Section 3 (Crop Management)

More documents

Recommendations

Info

Proceedings of the 8 th Asian Regional Maize Workshop, Bangkok, Thailand: August 5-8, 2002 Effect of Phosphorus Availability on Growth, P Uptake, and Efficiency in Maize Soybean Intercrops in Different Environments Neeranjan P. Rajbhandari* CIMMYT, Nepal. E-mail: npr@mos.com.np Abstract While there is an abundance of experimental results on increased productivity of intercrop systems, the interpretations are limited to the effect of increased crop diversity on reducing insect and disease attack, and increasing the efficiency of resource utilization. There is a dearth of information on how intercrops respond to varying levels of P availability leading to greater efficiency. The present experiment was conducted at the University of Hawaii to evaluate a maize/soybean intercrop system for periodic dry matter production, leaf P concentration and leaf properties. P uptake and its conversion efficiency were evaluated to determine whether the increased productivity of the mixture was only due to increased uptake of resources or efficient conversion to dry matter or grain yield by intercrop components under competition. Growth of intercrop maize was no different than the sole crop for their periodic dry matter, P concentration, and P uptake, but was profoundly affected by environment and P availability in the soil. The response of intercrop soybean to environment and P level was more complex and differed from that of the sole crop. Interactions between environment, P level, and the growth conditions of the companion maize determined the response of intercrop soybean. Soybean leaf tissue P concentration and P uptake was influenced by environment, P levels, and system (intercrop versus sole crop) and their interactions. The increased productivity of the intercrop combination was associated with increased extraction of soil phosphorus. In low-input subsistence agriculture, the accelerated P mining -- the faster removal of limited soil P -- may cause the intercrop systems to be less sustainable. There is no alternative to P fertilization in such systems for long-term sustainability. Introduction The differential ability of plant species, and even cultivars of the same species, to extract and utilize soil phosphorus is well documented. Plant species grown in solution culture required different P concentration for optimum growth (Asher and Loneragan 1967). Some species required 0.03 mg/L, while others required 25 times more (Fox 1981). When two crops are grown together as an intercrop, availability of P is affected by the overlapping of depletion zones around the roots of the same as well as different species. The competition for P by two species should also be dependent upon the combined demand for P and the amount of P in the soil solution which is the major factor controlling the flux of P to plant roots. Whether intercropping, with the greater demand or the expected faster depletion of the soil solution P, will result in a different uptake and efficiency of phosphorus at different P availability has not been investigated. Very little is known about P competition in intercrops especially maize/soybean intercrops. It is generally expected that P concentration in leaves of the sole crop and intercrop are the same at the beginning of the growth cycle and any difference in concentration at later stages can be attributed to interference. Also, the total P uptake and dry matter accumulation by an intercrop combination can be expected to be greater than that of the sole crop throughout the growth stages. Results of Chang and Shibles (1985) are conclusive in this regard for a maize/cowpea intercrop in a replacement series experiment. - 214 -
Rajbhandari Extensively cited data of Dalal (1974) indicated that total P uptake (6 and 16 weeks after planting) by sole crop maize was greater than a maize/pigeonpea intercrop. The intercrop pigeonpea P uptake was less than that of the sole crop at 6 and 16 weeks after planting, but at 24 weeks there was no difference between sole and intercrop P uptake. The soil P status remained unaffected 16 weeks after planting. Srinivasan and Ahlawat (1983) also recorded no difference in soil P status between sole crop pigeonpea and intercrop with green gram or sorghum. Wahua (1983) observed no difference between P uptake (up to 50 DAP) of sole and intercrop maize; however, at higher fertility levels uptake by the sole crop was greater than intercrop and the reverse was true at lower fertility levels. The uptake by intercrop cowpea was much lower than the sole crop 40 days after planting. CIAT (1980) reported lower P concentration in leaves of intercropped cassava and cowpea compared to sole crops. Mason et al (1986) observed that intercropping cassava with cowpea reduced the P concentration in leaf, stem and storage roots of cassava at early growth stages (till 80 days after planting) but not after. Most of the experiments reviewed were conducted with adequate P fertilization, and none of them dealt with intercrop response to P across a range of P levels in different environments. Intercrop systems have been advocated to be more efficient in land use compared to sole crop systems, and therefore suitable and desirable in sustainable agriculture. It is unclear whether the increased efficiency is due to only more resource extraction or to more efficient conversion of resources to dry matter and marketable yield. The experiment under different environments were conducted with