SUSTAINABILITY OF CROP SEQUENCES WITH REFERENCE To NUTRIENT UTILIZATION

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1 Philippine Journal of Crop Science 2002, 27(2): Copyright 2004, Crop Science Society of the Philippines Released December 2004 SUSTAINABILITY OF CROP SEQUENCES WITH REFERENCE To NUTRIENT UTILIZATION SR PASCUA JR, DA VALENCIA, AT PADRE, TF MARCOS, SR OBIEN & W REICHARDT Paper presented during the 32nd Annual Scientific Conference of the Crop Science Society of the Philippines (CSSP) from April 2002 at Bohol Tropics Resort, Tagbilaran City, Bohol, Philippines A long-term field trial, from 1991 to 2000, was conducted in an isohyperthermic udic eutropept clay loam to determine the effect of inteified cropping and fertilizer application on the nutrient status of the soil and crop yield, and to find out the influence of crop residue addition on the yield of rice. There were 5 levels of N applied to rice (0, 30, 60, 90, 120 kg/ha) and 5 cropping systems such as rice-corn-mungbean, rice-mungbean-corn, rice-garlic-mungbean, rice-sweet pepper-corn and rice-tomato-corn applied with or without the recommended rates of fertilizer for each main dry season (DS) crop. N fertilizer applied at 90 kg N/ ha produced a yield of 3.88 t/ ha, and at 120 kg N/ ha a yield of 4.28 t/ ha. A change of variety from BPI Ril 0 to PSB Rcl 4 increased yield to t/ ha regardless of N rates applied. Crop residue added increased rice grain yield from 0.4 to 0.6 t/ ha specifically in fertilized DS crops. Fertilizer applied to the main DS crop had a residual effect of increasing rice grain yield from 0.4 to 0.9 t/ ha in rice-sweet pepper-corn, rice-tomato-corn and rice-garlic-mungbean systems. Except mungbean, DS crops applied with the recommended rate of fertilizer significantly produced higher yields. In fertilized plots, yield of glutinous green corn as relay to sweet pepper ranged from 0.14 to 5.31 t/ ha, and as relay to tomato from 0.54 to 4.42 t/ ha. Plots applied with the recommended rates of fertilizer regardless of DS crops showed higher soil N than the unfertilized plots in the 1997 and 1999 samplings. The rice-cornmungbean system had a higher soil N, 0.113%, than rice-mungbean-corn, 0.104%. In 1999, plots applied with the recommended rate of fertilizer showed a higher carbon content, 1.39%, than the unfertilized plots, 1.35%. The rice-garlic-mungbean system contributed significantly on the build-up of extractable K in the soil due to the rice straw used as mulch weighing about 10.7 t/ ha, with mean equivalent K value of 258 kg/ha/ year or 10 bags of KCl. For net savings each year with crop residue utilization, the rice-garlic-mungbean system had P 7, and the rice-corn-mungbean system P 5, Keywords corn, crop residue addition, cropping systems, fertilizer application, inteified cropping, mungbean, nutrient status of soil, rice, tomato INTRODUCTION Soil productivity in the lowlands of Ilocos Region is very much dependent on rainfall amount and distribution during the wet season (WS), or availability of water from tube wells, creeks and small farm reservoirs during the dry season (DS) cropping. For the last 22 years, the mean annual rainfall was 1,979 mm, with much of the rain received during heavy typhoo, about 80% of this occurring from July to October. During the rainy season, there are times when there are flash floods alternating with limited rainfall,

