K. Sammi Reddy

Yield sustainability and phosphorus utilization in soybean–wheat system on Vertisols in response to integrated use of manure and fertilizer phosphorus

Abstract Low native soil phosphorus (P) availability coupled with poor utilization efficiency of added P is a major constraint limiting the productivity of soybean–wheat system on Vertisols in Indian semi-arid tropics. The use of fertilizer P is limited by its high cost, while organic inputs generally cannot provide sufficient P for optimum crop growth due to their low P concentration. We, therefore, evaluated in a 5-year field experiment (1992–1997) the effects of integrated use of manure and fertilizer P on crop yield sustainability, P utilization and soil P fertility under soybean–wheat system on a Typic Haplustert. The treatments consisted four rates each of manure (applied only to soybean) and fertilizer P (applied to both soybean and wheat) arranged in a split-plot design with four replications. Both soybean and wheat crops responded significantly to the application of manure and fertilizer P. For the same level of P input, the yield increases were greater with manure P than with fertilizer P. Further, integrated use of fertilizer P and manure was better than their sole application in increasing and sustaining the productivity of soybean–wheat system. The P uptake by the crops increased with increasing rates of manure and fertilizer P and was relatively larger in soybean than in wheat. The per cent phosphorus recovery by the crops from fertilizer P decreased with increasing fertilizer P rate, while it was improved in the presence of manure. Though the extent of fertilizer P recovery was more or less similar in both the crops, soybean was more efficient than wheat in extracting the soil and manure P. The available P status of the soil showed a significant build-up during successive cropping seasons due to fertilizer P and the increase was strikingly greater when fertilizer P was applied in combination with manure. The integrated use of manure and fertilizer P is a promising strategy to improve soil P fertility status and to obtain higher and sustained productivity of the soybean-wheat cropping system on Vertisols of the semi-arid tropics.

Malachite green method compared to ascorbic acid for estimating small amounts of phosphorus in water, 0.01M calcium chloride, and Olsen soil extracts

Abstract Malachite green method has been evaluated for estimating minute quantities of phosphorus (P) in water, 0.01M calcium chloride (CaCl2), and Olsen [sodium bicarbonate (NaHCO3)] extracts often soils of varying properties. The precision and accuracy of the malachite green method was better than that of the ascorbic acid method to estimate P in these three extracts. The recovery of added P ranged from 95.3–99.3% in water, 96–100% in 0.01M CaCl2, and 96.7–100% in Olsen extracts. The ascorbic acid method underestimated the amounts of 0.01M CaCl2‐P and its precision was also lower than the malachite green method. It is possible to predict the P concentration in the three extracts equal to malachite green method from the ascorbic acid P values by using regression equations.

Changes in organic and inorganic sulfur fractions and S mineralisation in a Typic Haplustert after long-term cropping with different fertiliser and organic manure inputs

Changes in the status of organic and inorganic pools of soil sulfur (S), total nitrogen (N), and organic carbon, and their interrelationships and S mineralisation were examined on a Typic Haplustert soil after a 27-year long-term cropping. The results indicated that NPK(+S) applied for 27 years at 50%, 100%, and 150% of optimum recommended rates and 100% NPK(+S) with farmyard manure (FYM) increased the organic C and total N status of soil compared with the control and the initial status of the soil. Intensive cropping with continuous use of 100% NPK without S resulted in depletion of total, organic, and inorganic S concentrations by 18.13%, 17.80%, and 21.72%, respectively, over the control, while the status of total, organic and inorganic S improved in plots that received graded rates of S with NPK and NPK plus FYM. Intensive cropping with continuous use of S-free NPK fertiliser (100% NPK-S) resulted in the widest C: N: S ratio in the soil. NaHCO 3 -extractable total, inorganic, and organic S fractions and NaOH-extractable total and inorganic S fractions were found to be better indices of soil S mineralisation than CaCl 2 -extractable inorganic S. Cumulative amounts of S mineralised during a 14-week incubation period varied between 2.3 and 21.3 mg S/kg soil and increased with an increase in the rates of S applied, along with NPK fertilisers. Incorporation of FYM with 100% NPK(+S) resulted in greater cumulative mineralised S over 100% NPK(+S) alone. The cumulative mineralised S showed a quadratic relationship with the duration of incubation in all the treatments.

