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Production Papers

Influence of Residual Nitrogen and Tillage on White Lupin

^a Dep. of Agronomy, Univ. of Florida, 155 Research Rd., Quincy, FL 32351
^b Dep. of Plant Pathology, North Florida Res. and Educ. Center, Univ. of Florida, 155 Research Rd., Quincy, FL 32351

^* Corresponding author (pjwiatrak{at}mail.ifas.ufl.edu)

Received for publication April 16, 2004.

	ABSTRACT

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
White lupin (Lupinus albus L.) yield and forage quality depend on the tillage and residual N from a previous crop. The objective of this study was to evaluate the response of winter white lupin seeded in two tillage systems [strip-till (ST) and conventional (CT)] to four N rates applied to a previous cotton (Gossypium hirsutum L.) crop (0, 67, 134, and 202 kg ha^–1). The experiment was conducted in 1995–1996 and 1996–1997 growing seasons. The influence of residual N from a previous cotton crop on white lupin dry matter and grain yields, and silage N concentration varied from year to year. Residual N did not influence silage in vitro organic matter digestion (IVOMD), neutral detergent fiber on a dry matter (DM) basis (NDFt), or neutral detergent fiber ash-free (NDFaf). However, the weight of 1000 lupin seeds increased by 0.07 g for every 1 kg N applied to a previous cotton crop. Dry matter and grain lupin yields were 15 and 31% greater from ST than CT, respectively. Silage NDFt and NDFaf from ST were 6% greater than that from the CT system. However, the IVOMD, N, and P concentrations were 2, 11, and 27% greater from CT than ST, respectively. The results of this study indicate that greater dry matter and grain yields, NDFt, and NDFaf, and lesser IVOMD, N, and P concentration may be obtained from ST than CT. However, the influence of residual N on dry matter and grain yields of white lupin needs to be further defined.

Abbreviations: CT, conventional tillage • IVOMD, in vitro organic matter digestion • NDFaf, neutral detergent fiber ash-free • NDFt, neutral detergent fiber on a dry matter (DM) basis • ST, strip-till

	INTRODUCTION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
LEGUMES ARE USED commonly in agricultural systems as a source of N for subsequent crops and for maintaining soil N levels (Glasener et al., 2002) and reducing energy requirements by adding significant amounts of N to the soil (Entz et al., 2002). Grant et al. (2002) noted that cropping systems that include legumes have the potential for contributing N to following crops and may moderate NO₃ levels in the soil to avoid potential for NO₃ leaching. Interest in white lupin in the southeastern USA (Reeves et al., 1991) has increased during the past 20 yr (Noffsinger et al., 2000). Winter-type white lupin can be used directly on the farm in late spring when other sources of high-protein livestock feed are not available (Noffsinger et al., 2000). According to Reeves et al. (1999), winter-type white lupin could also be used in rotation with summer annual crops to improve the long-term sustainability of cropping systems in the Southeast. In 1940s, white lupin was grown as green manure for cotton (Reeves et al., 1990), which is an important summer crop in the southeastern row production systems (Buntin et al., 2002).

Crops grown in previous years impact the amounts of residual nutrients available for subsequent plant growth (Gan et al., 2003). Grant et al. (2002) noted that crops differ substantially in the amount of N returned in the crop residue for use by subsequent crops primarily due to the quantity of crop residue and N concentration of residue. High levels of crop residue can adversely affect yields, thereby slowing adoption of conservation tillage practices that effectively control soil erosion (Rasmussen et al., 1997). The management of N plays a key role in improving crop quality (Campbell et al., 1995) and optimal N management will be influenced by crop type and rotation (Grant et al., 2002). The level of N in the soil may increase due to N returned to the system from the previous crop (Grant et al., 2002), N not taken up by the previous crop (either fertilizer or mineralized), and mineralized N from soil organic matter. This increased N must be taken into consideration, because it may pose a risk to the environment (Woolfolk et al., 2002). Grant et al. (2002) noted that synchrony of nutrient supply with crop demand is essential to ensure optimum crop yield and quality, while avoiding negative environmental impacts. Research showed a positive influence of soil residual N on legumes. For example, increasing N fertilizer rates to the preceding wheat crop increased seed yield, total dry matter, and N uptake of faba bean (Vicia faba L.) (López-Bellido et al., 2003). López-Bellido et al. (2000) found that the optimum N rate of 100 kg ha^–1 applied to a wheat crop has a positive effect on the following faba bean crop.