2 the latter causing soil drying. Intermittent flooding and drying of the rainfed lowlands can hasten the nitrification and denitrification processes, causing greater N loss and weed problems. After rice, the major DS crops grown are: garlic, onion, corn, mungbean, tobacco, tomato, sweet pepper and other vegetables. Intercropping or relay cropping with glutinous corn, mungbean or other short duration crops is usually done to increase soil productivity as well as income of the family. Such intercropping or relay cropping practices in the Ilocos could also maximize utilization of fertilizer and water input, hence increasing the fertilizer use efficiency and water use efficiency during the droughty soil condition. This study was part of the Rainfed Lowland Rice Research Coortium (RLRRC) project and was conducted to determine the effect of inteified cropping and fertilizer application on the nutrient status of the soil and on crop yield, as well as to find out the influence of crop residue addition on the yield of rice. MATERIALS & METHODS Study site The study was conducted at Mariano Marcos State University (MMSU) in Batac, Ilocos Norte, with its humid tropical climate characterized by distinct hot and dry weather from November to June and a mooon season from June to October. The experimental site is located on a flat plain of a fluvial sediment (Subagjo & Aragon 1993). The soil is moderately drained, with a groundwater table at a depth of 9-10 m during the dry months. Experimental design & treatment Treatments were laid out in strip splitplot design with 4 replicatio, and the plot size was 45 m2. The rates of N fertilizer applied during the WS ( ) to rice were 0, 30, 60, 90 or 120 kg N/ha, plus a blanket application of 13 kg P/ha (increasing to 26 kg P/ha in the 1995 WS) and 25 kg K/ha. The cropping systems (WS-DS-relay crop) were rice-tomato-corn, rice-sweet pepper-corn, rice-mungbean-corn, rice-garlicmungbean and rice-corn-mungbean. DS crops were either unfertilized or given recommended rates of N, P and K per ha in elemental form. The rates for the DS crops were for garlic, for sweet pepper and tomato, for mungbean and for corn. For rice, the whole amounts of single superphosphate and muriate of potash were applied as a basal application. N was applied to rice in 4 equal split applicatio: as basal, at mid-tillering, at panicle initiation and at flowering. The rice variety was changed from BPI RHO to PSB Rc14 during the 2000 WS since PSB Rc14 is the commonly used variety in the Ilocos. The whole amount of NPK was applied as a basal in mungbean. For sweet pepper and tomato, a basal application of kg NPK/ha was done, kg applied 2 weeks after traplanting and kg 1 month after traplanting. For corn, all of the P and K were applied as basal, and one-third of the N was applied each as basal, at 30 days after planting (DAP) or before hilling-up, and at 60 DAP. For garlic, all the P and K and two-thirds of the N were applied during sowing, and rice straw at 10.7 t/ha was applied as a mulch immediately after sowing. The last third of the N was applied at 60 DAP or during early bulb formation. From 30 to 60% of the mulch used for garlic was taken from outside sources. All the relay crops were not fertilized except during the 2000 DS cropping wherein corn relayed to mungbean was supplied with kg N-P205-K20/ha. Crop residue management All crop residues from the 1992 WS and the 1993 DS crops, including the rice straw mulch added to garlic, were incorporated into the soil at the time of land preparation for the rice crop in the 1993 WS. The annual rate of incorporated crop residues averaged 7.3 t/ha. To further confirm the effect of crop residue incorporation on the yield of rice, another treatment, with and without crop residue incorporation, was superimposed with the sweet pepper plot, starting in 1997 and continuing to the present. Soil & plant sampling & analyses The rice grain yields were measured from 5 m2, and the harvest area for the main DS and relay crops ranged from 10 to 20 m2