How Important is the Quality of Organic Amendments in Relation to Mineral N Availability in Soils

SummaryWastes generated from municipal and agricultural activities have the tremendous potential for application in agriculture as a source of nutrients and as amendments to improve soil organic matter (SOM). A decline in SOM can represent a serious threat to soil fertility and quality. Nitrogen (N) mineralization from organic amendments is important for understanding the N dynamics in terrestrial ecosystems. In this review, quality of the amendments such as C/N ration, N content, and biochemical compositions, etc. are discussed. Since, C/N ratio cannot explain all differences in N mineralization; emphasis has been laid on characterizing different compounds in organic amendments that govern the mineralization process. The importance of simulation models has also been described in modeling N mineralization from some complex materials like compost, animal manures and farmyard manures. These complex simulation models once modified according to the quality of the organic amendments can simulate N mineralization and thus, they can be used for simulating N dynamics in terrestrial eco-systems.

Transformation of fertilizer P in a Vertisol amended with farmyard manure

Availability, fixation, and transformation of added P were studied in a 16-week incubation experiment with a Vertisol amended with farmyard manure in pots with 500 g soil each. P availability, as measured by Olsen P, decreased for up to 8 weeks with various rates of added P, when no manure was applied. In the presence of farmyard manure, P availability decreased during the first 6 weeks and then showed a considerable increase from the 8th week onwards. P fixation increased for up to 8 weeks with the rates of P in the absence of manure. With manure application, P fixation increased only during the first 6 weeks and thereafter decreased continuously. Thus the presence of farmyard manure shortened the period of P fixation and promoted its availability. After 16 weeks of incubation, when manure and fertilizer P were applied together, P was transformed into labile organic (NaHCO3−P), moderately labile organic P (NaOH-P), and calcium-bound inorganic P (HCl-P). When manure was not applied. P accumulated predominantly as labile inorganic (NaHCO3−P), moderately labile inorganic (NaOH-P), and inorganic HCl-P. The application of farmyard manure enriched long-term P fertility through NaHCO3−P and NaOH−P and a shortterm P supply as HCl-P. All fractions except inorganic NaOH-P showed good relationships with Olsen P.

Porosity Distribution, Surface Area, and Morphology of Synthetic Potassium Zeolites: A SEM and N2 Adsorption Study

The morphology of a synthetic zeolite (1717-nm particle-size grains; pore width 10–15 nm) as well as its surface area and mesoporosity is described. Morphology investigated by field emission scanning electron microscopy has shown cuboid crystals. The full adsorption–desorption isotherms for N2 gas measured volumetrically at 77 °K have shown type IV isotherm with type H3 hysteresis loops. To study the reliable pore-size distribution, both adsorption and desorption, curves were used by fitting the data to several well-known adsorption models: Brunauer–Emmett–Teller (BET), Barret, Joyner, and Halenda (BJH), Dollimore and Heal (D-H), Horvath–Kawazoe, and the density functional theory (DFT).

Nanostructured Natural Zeolite: Surface Area, Meso-pore and Volume Distribution, and Morphology

Analysis of meso-porosity, morphology, and textural characteristics of a commercial Indian zeolite was done experimentally using a nitrogen (N2) adsorption isotherm. Scanning electron microscope (SEM) morphology has been described for the nanostructured Indian zeolite (550-nm particle-size grains; pore width 19–22 nm) as well as its surface area and meso-porosity. The detailed surface area, pore volume, and pore size were determined from the adsorption–desorption isotherms of nitrogen measured volumetrically at 77K. To study the reliable pore-size distribution (PSD) both adsorption and desorption curves were used by fitting the data to several well-known adsorption models: Bruaner–Emmett–Teller (BET) model, Barret, Joyner and Halenda (BJH) model, Dollimore and Heal (D-H) model, Horvath–Kawazoe model, and the density functional theory (DFT) model. The sample did not contain any micropores as evident from BJH cumulative pore volume. Further morphology investigated by field emission scanning electron microscopy has shown the tubular crystals.

Effects of Long-Term Fertilizer Application and Rainfall Distribution on Cotton Productivity, Profitability, and Soil Fertility in a Semi-arid Vertisol