Diversified crop rotations can increase yield potential by influencing plant diseases, weeds, root distribution, moisture utilization, and nutrient availability (Campbell et al., 1990), and sustainable cropping systems are essential for agronomic, economic, and environmental reasons (Camara et al., 2003). Intensification and diversification of cropping systems influence nutrient demand, cycling, and distribution within the soil profile (Grant et al., 2002) and increase yield potential by influencing nutrient availability (Campbell et al., 1990). Carranca et al. (1999) observed that incorporating harvest residues from a previous crop results in a significant net increase in soil N compared with removing residues. However, yields may also decrease with intensification and diversification of crop rotations due to nutrient availability. Therefore, appropriate tillage and fertilizer management practices need to be developed for sustainable crop production without jeopardizing the soil quality and environment (Ishaq et al., 2001).

Strip tillage is the most common conservation tillage system in the southeastern USA, and the system uses a seed-bed preparation implement with in-row subsoil shanks, multiple coulters, and ground driven crumblers that till a band approximately 30 cm wide (Johnson et al., 2001). They noted that crops can be planted with planter units mounted on the tillage implement or as a separate operation. Reduced tillage methods present many advantages in terms of timeliness, lower economic cost and energy consumption, and appear to be a good alternative practice compared with CT (Gemtos et al., 1998). Also, water conserved through use of reduced tillage compared with the more intensive conventional tillage my help a grower to take advantage of the often low and erratic growing-season precipitation (Grant et al., 2002). Allen and Entz (1994) noted that reduced tillage forage establishment decreases risk of soil erosion, increases soil water available to germinating forage seeds, and increases plant establishment compared with conventional tillage. Based on research with faba bean, yields may be similar (Izaurralde et al., 1993) or greater under conservation than conventional tillage (Abdel-Daiem et al., 1988). In contrast, Izaurralde et al. (1995) reported greater faba bean yields under deep tillage than conservation tillage. Farmers have been slow of adopting conservation tillage, due to usually lower crop yields (Cosper, 1983). Little research has been conducted concerning the effects of tillage and residual N and on white lupin. Therefore, the objective of this study was to evaluate the impact of residual N on white lupin grown in ST and CT systems.

	MATERIALS AND METHODS

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
Field trials with white lupin were conducted in 1995–1996 and 1996–1997 on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) at the University of Florida North Florida Research and Education Center in Quincy, FL. Treatments consisted of two tillage systems for white lupin [strip-till (ST) and conventional tillage (CT)] and four N rates band applied in the form of ammonium nitrate (34–0–0, N–P–K) to the previous cotton crop (0, 67, 134, and 202 kg N ha^–1). After picking cotton, the study was mowed and plant residues were left in the field. The ST and CT in white lupin followed ST and CT in previous cotton crop, respectively. White lupin ST sections of the study were broadcast sprayed with glyphosate [N-(phosphonomethyl) glycine] at 576 g a.i. ha^–1 2 wk before sowing white lupin. One d before implementing tillage treatments, all plots were fertilized with 28, 24, and 70 kg ha^–1 of N–P–K, respectively. A Brown Ro-till implement (Brown Manufacturing Co., Ozark, AL) was used to till a band approximately 18 cm wide with 91 cm between row centers and 25 cm deep 1 d before sowing lupin. At the same time, conventional sections were subsoiled approximately 25 cm deep, disc-harrowed 15 cm deep, and leveled with the s-tine harrow. Before sowing, white lupin seeds were inoculated with Bradyrhizobium sp. lupini inoculum (LiphaTech, Milwaukee, WI). The ST and CT sections were seeded with white lupin cv. ‘Lunoble’ at 174 kg ha^–1 and 2.5 cm deep in double 21.6 cm wide row spacing with 91 cm between double row centers, using a modified KMC planter (Kelley Manufacturing Co., Tifton, GA) on 23 Nov. 1995 and 1996. The subplots were 6.1 m long and 3.7 m wide. A field cultivator was used between lupin rows in CT sections on 8 Feb. 1996. All plots were broadcast sprayed with tebuconazole (-[2-(4-chlorophenyl)ethyl]--(1,1dimethylethyl)-1H-1,2,4-triazole-1-ethanol) at 227 g a.i. ha^–1 on 4 Apr. 1996, and 3 Mar. and 4 Apr. 1997. Lupin samples for silage were cut 2 to 3 cm above the ground using a sickle bar mower (Garden Way, Troy, NY) on 22 Apr. 1996 and 1997. After cutting, all lupin samples were weighed and subsamples (908 g each) were placed in a forced-air drier at 60°C for a maximum of 10 d. During this process these subsamples were checked frequently. There was no or very little effect on the silage quality analysis as a result of holding these samples in the drier for an extended period due to the weight of each subsample. After drying, all subsamples were weighed and ground to pass through a 1-mm screen.