3 depending on the row spacing of the crop. Five plant samples from each replicate plot of the main as well as relay crops, and sample rice plants from 5 hills were chopped, ovendried and sub-sampled for NPK analysis. Soil samples were taken in 3 borings per treatment plot for NPK and C analyses. RESULTS & DISCUSSION N levels & cultivar Table 1 shows an average yield (except for 1991) of 2.18 t/ha without N fertilizer, much lower than 3.88 t/ha with 90 kg N/ha and 4.28 t/ha with 120 kg N/ha. There was a yield advantage of 0.4 t/ha with 120 kg N/ha over 90 kg N/ha, and this was still profitable. There was a corresponding increase in yield with increasing N applied. Furthermore, there was a dramatic increase in yield when the initial variety BPI Ril0 was replaced with PSB Rc14 in 2000 WS, an average increase ranging from 1.7 to 2.1 t/ha. The yields were the same between an unfertilized PSB Rc14 and BP RHO with 60 kg N/ha, and between PSB Rc14 with 30 kg N/ ha and BPI Ril0 with 120 kg N/ha. Crop residue incorporation Traplanting was done immediately after a thorough crop residue incorporation during soil puddling. Ismunadji (1978) had reported that plowing in straw at 10 t/ha 1 week before planting yielded as much as did plowing it in 2 and 4 weeks before planting, both with and without 120 kg N/ha. The effect of crop residue incorporated on rice yield ranging from 0.4 to 0.6 t/ha was observed only in plots with the recommended fertilizer rate for the DS crops. This could be due to higher biomass incorporated both from the main DS and relay crops as well as weeds, hence more nutrients available for the succeeding rice crop. This confirmed the findings of Ponnamperuma (1984), where the increase in paddy yield due to straw application, averaged for 9 years, was 0.4 t/ha per year, lower than 0.6 t/ha per year with compost application and zero for burning. Crop residue incorporated can increase rice yield by 0.49 t/ha regardless of the fertilizer applied during the DS cropping. This implies the necessity of incorporating crop residues to increase soil productivity specifically under rice-sweet pepper-corn system and other cropping systems in the Ilocos. It further implies the need for only one plowing before soil puddling to promote the growth of weeds for higher biomass to be incorporated and as weed control measure. Cropping system Table 2 shows that regardless of the N rates applied to rice, DS crops applied with Table 1. Rice grain yields as affected by N levels 1991 to 2000, MMSU, Batac, Ilocos Norte, Philippines N applied to rice (kg/ ha) Rice Grain Yield (t/ha) Mean' SED yield not included 2SED for 2 Fertilizer averages over 5 cropping sequences

4 the recommended fertilizer rate produced a higher rice yield, 5.16 t/ha, than the unfertilized crops, 4.79 t/ha. Such result could be attributed directly to the residual fertilizer and indirectly to the production of higher biomass when the relay crops served as 'catch crops' for fertilizers applied to the main DS crops and with crop residue incorporation, there was additional source of nutrients for the rice plant. Cropping systems such as rice-tomatocorn, rice-sweet pepper-corn and rice-garlicmungbean, had significant interactio with the fertilizer for DS crops on rice yield. A higher rice yield was produced with the recommended rate of fertilizer applied than with unfertilized crops. Rice-tomato-corn had a higher rice yield at 5.56 t/ha than ricesupplemented to keep the cracked soil moist. Another mild 'El Nitio' occurrence was observed in August 1998 during the panicle initiation of the rice plant, and this caused a decrease in yield. The yield of DS crops was not affected by rainfall since the experimental area had good drainage. Fertilizer application All main DS crops, except for mungbean, responded to the application of recommended amounts of fertilizer (Table 3). This could be due to the fact that mungbean is a leguminous crop, which produces N in its root nodules. However, mungbean yield was quite low in 2000, which could be attributed to the occurrence of powdery mildew when mungbean was planted in December. The Table 2. Rice yield (t/ha) as affected by the interaction between cropping system and fertilizer application to DS crops, WS 2000 Cropping System Rice Yield (t/ha) Recommended Rate Control Difference Rice-Tomato-Corn 5.56 a 4.69 ab 0.87 Rice-Sweet Pepper-Corn 4.90 b 4.50 b 0.40 Rice-Mungbean-Corn 5.15 ab 4.97 a 0.18 Rice-Corn-Mungbean 5.15 ab 5.12 a 0.03 Rice-Garlic-Mungbean 5.05 b 4.68 ab 0.37 * Mean 5.16 a 4.79 b = significant at 1% level, * = significant at 5% level. In a column and a row, mea followed by a common letter are not significantly different at the 5% level by DMRT. sweet pepper-corn at 4.9 t/ha with the same amount of fertilizer. The difference could be due to variation in nutrient uptake efficiency between sweet pepper and tomato. Rainfall The low yield in 1991 was attributed to the typhoon in October before harvest and so in 1992 and 1993 during the reproductive stage of the crop. Although the 'El Nitio' phenomenon occurred in 1995 and 1997, the yields were still high since limited rainfall occurred in July after traplanting and September. Irrigation water was then partly highest respoes to the recommended fertilizer rate were obtained in sweet pepper, tomato and corn. Results show differences in yield of mungbean between the years and this could be attributed to disease infestation and change of variety due to its unavailability during planting. Yield of relay crop The yield of relay crop was significantly affected by the recommended rate of fertilizer applied for each DS crops (Table 4). When the recommended rates of NPK were applied to