Long-term fertilizer experiments were conducted on cotton (Gossypium hirsutum) for 21 years with eight fertilizer treatments in a fixed site during 1987–2007 to identify an efficient treatment to ensure maximum yield, greater sustainability, monetary returns, rainwater-use efficiency, and soil fertility over years. The results indicated that the yield was significantly influenced by fertilizer treatments in all years except 1987 1988, and 1994. The mean cotton yield ranged from 492 kg ha−1 under the control to 805 kg ha−1 under 25 kg nitrogen (N) [farmyard manure (FYM)] + 25 kg N (urea) + 25 kg phosphorus (P) ha−1. Among the nutrients, soil N buildup was observed with all treatments, whereas application of 25 kg N + 12.5 kg P ha−1 exhibited increase in P status. Interestingly, depletion of potassium (K) was recorded under all the fertilizer treatments as there was no K application in any of the treatments. An increase in soil N and P increased the plant N and P uptake respectively. Using relationships of different variables, principal component (PC) analysis technique was used for assessing the efficiency of treatments. In all the treatments, five PCs were found significant that explained the variability in the data of variables. The PC model of 25 kg N (FYM) + 25 kg N (urea) + 25 kg P ha−1 explained maximum variability of 79.6% compared to other treatments. The treatment-wise PC scores were determined and used in developing yield prediction models and measurement of sustainability yield index (SYI). The SYI ranged from 44.4% in control to 72.7% in 25 kg N (FYM) + 25 kg N (urea) + 25 kg P ha−1, which attained a mean cotton yield of 805 kg ha−1 over years. Application of 25 kg N (FYM) + 25 kg N (urea) + 25 kg P ha−1 was significantly superior in recording maximum rainwater-use efficiency (1.13 kg ha−1 mm−1) and SYI (30.5%). This treatment also gave maximum gross returns of Rs. 30272 ha−1 with benefit–cost ratio of 1.60 and maintained maximum organic carbon and available N, P, and K in soil over years. These findings are extendable to cotton grown under similar soil and agroclimatic conditions in any part of the world.

Assessment of Biomass, Productivity and Sustainability of Soybean Based Cropping Systems at Three Levels of Nitrogen in Deep Vertisols of Semi-Arid Tropical India

ABSTRACT In a 2-year field experiment (2001/02-2002/03) on deep Vertisols of Bhopal, India, the production potential, economic feasibility and nutrient balance of five cropping systems (soybean, sorghum and maize as sole crops, soybean + sorghum and soybean + maize as intercrops) each at 0%, 75% and 100% recommended dose of nitrogen (RDN) during rainy season were evaluated followed by growing wheat with RDN during post-rainy season. The results indicated that sole cropping of sorghum and maize recorded higher biomass yield than sole soybean and their intercrops. In contrast, the biomass yield of wheat during post rainy season was higher when the preceding crops were sole soybean or soybean + maize intercropping. At N0 level, intercropping of soybean + maize followed by wheat system was more productive and remunerative with a gain of 7.7 and 27.0 kg/ha of soil available P and K, respectively, but resulted in a net loss of 4.0 kg/ha of soil available N over a period of 2 years. This cropping system was less susceptible to runoff and soil erosion. At 75% and 100% recommended N levels, maize-wheat system was more productive and remunerative with a gain of 2.0 and 5.8 kg/ha of soil available N, 9.0 and 7.8 kg/ha of soil available P and 35.0 and 28.4 kg/ha of soil available K, respectively. However this cropping system resulted in higher runoff and soil loss. Adopting appropriate agronomic and soil conservation measures may correct the negative aspect of this system.

Does Particle Size of Clinoptilolite Zeolite Have a Role in Textural Properties? Insight through Differential Pore-Volume Distribution of Barret, Joyner, and Halenda Model

Analysis of differential pore-volume distribution (PVD) patterns of commercial clinoptilolite fractions [(<125 µ (Z8; fine), 125–250 µ (Z9; medium), and >250 µ (Z10; coarse)] has been conducted experimentally using an analyzer to measure the nitrogen (N2) adsorption isotherms. The differential PVDs of the clinoptilolite fractions were calculated from the hysteresis loop according to the adsorption and desorption curves of the Barret, Joyner, and Halenda (BJH) model. The adsorption and desorption cycles of BJH produced heterogeneous as well as dissimilar differential PVD patterns with assorted peaks. While the adsorption curve has prolonged up to 300 nm, the desorption cycle was confined up to 190-nm pore diameter only. In the adsorption cycle, all the clinoptilolite fractions displayed U-shaped curves and had a differential pore volume in the range of 3 × 10–3 to 8 × 10–3 cm3/g A° in the micropore region with a sole peak at 1.75 nm for the fine fraction (Z8). In contrast, the curves were linear in the mesoporous region for all the fractions, with the fine fraction (Z8) having the greatest differential pore volume, whereas the other two fractions were almost parallel to each other. The desorption cycle has revealed an inverted V-shape curve with no definite patterns for the microporous region. Although the adsorption cycle could ascertain the micropore region, the desorption cycle was unable to do so. It was apparent from the differential PVD of the BJH model that fraction size has a major role in determining the textural properties of clinoptilolite fractions.