The IVOMD, NDFt, NDFaf, N, and P were determined from the whole plant samples cut for silage. The in vitro organic matter digestion (IVOMD) was performed by a modification of the two-stage technique (Moore and Mott, 1974). The neutral detergent fiber on a DM basis (NDFt) and ash-free (NDFaf) were determined using the procedure of Golding et al. (1985). For P and N analysis, samples were digested using a modification of the aluminum block digestion procedure of Gallaher et al. (1975). Sample weight was 0.25 g, catalyst used was 1.5 g of 9:1 K₂SO₄–CuSO₄, and digestion was conducted for at least 4 h at 375°C using 6 mL of H₂SO₄ and 2 mL H₂O₂. Phosphorus and N in the digestate was determined by semiautomated colorimetry (Hambleton, 1977).

Plant heights were obtained from 20 randomly selected plants 2 wk before white lupin harvest for grain. Heights were determined by measuring from the ground to the top of plants. Lupin was harvested for grain with a small plot combine on 11 June 1996 and 9 June 1997. At harvest, seeds from each plot sample were weighed and analyzed for moisture, yields were adjusted to 100 g kg^–1 moisture, and the weight of 1000 seeds was recorded.

The Southeast region of the USA (25–37°N lat, 75–97°W long), dominated by a temperate–humid climate, has an average temperature of 18.3°C and yearly precipitation of 2041 mm (Buol, 1973). Most of the warm-season annual crops grown in this region need 125 to 160 d of vegetation and may be double cropped. Soils in the southeastern USA (mineral soils with low level of organic matter) are acidic and highly weathered due to the age of the parent material and climate (Buol, 1973).

Weather data was collected near the test sites from a weather station located at the North Florida Research and Education Center, Quincy, FL (30°36'N lat, 84°33'W long). The monthly air temperatures and rainfall with 20-yr average and sum, respectively, during the two growing seasons are shown in Table 1. The temperatures and rainfall varied from year to year. Compared with the 20-yr average, air temperatures were 0.7 and 1.4°C higher in October and May, respectively, in the 1995–1996 growing season. During the same year, temperatures were 2.6, 1.4, 2.4, and 1.6°C lower in November, December, March, and April, respectively, than the average. In the 1996–1997 growing season, monthly air temperatures were 3.9, 2.6, and 1.2°C higher in January, March, and May, respectively; and 1.1 and 1.6°C lower in November and April, respectively. Compared with the 20-yr monthly total, the rainfall was 84 and 90 mm higher in October and April, respectively, and 80, 86, and 92 mm lower in January, May, and June, respectively, during the 1995–1996 season. In 1996–1997, however, monthly rainfall was 59 and 80 mm higher in October and April, respectively, and 59 and 60 mm lower in November and March, respectively.

The field experimental design was a split plot arranged in a randomized complete block with four replications. Tillage was the main plot and N application to a previous cotton crop was the subplot. All data was analyzed using a PROC MIXED model (SAS Inst., 1999). These experiments were conducted on the same site. As years were sequential with potentially cumulative effects on soil and plant parameters, years were considered fixed effects. Tillage systems and N applications to a previous cotton crop were considered fixed. Blocks and interactions including blocks were assumed to be random effects. The PROC MIXED procedure of SAS with the LSMEANS PDIFF option was used to test effects of tillage systems, N applications to a previous cotton crop, and their interactions on white lupin. The difference between means for tillage and N applications to a previous cotton crop were considered significant at P 0.05. Single degree-of-freedom contrasts were used to evaluate linear and quadratic effects of N applications on cotton. When a contrast indicated that there was a significant (P 0.05) linear or quadratic response, then a linear or quadratic regression model, respectively, was fit using PROC REG (SAS Inst., 1999).