5 sweet pepper and tomato, green glutinous corn was harvested ranging from 0.14 to 5.31 t/ha and 0.54 to 4.42 t/ha, respectively. In previous years ( ), the yield of corn relayed to mungbean was very low due to the small amount of fertilizer applied to mungbean ( kg NPK/ha). However, there was a dramatic increased in green corn yield in the year 2000 both the fertilized and unfertilized treatment. Only in 2000 the corn relayed to fertilized mungbean was applied with kg N-P205-K20/ha. Mungbean planted after corn had higher yield than days during planting and irrigation due to simultaneous activities would explain differences in yield from 1994 to Soil nutrient status There seems to be an increasing trend of soil N as measured using the CHN analyzer for all the DS crops. Plots with fertilizer showed a higher soil N than the unfertilized plots during the 1997 and 1999 samplings. There was also a significant interaction between cropping system and fertilizer for DS crops. Fertilized crops had a higher soil N Table 3. Yield of DS crops as affected by fertilizer application , MMSU DS Crop/ Treatment DS Crop Yield (t/ha) Corn Control Recommended Garlic Control Recommended Mungbean Control Recommended Sweet pepper Control Recommended Tomato Control Recommended F-test: Rice-Corn * * * * * Rice-Garlic Rice-Mungbean Rice-Sweet Pepper Rice-Tomato = "It o,.,,,;fi, -,,,- t * = c/rm,f,nr-/ig coz, = clrm, n 1-10, lo,o1 relayed to garlic and this could be explained by the higher plant population. The differences in yields of relay crops could be attributed to management activities, iect damage and rainfall. A delay of 1-3 than unfertilized crops. Rice-corn-mungbean had a higher soil N, 0.113%, than ricemungbean-corn, 0.104%. It implies that not all applied N had been lost within one year cropping (rice-ds crops-relay crops).

6 Soil carbon was not affected by cropping system and fertilizer for DS crops during 1993 and However in 1999, plots and fixation; production of organic acids; and release of CO2, CH4, C2H4 and H25 (Yoshida 1978). Although all the products, except CH4, Table 4. Yield of relay crops, dry season of , MMSU RELAY CROP/FERTILIZER Relay Crop Yield (t/ha) Corn-Mungbean Control Recommended Garlic-Mungbean Control Recommended Mungbean-Corn Control Recommended Sweet pepper-corn Control Recommended Tomato-Corn Control Recommended F test R-Corn-Mungbean R-Garlic-Mungbean R- Mungbean-Corn R-Sweet pepper-corn R- Tomato-Corn = not significant. * = significant at 5% level applied with the recommended rate of fertilizer showed higher carbon content, 1.39%, than the unfertilized plot, 1.35%. Ponnamperuma (1984) had reported that 5 t straw contained about 2 t C, which in wetlands can be an indirect source of N. Because about 40% by weight of dry straw coists of biodegradable C, straw is a substrate for the growth of soil microorganisms. Thus straw incorporation in a flooded soil leads to a burst of biochemical activity: soil reduction and associated electrochemical changes; N immobilization when in excess are toxic to rice, their toxicity in fields amended with straw has not been demotrated. Furthermore, cropping system had an effect on the NPK value in the soil. Ricegarlic-mungbean contributed significantly to the build-up of extractable K due to the rice straw used as mulch weighing about 10.7 t/ha, with mean equivalent K value of 258 kg/ha/year (Table 5). Furthermore, extractable K value increased through the years in all the cropping systems whether fertilized or not. It implies then that we can

