power. When the supply of only one element was interrupted, the lack of potassium in the nutrient solution caused the greatest decline in redox potential. Redox potential was further decreased when, besides nitrogen, either phosphorus or potassium was discontinued. Simultaneous deficiencies of nitrogen and potassium lowered redox potential even more severely than did deficiency of all three elements. A long-term nitrogen fertilizer trial under lowland conditions, however, revealed that an abundant supply of nitrogen can decrease redox potential. Redox potential was higher in the soil near plants than in the soil away from plants. In solution culture, at low Eh levels, the increase in iron reducing power of the solution was correlated with the decrease in redox potential. The total number of bacteria and iron reducing bacteria increased almost parallel to the decrease in redox potential and increase in iron reducing power. These relationships show that the nutritional status of the rice plant essentially influences bacterial activity and, thus, oxidation-reduction conditions around the roots. Since sufficient potassium nutrition seems important in maintaining the oxidising power of rice roots, root growth in a potassium deficient soil with K application was compared with root growth without K application. Without potassium the fine lateral roots far from the root base showed black coloration due to ferrous sulfide, indicating a loss of oxidising power. With increasing potassium supply, this phenomenon disappeared and the iron content of the rice plants decreased. re]19751208

Changes in soil chemical properties in a long-term fertilizer trial in a non-irrigated vineyard

Changes in soil properties in a long-term factorial experiment with nitrogen, phosphorus, and potassium fertilizer at the Nuriootpa Viticultural Research Station in South Australia were measured after 23 years of application. The measurements were related to vine yield responses reported earlier. Phosphorus, broadcast as superphosphate, gave excessively high available phosphorus levels in the top 6 in, of soil, but yield responses were delayed for 8 years until the slow-moving phosphorus reached the 6–12 in. layer where the feeder roots occurred. Broadcasting superphosphate was a wasteful and inefficient means of applying phosphorus in this environment. About three-quarters of the phosphorus applied could be measured in the top foot of soil. Nitrogen applied as sulphate of ammonia reduced pH significantly in the top 18 in. of soil, with the biggest reduction of 1.5 units to pH 5.0 in the 6–12 in. layer. As this acidity developed it probably caused the depression in vine vigour and yield. Potassium levels were high and not limiting in the unfertilized soils. The relation between nutrients supplied in the fertilizers and nutrients removed in the grapes is discussed.

Leaf analysis in the assessment of nutritional status of apple trees

Abstract Apple leaf sampies from a long-term fertiliser trial have been analysed to study the variation in content of nitrogen, phosphorus, potassium, and magnesium. Fertiliser treatment had a marked effect on content of each element; differences within and between seasons were also apparent. Critical nutrient levels for apple foliage, suggested elsewhere, would seem to be largely applicable to New Zealand trees.

Chemical changes in an irrigated soil during 28 years of differential fertilization

Abstract does not appear. First page follows. Introduction One of the most extensive long-term fertility trials on irrigated soils in a semiarid region is the fertilizer experiment with citrus being conducted at Riverside. The purposes of the experiment were to study the effects of a variety of fertility levels and treatments on yield, growth, and behavior of trees, to measure the cumulative and secondary effects of fertilizers on the trees, and to study the effects of fertilizers, soil amendments, and irrigation on properties of the soil. The purpose of this paper is to report changes in the chemical properties of the soil that have resulted from irrigation and differential fertilization. Description of the experiment Washington Navel oranges on sweet orange rootstocks were planted for this experiment in 1917. The land had been previously dry-farmed but had not been fertilized or irrigated. During the first ten years of the growth of the trees fertilizers were not used. During this period winter covercrops of yellow bitter clover or of purple vetch were grown annually, and during the first six years, summer covercrops of cowpeas were grown. The winter cover-crops used since 1927 have been dominantly vetch with barley. In 1927, differential treatments of the plots were begun. (Parker and Batchelor (1932))6 described the method of distributing the plots to the various treatments. Each plot consisted of a row of eight Washington Navel