	RESULTS AND DISCUSSION

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
Residual soil N generally increased with increasing N application to the previous cotton crop under ST and CT in 1995 and 1996 (Table 2). Compared with the treatment without N application, the residual soil N increased from 111 to 139 kg ha^–1 for ST and from 112 to 141 kg ha^–1 for CT in 1995 with 202 kg N ha^–1 applied to the previous cotton crop. In 1996, with the same N application to the previous cotton crop, the residual soil N increased from 112 to 143 kg ha^–1 for ST and from 114 to 146 kg ha^–1 for CT. Halvorson et al. (2001) also noted an increase in residual soil N with increasing N rate. According to Halvorson and Reule (1994), residual soil N levels increase when N fertilization rates exceed that needed for maximum yield. Great levels of residual soil N are usually associated with reduction of N₂ fixation by Rhizobium bacteria.

View this table: [in this window] [in a new window]   Table 3. Influence of tillage and N rate application to the previous cotton crop on white lupin dry matter yield, silage IVOMD, NDFt, NDFaf, N, P, plant height, grain yield, and weight of 1000 seeds at Quincy, FL, in 1995–1996 and 1996–1997.

View larger version (16K): [in this window] [in a new window]   Fig. 1. Influence of N applied to the previous cotton crop on white lupin dry matter yields at Quincy, FL, in 1995–1996 and 1996–1997. *, **Significance at 0.05 and 0.01 probability levels, respectively.

The white lupin neutral detergent fiber on a DM basis (NDFt) and neutral detergent fiber ash-free (NDFaf) were greater from the ST than CT system (Table 3). The N application to a previous cotton crop did not influence the NDFt and NDFaf.

Two interactions—year x tillage and year x N application to a previous cotton crop—were observed for N concentration in the white lupin silage (Table 3). For every 1 kg N applied to a previous cotton crop, the N concentration increased by 0.026 in 1995–1996 (Fig. 2). However, no silage N concentration plateau was found for 1996–1997. The results from 1995–1996 agree with López-Bellido et al. (2003), who noted an increase in N uptake in faba bean with N fertilization to the previous crop. Our research showed greater N concentration from CT than ST in 1995–1996, while the difference for N concentration between tillage systems was not significant in the 1996–1997 growing season (Table 4). Averaged across years and previous crop N applications, greater lupin silage N concentration was obtained from CT (27.3 g kg^–1) than ST (24.6 g kg^–1) (Table 3). The increase in silage N concentration under CT could be due to incorporating harvest residues from a previous crop and therefore increasing soil N (Carranca et al., 1999). In faba bean, however, López-Bellido et al. (2003) did not observe tillage effects on plant height. Overall, the N concentration in silage increased with increasing N rates in a previous cotton crop, and greater N may be obtained from CT than ST in some years.

View larger version (12K): [in this window] [in a new window]   Fig. 2. Influence of N applied to the previous cotton crop on silage N concentration in white lupin at Quincy, FL, in 1995–1996 and 1996–1997. NS, no significant at the 0.05 probability level; ***Significance at the 0.001 probability level.

A year x N application to a previous cotton crop interaction was observed for the plant height (Table 3). Plant height increased with increasing N rate to a previous cotton crop in 1995–1996 (Fig. 3). However, no plant height plateau was achieved in 1996–1997. Plant height was also influenced by tillage system (Table 3). Taller plants were observed in ST than CT.

View larger version (13K): [in this window] [in a new window]   Fig. 3. Influence of N applied to the previous cotton crop on plant height of white lupin at Quincy, FL, in 1995–1996 and 1996–1997. NS, no significant at the 0.05 probability level; **Significance at the 0.01 probability level.

View larger version (16K): [in this window] [in a new window]   Fig. 4. Influence of N applied to the previous cotton crop on white lupin grain yields at Quincy, FL, in 1995–1996 and 1996–1997. *, **Significance at 0.05 and 0.01 probability levels, respectively.

View larger version (12K): [in this window] [in a new window]   Fig. 5. Influence of N applied to the previous cotton crop on the seed weight of white lupin at Quincy, FL, in 1995–1996 and 1996–1997. **Significance at the 0.01 probability level.

	SUMMARY

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

	NOTES

TOP NOTES ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION SUMMARY REFERENCES

 
This research was supported by the Florida Agricultural Experiment Station and approved for publication as Journal Series No. R-10190.

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