the following objectives: • To compare the growth in dry matter and grain yield maize and soybean in maize/soybean and maize/rice intercrops with sole crops under different environments. • To quantify the effect of interspecific competition on P uptake and conversion efficiency of intercrops compared to sole crops under different P availability. Materials and Methods Two sites in Hawaii, having contrasting soil and climatic conditions, were utilized to conduct an experiment in three environments. Permanent plots were utilized for the intercropping experiments, where ten target phosphorus concentration in soil solution have been established since 1971. The field trial at Wailua Experiment Station, Kauai, was planted on a highly weathered clayey, sesquic, isothermic, Anionic Acrudox. Two field trials were conducted during the summers of 1988 and 1989 at the University of Hawaii Poamoho Experiment Station on a silty clay of the Wahiawa series classified as clayey, kaolinitic, isohyperthermic, Rhodic Eutrustox. Main plots of ten target P levels (0.003, 0.006, 0.012, 0.025, 0.05, 0.1, 0.2, 0.4, 0.8, 1.6 mg P/L in soil solution) were laid out in an augmented block design (Federer 1956). The target P levels in soil solution were achieved using phosphorus sorption techniques (Fox and Kamprath 1970). Appropriate amounts of P fertilizer in each treatment were applied as triple superphosphate before the last tillage operation to achieve the targeted levels of P in soil solution. In Kauai the four middle P levels (0.025, 0.05, 0.1 and 0.2 mg P/L) were replicated three times, the four extreme levels (0.003, 0.006, 0.8 and 1.6 mg P/L) occurred only once and the remaining two (0.012 and 0.4 mg P/L) were replicated twice. Each of 20 main plots (12.19 m by 9.14 m) contained each of the three sole crops (maize, rice and soybean) along with maize/rice and maize/soybean intercrops. In Poamoho, four P levels, 0.012, 0.025, 0.050 and 0.100 mg P/L, were replicated three times and the rest of the unreplicated treatments constituted the 18 main plots (15.24 m by 5.49 m). Each main plot in 1988 contained one of the sole crops (maize, rice or soybean) and the two intercrop patterns. In 1989, main plots contained the maize/soybean intercrop with both maize and soybean sole crops. Maize spacing was 0.90 m by 0.25 m for both sole crop and intercrop. Sole crop - 215 -
Page 1 and 2: Section 3: Crop Management - 203 -
Page 3 and 4: Proceedings of the 8 th Asian Regio
Page 5 and 6: Maize in the rice-wheat rotation gr
Page 7 and 8: Maize in the rice-wheat rotation Av
Page 9 and 10: Maize in the rice-wheat rotation RW
Page 11: Maize in the rice-wheat rotation Ta
Page 15 and 16: Rajbhandari There was a linear resp
Page 17 and 18: Rajbhandari sole crop soybean was m
Page 19 and 20: Table 3. Sample means for phosphoru
Page 21 and 22: Rajbhandari Table 5. P use efficien
Page 23 and 24: Appendix 1 a. Combined analysis of
Page 25 and 26: Rajbhandari Appendix 2a. Combined a
Page 27 and 28: Rajbhandari Appendix 2b. Combined a
Page 29 and 30: Proceedings of 8 th Asian Regional
Page 31 and 32: Soil fertility in the hills of Nepa
Page 33 and 34: Soil fertility in the hills of Nepa
Page 35 and 36: Experimental Findings (Based on sta
Page 37 and 38: Quayyum treatment T2 i.e., maize no
Page 39 and 40: Table 1. Yield and yield components
Page 41 and 42: Table 5. Effect of different fertil
Page 43 and 44: Table 8. Cost & return analyses of
Page 45 and 46: Table 13. Cost-benefit analysis of
Page 47 and 48: Proceedings of 8 th Asian Regional
Page 49 and 50: Maize-wheat systems measured under
Page 51 and 52: Literature Cited Maize-wheat system
Page 53 and 54: Table 2. Growth and yield attributi
Page 55 and 56: Maize-wheat systems Table 4. Balanc
Page 57 and 58: grain yield and eff. tillers grain
Page 59 and 60: Proceedings of the 8 th Asian Regio
Page 61 and 62: Results and Discussion Maize in eas
Page 63 and 64:
Maize in eastern hills of Nepal Tab
Page 65 and 66:
Yield kg/ha 7000 6000 5000 4000 300
Page 67 and 68:
Maize in eastern hills of Nepal App
Page 69 and 70:
Pokharel et al. backgrounds, we hav
Page 71 and 72:
Proceedings of the 8 th Asian Regio
Page 73 and 74:
Results and Discussion N-requiremen
Page 75 and 76:
Rainfall (mm) 800 700 600 500 400 3
Page 77 and 78:
N-requirement in maize/millet relay
Page 79 and 80:
Appendix I. Weather Information rec
Page 81 and 82:
Tripathi It is necessary to manage
Page 83 and 84:
Results and Discussion Tripathi Mai
Page 85 and 86:
Literature Cited Tripathi App (Nepa
Page 87 and 88:
Table 4. Treatment combinations and
Page 89 and 90:
Table 6. Grain yield of maize (t/ha
Page 91 and 92:
Maize grain (t/ha) 8 7 6 5 4 3 2 1
Page 93 and 94:
Maize grain (t/ha) 10 9 8 7 6 5 4 3
Page 95 and 96:
Labios et al. surface is left undis
Page 97 and 98:
Labios et al. Figures 3 and 4 showe
Page 99 and 100:
Labios et al. Labios R.V.; Robles,
Page 101 and 102:
Figure 1. Farmers planting corn usi
Page 103 and 104:
Figure 5a. Status of the field at p
Page 105 and 106:
Proceedings of the 8 th Asian Regio
Page 107 and 108:
Maize-rice rotation in Thailand On-
Page 109 and 110:
Maize-rice rotation in Thailand Fro
Page 111 and 112:
Maize-rice rotation in Thailand Tab
Page 113 and 114:
Maize-rice rotation in Thailand Tab
Page 115 and 116:
Harris et al. humid, sub-tropical c
Page 117 and 118:
Harris et al. In Pakistan, priming
Page 119 and 120:
Table 2. Effect of priming duration
show all

Section 3 (Crop Management)

Create successful ePaper yourself

Delete template?

Save as template?