7 maintain extractable K in soil and even increase it if there is continuing crop residue incorporation. Rice-garlic-mungbean had a diversified cropping can only produce an average rice grain yield of 2.0 t/ha without any N applied (but applied Table 5. Nutrient contribution (kg/ha) of crop residues incorporated under the different cropping systems applied with the recommended rate of fertilizer for DS crops from 1993 WS-1995 DS, MMSU, Batac, IN. Cropping Systems/ NPK Applied Rice-corn-mungbean 0-0-0/ / Mean Rice-mungbean-corn N P Kg/ha K / / Mean Rice-garlic-mungbean 0-0-0/ / Mean Rice-tomato-corn 0-0-0/ / Mean Rice-sweet pepper-corn 0-0-0/ / Mean net saving of P 7,425 and rice-corn- with 60 and 30 kg P2O5 and K2O, mungbean P 5,739 per year with crop residue respectively) on rice. An application of utilization (Table 6). 120 kg N/ha increased yield by 0.4 t/ha and a net income of P (P CONCLUSION & RECOMMENDATION 8.50/kg of palay) over the 90 kg N/ha application. There is a yield difference Based on the results of this study the of 2.1 t/ha and a net income of P 13, following conclusio and recommendatio when applied with 120 kg could be derived: N/ha over that of rice without N 1. Inteively cultivated soil with fertilizer applied.

8 2. For higher soil productivity, crop residue incorporation should be practiced, which mea a rice grain yield increase from 0.4 to 0.6 t/ha, equivalent to P to P per cropping. 3. The residual fertilizer from diversified cropping systems, ie, rice-sweet pepper-corn, rice-tomato-corn and rice-garlic-mungbean, can increase an average rice grain yield from 0.4, 0.9 and after bulb formation for garlic. It is still possible to plant mungbean after corn specially when there is an early planting of corn to possibly harvest mungbean before the oet of strong rai in May. 6. There is an increasing trend of soil N and quite stable in all the cropping systems with or without fertilizer applied for the main DS crops. Not all applied N is lost within one year Table 6. Nutrient contribution of crop residues in terms of fertilizer (bags) and amount saved from different cropping systems 1993 WS-1995 DS, MMSU, Batac, Ilocos Norte.* Cropping Systems Fertilizer Material, bags/ha/ Value (P) Value Value Value Rice-Corn , ,004 Mungbean Rice-Garlic , ,304 Mungbean Rice-Mungbean ,236 Corn Rice-Tomato-Corn , ,974 Rice-Sweet pepper , ,881 Corn and 0.37 t/ha and increased income of p , p and P respectively, per cropping. 4. There is no need to apply kg N-P205-K20 kg/ha on mungbean. Rice straw continuously incorporated in a rice-garlic-mungbean system can improve the yield of unfertilized garlic which is comparable to garlic applied with kg NPK/ha for some years. 5. It would be better to relay corn to sweet pepper and tomato (with highfertilizer input) to make use of the residual fertilizer and mungbean or cowpea to garlic (with low-fertilizer input). The crops relayed are not applied with any fertilizer. Relay cropping should be done before the main crop canopy close-in such as sweet pepper, tomato and mungbean cropping (rice-ds crops-relay crops). 7. The highest P values in the soil are observed from rice-tomato-corn and rice-garlic-mungbean systems. When DS crops are not applied with the recommended rate of fertilizer, available P in soil is utable and possibly depleted in the long run with an inteified cropping system. 8. The highest K values are observed from rice-tomato and rice-garlic systems. Rice-garlic has a significant build-up of soil K due to the incorporated rice straw as mulch weighing about 10.7 t/ha with a mean equivalent K value of 258 kg/ha yr-1, or a saving of p It implies that there is no need to apply K fertilizer during the rice cropping. 9. Soil K is increasing through the years in all the cropping systems whether

9 with or without fertilizer. This mea that crop residue incorporation is an important practice. 10. Rice-garlic-mungbean and rice-cornmungbean have a net savings of P and P per year, respectively, with crop residue utilization. LITERATURE CITED Ismunadji M Utilization of cereal crop residues and its agricultural significance in Indonesia. Countryside Center Research Ititute for Agriculture, Bogor pp Ponnamperuma FN Straw as a source of nutrients for wetland rice. In Organic Matter and Rice. IRRI. pp Subagjo H and EL Aragon Characterization and Classification of Soils in: Rainfed Lowland Coortium Sites. Second RLRRC Technical Meeting February Semarang, Indonesia Yoshida T Microbial metabolism in rice soils. In Soils and Rice. IRRI pp